22RE Random Slight Miss at Warm Idle

[pinemind]

Hi guys,

I'm battling the standard "random miss at warm idle" issue on my 1985 22RE. I've done tons of reading across all forums, and have such replaced and tested items listed below already per the suggestions. No dead cylinder spark (remove spark plug wire test on each cylinder, follows appropriately), and it can run fine at warm idle for 10 to 20 seconds, then a random light miss. You can see below how I've categorized what I've replaced, tested, and what I plan on doing shortly. At a high level, I'll admit I haven't done anything from a fuel system/delivery perspective so those are high on the list to replace. But given the randomness, outside of a bum fuel injector, I don't think the fuel system has much to possibly contribute here.

I have one observation, and I'm thinking I know the answer regarding the TPS. Seeing as these are idle related issues, I focused on the IDL-E2 readings, specifically the one that is not an infinite reading of resistance (0.57mm, <2.3K ohms). When I test this, I get infinite Ohms at 0.57 mm. The highest gap I can put in with the feeler gauge where I get a non-infinite Ohm reading is 0.50mm.

Do you guys think that could be the source of the idle issues? I've ordered another TPS and will be properly adjusting it this weekend, but just wanted a confirmation, as there are still a lot of things I'm going to replace/clean per my lists below and I'd like to actually find the root cause to give back and educate.

Any other insights would be great, given my lists below and explanations above.

What I have replaced/cleaned:
- All vacuum lines with silicone ones and new clamps
- OEM plugs, wires, rotor, cap
- Throttle body gasket
- OEM EGR Valve
- EGR gaskets (block and plenum)
- OEM PCV valve, grommet, hoses
- O2 Sensor (OEM Denso 4-wire for new LCE Header)
- Full new exhaust/gaskets (LCE header to turn down, including cat)
- 1 air intake elbow, all new clamps
- All connectors cleaned with contact cleaner
- Throttle body completely cleaned of carbon

What I have checked (resistance/electrical)
- AFM
- Coil
- Distributor pickup coil
- Cold start injector
- Coolant temp sensor
- Cold start thermo switch
- EFI/Injector Solenoid Resistor
- TPS (IDL-E2 @ .57mm is off, may be a problem)
- Shined light through all intake hoses and elbows to verify no leaks (still need to do spray test as outlined below)
- Timing, on point jumpered and not-jumpered
- No CEL's jumpered

What I need to test:
- IACV (resistance)
- IACV (operation, coolant lines blocked?)
- Vacuum/air leaks w/starter fluid (vacuum lines, intake gaskets, air intake hoses)

What I am planning on replacing (in order, still waiting on gaskets for fuel rail/injector):
- New OEM igniter, quick swap to see if this may be the issue since testing it per FSM is not so simple
- TPS and proper adjustment
- Rebuilt/flow tested fuel injectors
- OEM fuel rail
- OEM fuel filter
- OEM plenum to intake manifold gasket

 

[pinemind]

So I still haven't gotten around to taking off the throttle body and really firming up the TPS adjustment, along with cleaning out the IACV. But, I did fix my random misfire and I'm not 100% sure what fixed it.

A few weeks ago, I got some gas at a shady station during a rain storm. The next day, the misfire was getting worse. So I figure the gas was bad, water in the tank, something. After firing through that tank, crossing fingers at every stoplight, I filled up with some quality gas and dumped in some Redline SL1 fuel injection cleaner. My really bad misfire was gone within a 100 miles, but the random one still seemed to be there.

I mentioned in my other thread that I bought what has to be the last new old stock of a 1985 model igniter. Now, I never tested the igniter because it's not easy to test (need a 5V source, etc, etc). But I also heard that it couldn't cause random ignition problems, and when it dies, it just dies and you can't run your engine anymore. So I installed it, and I swear the misfires are gone. I'm not sure if it was the Redline working it's way through the injectors, but I have to think the igniter played a role. I'm not going to put on the old one to reverse test it even though I probably should. Just going to let sleeping dogs lie. I still have an idle that I think could be improved with the TPS adjustment and the new injectors/fuel filter I need to install, but it's 100% better than before.

 

[pinemind]

I didn't want to have to update this thread in a negative manner, since I've been doing a lot of work, replacing everything including the engine over the past 6 months. However, even after my engine replacement, the slight miss/shake at warm idle still exists.

Since last time, relevant parts replaced:
- New OEM igniter
- Adjusted original TPS again (more on this later)
- Rebuilt/flow tested fuel injectors
- OEM fuel rail
- OEM fuel filter
- Plenum/intake manifold/TB gaskets
- Engine
- OEM Cold Start Timer Switch
- OEM Coolant Temp Switch
- Intake and Plenum professionally restored (hot tanked, threads chased, new freeze plugs, powder coated)

Parts Checked (in addition to above original post):
- IACV: coolant flow is perfect/no blockages, Ohms at 50, slightly open vane at room temp, opens more after 30 min in freezer -> cannot be IACV at this point
- AFM: rechecked this again at the AFM (haven't done ECU yet), all in spec
- TPS voltage/resistance at ECU -> VTA voltage was spotty, not in spec, so I jiggled the connector -> got it back in spec but still random miss -> this is my current hypothesis on what to fix to get this problem nailed down


What's Left (in order of what I think will fix it):
- TPS Connector -> since I had issues at the ECM side for VTA voltage, this is definitely an issue. Will inspect the wiring beyond the connector to the harness and splice in if necessary.
- New OEM TPS on order -> I had ordered the wrong one (-20050 instead of -20060), which bites us 1985 owners as there is a split in production year from 7/1985 to 8/1985 where the TPS model # changes. Mine is production date 2/1985, and all the parts sites show both fit (even Toyota) because you can't enter a production date. Anyone needs a brand new OEM -20050 TPS for a steep discount ?
- Fuel Injector wiring -> going to solder on new connectors, and solder/new wire for the crimped 1 to 2 and 2 to 4 connections
- Fuel pressure regulator -> tests with pinching vacuum checked out, but I'm going to replace it anyway
- Fuel Pump -> no indication it's "bad" but I know it's a NAPA part and I simply don't trust anything but Toyota/Denso for mechanical/electric parts. Lower on the list

Currently, it throws a code 7, which means TPS short or ECU problem. Since the sensor side of the TPS can be adjusted and checks out, and I uncovered that VTA voltage issue, I can only assume the TPS itself is good, but the wiring is bad. Either that or the ECU is toast. So I'm banking on replacing the connector/wiring in the TPS circuit to solve the issue. But I'll still replace the TPS since mine is original 1985. I'm having a hard time trusting the multimeter right now given everything I've checked that hasn't solved the problem.

I still wonder about the AFM. Everyone on forums blames the AFM for everything related to idle issues and starts adjusting things that don't need adjusting, even if it's in spec. Any thoughts that I should find a good used one for the hell of it if it's cheap? I refuse to open it up, as it seems that just causes more problems. Plus, my engine is completely stock replacement, no aggressive cam, porting, boring, etc. So there should be no need to adjust the AFM at all.

Again, any suggestions would help. You can imagine my frustration after replacing the engine and basically everything else under the hood with quality OEM parts, to still have this stupid shaky warm idle and random put, puts.

 

[pinemind]

I got the new OEM TPS in the other day and pulled off the throttle body (P/N 89452-20060). First, I went through and reset the throttle stop screw. I did notice that prior to setting it, there was definitely a bit of a "stick" of the throttle plate requiring some slight effort when manually pulling the throttle linkage. Once I readjusted with slight contact, plus 1/4 turn, I noticed there was no more sticking but there was also no light coming through. So I think this had to be adjusted anyway. I then put on the new TPS and adjusted it per specifications.

The problem is definitely a lot better and the idle shake is not as obvious. But something slight is still there. After pulling the EFI fuse, and driving around for the past day or so, I haven't seen the code 7 come back. However, I'm still unsure that this is just due to how the connector is currently making contact with the TPS/wiring and it just happens to be in the right position when I reconnected it to the new TPS. I'm awaiting the replacement TPS connector, and I will be inspecting the wiring/replacing the connector once I get it in, just for peace of mind.

I still think there is room for improvement, and will be unwrapping the harness to check the fuel injector crimp/wiring as well. It's probably a good idea to just rewire and properly solder those power/ground crimps to the FI"s regardless of what I find, given they're surely to crap out if they haven't already. Just a little battle weary from removing the plenum, coolant lines, fuel lines what seems like on a weekly basis so not in a huge rush now that it's running the best it has.

It's a bit disappointing that the new TPS improved the issue, in terms of troubleshooting (trust me, happy it's running better but ...). While my old TPS was original, it still tested fine and had identical spring back vs the new one. So being able to trust the multimeter on other elements on the truck introduces doubt across the board.

 

[pinemind]

This past weekend, I tore into the wiring harness to investigate the FI splices on power and ground and also replace the fuel pressure regulator. I was hoping to find one or more of the splices in bad shape, but after getting into it, the splices looked fine on all accounts. But I also had some new FI connectors that I wanted to splice in, so I ended up putting in the new connectors, running new wire from the connectors through the splices, and soldering everything. I performed continuity tests after all the connections were made and everything was good. It wasn't that easy doing the 2 -> 4 ground solder with 6 wires, but I got it done. The aftermarket FPR didn't line up that well with the return line connection and threading, but I left it on to see if there would be any difference. Once everything was buttoned back up, I thought I noticed some improvement (like with every other change I've been making). But after a few days of driving, I'm back to where I started with the same slight miss at warm idle.

The good thing is, between the TPS, FPR, and FI splices/wiring, per testing they showed they weren't the problem. So replacing/fixing those areas shouldn't have made a difference. But at this point, I don't have much left to try that could fix the random miss. I did see some excess fuel in the intake runners when I took off the plenum, but the plenum itself didn't have a lot of fuel so I wouldn't suspect a leaky cold start injector. And my fuel injectors are only 1k miles old (bought new/rebuilt from LCE) so I guess there is a chance one or more were bad from the start but it's unlikely.

What's left to try:
1. Swap CSI - I bought a used one off eBay and I'm going to swap it in. If it doesn't change anything, I'll leave it in and send out my original for rebuilding.
2. Fuel Pump - still waiting on some hardware/gaskets and then I'll replace the pump. I haven't tested the fuel pressure but given how it runs outside of idle, and the new FPR, I highly doubt it's a fuel delivery issue.
3. Fuel Injectors - I have my originals I need to send out to Witchhunter. Perhaps I'll try swapping those back in once they are rebuilt? Grasping at straws here.

New Ideas:
1. O2 Sensor - it's a new Denso heated unit to work with the LCE header. I don't get any o2 sensor codes, but I want to test it to see how it's operating. With the discovery of fuel in the intake runners, I want to make sure it's not running too rich.
2. Vacuum Leaks - I've tried the propane method, but may end up taking it somewhere to get it smoke tested just for peace of mind.
3. Exhaust leaks - Another stretch as I don't hear anything obvious, but this could be causing an issue if there's a leak especially near the o2 sensor where that pipe connects to the catalytic converter
4. Ignition Components - again, these are all new OEM (spark plugs, wires, cap, rotor, coil, igniter). I doubt these are the issue.
5. Distributor/AFM - I may pick up some used ones off eBay and just swap them in to see. AFM tests fine but I've heard them still not performing well especially if they are old/original even if they test well.
6. ECU - picking up a spare to swap in for the hell of it

It's definitely frustrating as I have nothing left to test that isn't in spec and now I'm just throwing parts at it. I went through the entire EFI troubleshooting for voltage and resistance as well and everything was in spec, except for the Ne -> E1 resistance which showed open. I ran a continuity test from the ignitor connector at Ne back to the ECU's Ne pin, and no issue. All other E1 tests at the ECU were in spec so I know E1 is good. So maybe there is an issue in the wiring there in Ne between igniter and ECU, but I've searched and can't find anyone who confirms this resistance reading has caused problems.

 

[Melrose 4r]

I am following your posts closely. Thanks for the excellent documentation on this subject. My truck has the warm idle miss also. Since it mimics a poorly adjusted carburetor i too thought an injector was leaking and had them rebuilt(not the cold start, though). It did not help. There is one piece of data that may be a clue. I notice it doesn’t miss when the a/c is on and the idle raises slightly. I hope you can crack this.

A couple more thoughts on this topic. When i was about 18 my dad had a brand new 86 Toyota 4x4 pickup and mom had an 84 Celica Gts, both with the 22re. I used to drive and maintain both of them. Both were run up into high miles over the years and neither one ever exhibited this warm idle miss. My dad, being a super car guy would have lost his mind if they did. I know, small statistical sample, but this makes me think the problem has more to do with age than actual mileage. I quickly checked a Celica forum toyotacelicas.com and do not find reports of the idle miss in 22re Celicas but will keep reading.

 

[Melrose 4r]

A couple more thoughts I plan to try as soon as i can.
1) put the timing light on each plug wire, look for inconsistent flashing while the miss occurs. Rule out ignition.
2) the AFM can be adjusted rich or lean by removing the cover and turning the cog 1-4 teeth in either direction. In the 90’s, I had(bought) a TRD white paper that explained how to do this and 2) how to block off your EGR function using only a BB.

I know you said above you didn’t want to open it but...now that i’ve read for a couple hours, i think this is going to be the answer.

Here is further support for the idea of AFM adjustment.
22RE Why your idle is rough or missing - YotaTech Forums
This guy makes a good point about fuels being different 1980’s vs. now.
AFM ADJUSTMENT TO CORRECT AIR/FUEL RATIO - YouTube

 

[pinemind]

A couple more thoughts I plan to try as soon as i can.
1) put the timing light on each plug wire, look for inconsistent flashing while the miss occurs. Rule out ignition.
2) the AFM can be adjusted rich or lean by removing the cover and turning the cog 1-4 teeth in either direction. In the 90’s, I had(bought) a TRD white paper that explained how to do this and 2) how to block off your EGR function using only a BB.

I know you said above you didn’t want to open it but...now that i’ve read for a couple hours, i think this is going to be the answer.

Here is further support for the idea of AFM adjustment.
22RE Why your idle is rough or missing - YotaTech Forums
This guy makes a good point about fuels being different 1980’s vs. now.
AFM ADJUSTMENT TO CORRECT AIR/FUEL RATIO - YouTube

Thanks, I'll definitely consider these options. I believe I've moved the timing light across the plug wires before and didn't see any change in flashing. As far as the AFM, I'm more inclined to mess with it if I have a spare. I've seen bad reviews of DOA's on Cardone remanufactured units. However, there is one for sale on PartsGeek by a different manufacturer, that has 5 star reviews, with someone specifically mentioning they used it during their 1987 4Runner restoration in 2019 and it's working perfectly. It's pricey, but I'm wondering if it's not a bad route to go down. Used off ebay they are almost as much money.

And this fits into your age comments as well. I saw that Yotatech thread, and the reason I shy away from adjusting the AFM, was that person had an upgraded cam. My whole goal in this restoration is to have everything back to stock, hence the replacement of all parts that I can with OEM. My rebuilt engine from Yota1 is stock as well. So in terms of age, outside of wiring and my ECU, there's not much left that isn't new. So I assume I'm naturally taking age out of the equation as I replace parts, sure up wiring etc. Does that make sense?

Same goes for timing. I've seen Jim at 22RE performance say that retarding back to 3 or 2 degrees has helped him fix issues with customers. So I may give that a shot.

A few updates:
- Tested my CSI for leakage: No issues, so that whole circuit is fine mechanically and electronically and can be ruled out
- Tested o2 sensor operation: Via the Vf connector, I can see it properly oscillate between 0.1V and 0.85V about 8 - 10 times in 10 seconds. I haven't read the stored value yet as I wasn't sure when I was testing it how to get that. But at least I know the upgraded 4 wire sensor (on my 1 wire OEM truck) is functioning properly electronically. It was always a question after hooking it up to the various ground and power locations).
- New distributor - I've got a new Spectra distributor coming in today. I've read a bunch of threads and some seem to indicate a new distributor has fixed a similar problem. Not a new pickup coil, which mine tests out fine. But mechanically some play in the distributor may cause enough discrepancy to not fire the cylinders consistently and on time. It's a shot and it can go back to Amazon if it doesn't fix it.

Possible break through/clue:

Miss is not only at idle - so last night, I had it idling after being run for a good 30 minute drive. I was moving wires around (AFM, other connectors, etc) to see if something affected it). I've got it set to around 750 to 800 for normal idle and that's where I see the random shakes/misfires normally. However, I was pulling on the throttle linkage and raising the RPM's slowly, I'm guessing up to at least 2k RPM's. I definitely still see the shakes up until almost 2k RPM's. So ... the miss is not only at idle, I just can't notice it as much when I'm driving, or never bothered to slowly rev it while under the hood. Usually I just rev it quick and see the shakes go away and assumed it was just at idle.

What do you think this tells me about the problem? Curious if you try the same thing, does your shake/miss continue up through the 1k's of RPM's like mine, which would indicate it's not strictly an idle problem? But it's definitely a "warm" problem, because on cold starts, prior to engine going into closed loop and up to temperature, I don't see these shakes (while it's idling around 1k to 1500k).

Long Shot - Air in coolant?

I've had my plenum and various coolant hoses off so many times in the past 3 weekends I've lost count. And everytime, I lose a little coolant before I can shove a bolt in to stop it. Is it possible that air in the coolant is causing these issues, and I just need to properly raise it, run it with a spill-free funnel and get the air out? I only did this once after getting the new engine in and never went back to check. But I know air bubbles can also cause issues with not getting heat in the climate system, and I don't have an issue there.

Last Clue - Timing jumps to match shakes/misfires

I think this is normal, but when checking timing, it's normally right on 5 degrees BTDC. Whenever I get one of these misfires, it will shake between 7 and 5. It's hard to tell but it definitely doesn't stay right on 5 when these events occur. I'm pretty sure this is just an indicator of the problem I have. It's not jumping something crazy like 10 or 20 degrees off the crank indicating a timing chain is off (which I checked when I adjusted the valves and it's spot on).

The Randomness Explained

If I'm driving for awhile, then come to a stop, I watch the gear knob and listen like a hawk. There are some times at a stop, when it can go 1 to 2 minutes running perfectly. But it seems, the longer I sit, those random shakes start to occur in more successive and shorter time periods, until they become "randomly consistent."

There's other times, where after a warm start, it's just doing the shake right from the get go if I let it idle, and it occurs randomly but on a quicker time series gap.

So that's what I mean when I say random although there are some discernible patterns to how that randomness occurs.

 

[Melrose 4r]

I think my truck does behave like yours with respect to raising the idle to 2k or so and still exhibiting the “miss”. I am away from my truck until the weekend but can do more troubleshooting then.

I don’t think slightly low coolant or bubbles in coolant would cause any probs.
I’m now personally convinced enough to open my AFM and adjust it. So i’ll be happy to report back after the weekend.

I have a wideband 02 sensor in another car that i could use to see exactly what is going on at the time of the miss. I use it for carb tuning on my old,old car and to me it seems just like it is dripping fuel(too rich) at idle. The 02 should show if we are rich or lean. Some of the people claiming great success with AFM adjustments on other Toyota engines are leaning them. 22re may need to be richer.

How do your plugs look? Mine look lean.

 

[pinemind]

I think my truck does behave like yours with respect to raising the idle to 2k or so and still exhibiting the “miss”. I am away from my truck until the weekend but can do more troubleshooting then.

I don’t think slightly low coolant or bubbles in coolant would cause any probs.
I’m now personally convinced enough to open my AFM and adjust it. So i’ll be happy to report back after the weekend.

I have a wideband 02 sensor in another car that i could use to see exactly what is going on at the time of the miss. I use it for carb tuning on my old,old car and to me it seems just like it is dripping fuel(too rich) at idle. The 02 should show if we are rich or lean. Some of the people claiming great success with AFM adjustments on other Toyota engines are leaning them. 22re may need to be richer.

How do your plugs look? Mine look lean.

I just replaced my plugs with the FSM recommended Denso's (W16EXR-U), as my previous set were in my motor during the head gasket leak (they only had 1500 miles anyway but you could tell there was an internal coolant leak). And I've only got about 500 miles on these plugs on the new engine. I will check sometime this weekend or next.

Flashes across all spark plug wires with the timing light are consistent across ports. They are OEM Sumitomo's, with about 3k miles on them so I don't see an issue with plugs or wires at this point. Cap and rotor are 3k old OEM's as well with new o-rings. I'm still thinking it could be the physical distributor given the timing light/mark jumping around, which is messing with the Ne signal (see below about the ECU resistance test failure on that signal to E1). Especially since the Ne is sending the RPM signals back to the ECU to calculate A/F ratio. But still ... why does this only happen in closed loop and not in warming up when I get no misses at a slightly higher RPM (~1200 RPM)? I was under the impression that Ign and Igf signals are only used in the first few seconds of starting until the ECU can get a good Ne signal direct from the distributor via the ignitor for RPM's. Unless Ne is ignored until it's warmed up and goes into closed loop, but I think that's a false statement from what I've read. Again, distributor is probably a "throw a part at it" attempt at this point.

o2 sensor update: I tested again to get the learned Vf signal from the ECU after driving around for 30 minutes this morning and I see 0.43. Since my active oscillations were between 0.065 and 0.85, this seems to fall just above the midrange (57% in the range) which according to some Vf documentation should be perfect with a 2%-3% error correction bringing it back toward the exact middle of that range. I can't seem to find a way to test the o2 sensor to get the 1V to 5V ranges per the FSM as it requires some SST on the large connector. But I'm assuming I would see a similar set of readings for the oscillations and learned value, just on a different scale.

Vacuum Measurement: I decided early this morning to pick up a vacuum gauge just to check there. Plugged into the P/S port on the plenum and got 20 Hg. While the misfires happen, it would waver a bit, but nothing beyond a fraction of Hg. I think 20 might be a tad high (most posts I've seen are 18-19), but it's not low, which would indicate a vacuum leak somewhere. It's also a cheap Harbor Freight gauge so I'm taking 20 to be 18-19 ...

Another thought I had about the "age" question. I have a spare ECU coming in and I will be tossing that in there. Theory here is, it's good to have a spare as the original is going on 35 years old. And, unfortunately, there are countless "misfire 22RE" threads across the Internet where after 10 pages of troubleshooting, someone says "I swapped ECU's, it's fixed." and that's the end of it. It's like resetting the home router or cable box by rebooting it type of effort, but I've always wanted a good spare should something ever happen to mine.

I still want to investigate the Ne -> E1 open resistance I am getting. FSM says 0.14 - 0.18 k-Ohms. I forgot to slice open the plastic which encases the 3 wires (including Ne) from the ignitor connector back to the main harness in the plenum/intake when I was resoldering/wiring all the FI connections last weekend, and just lazily checked continuity which was fine. Still haven't found an answer as to whether that reading matters or not. 1 or 2 threads out there with people with a rough idle, saying they also had open resistance there on that check, but no follow-ups or answers as to whether it matters. I don't want to dig into that harness again unless I can get an answer as to whether it's worth it. By all means, yell at me if I shouldn't be ignoring this I'll happily run a brand new wire all the way from the ignitor connector's Ne all the way to the ECU. I'm just not wild about trying to remove pins from these various connectors, as I haven't found a good writeup on how to do it yet and would hate to break these brittle plastic connectors.

I won't have any updates for the next few days as I'm waiting on parts to do the following repairs/troubleshooting:
- New distributor
- Denso fuel pump and associated hardware
- EFI Solenoid (issue below)

The EFI solenoid is another one like the Ne -> E1 which I'm not sure is causing a problem, even though it's failing the test. FSM says 2 - 3 Ohms. I'm consistently getting 3.3 Ohms on mine. Is this really bad at just 0.3 Ohms out of spec? No idea. Stethoscope on all injectors has them firing at warm idle without problem. But a used one wasn't that expensive, so just awaiting that to swap it in/test the Ohms. Input here from folks would be nice.

That's really all I have left to try at this point. Grounds have been checked, cleaned, more times than I can count. I may go through and super clean all the connectors related to EFI with contact cleaner again as well.

 

[pinemind]

Due to the sweltering heat this weekend, I took the path of least resistance and swapped in the spare used ECU I obtained off eBay. Initial results after driving around for 30 minutes seemed to indicate it was running better. But like this problem has always been, it can seem fine for awhile, then drop back to it's random misses and shakes. So the ECU definitely didn't change the situation at all.

Hoping I'll get around to the fuel pump install this week, not holding my breath that will fix anything. And I still have the new distributor to try as well.

 

[pinemind]

Threw a refurbished AFM from Fuel Injection Corp (on Partsgeek) in the 4Runner last night. I bench tested it and it passed without issue. My old one was fine, but we're in "throw parts like a dart" mode right now. No change at all, negative or positive (cold start, then warmed-up closed loop).

I still was never comfortable about the O2 testing, since I only tapped into the Ox single wire diagnostic port to get the < 1 volt based readings. I found some great older articles on Vf testing, and decided I wanted to get access to the Vf signal to match the FSM tests (0V - 5V scale) as those documents give indications on what is lean vs rich in terms of the Vf static reading, and may indicate what could be wrong. Note my sensor has never thrown a code.

First, I unplugged the o2 sensor and ran it. I should have done this first as it runs great (just like on cold starts as it forces it into open loop). But as always, run it for awhile with a change you think solves the problem, and after about 15 minutes of driving, it's back to it's old put put's out the tailpipe. I was reading somewhere that even though it's technically in closed loop with the o2 unplugged, eventually there will be some tweaks to the base mapping after an extended period of time, thus re-uncovering the original issue. At first I thought "awesome, it's my o2 sensor or my wiring" but then I was crushed.

I found the Vf wire in the larger, 3 wire diagnostic connector on the driver's side fender. I knew it was there but had no idea which wire was which. This is for early 22RE's and the only documentation I could find with pictures was for later ones with the diagnostics in the fuse box. 1985 FSM doesn't even have the large o2 sensor diagnostics plug in the wiring diagrams. I found a 1986 wiring diagram pdf somewhere and it showed the o2 connector and the color/name of the wires. It has Vf (grey), E1 (brown) and B+ (black).

1986 22RE EFI Wiring Diagram - with o2 Diag Connectors

So I found this awesome Altavista-era website that had some great details on voltages for o2 sensor testing:

Toyota Vf1 - o2 Sensor Detailed Testing

I ran the truck for about 15 minutes to get it solid in closed loop, and to make sure after the o2 sensor unplugging it was relearning and storing a new value. With the DVOM, and the TE1-E1 diag connector jumped, I was able to see it fluctuate between 0 and 5 volts. Normal. Then I disconnected the TE1-E1 jumper to get the stored correction value: 3.52.

If I look at the scale here on the site I referenced, 2.50V is considered perfect with no corrections needed by the ECU to adjust fuel up or down. What surprised me, is that at 3.52V, it's actually on the lean side (prior to correction). However, the guide says it's still within normal. All the while I thought one of the issues could be a leaky injector, and that's now been ruled out. But the culprit now lies in air issues: vacuum leak, exhaust leak, etc. I don't think it's an actual o2 sensor issue, though I may try and fish out my old 1 wire o2 sensor and see what happens there.

I don't really think this told me much, since it's in the realm of normal. And I've definitely done my vacuum leak checks. My exhaust could be something to look at, as I do use the clamps that came with the LCE header and pipe and I saw some soot around one of the clamps pre-o2 but it's as tight as I can get it. I have to take it next week to get a hanger re-welded, so I'll see if they can do a test for leaks while it's there. I should just get it all welded up and be done with it, especially that small pipe with the o2 and it's connectors.

Still to try:
- New fuel pump
- New distributor
- 1-wire o2 sensor

Thoughts?.. Prayers (at this point) ?

 

[Melrose 4r]

Couple quick comments.
My truck uses the one wire O2 sensor and it’s only about 1 year old. It came with a box of spare parts. I don’t even remember why i swapped it with the one that was in there, other than it was new, but there was no change.

It’s been way too hot to get under the hood but i did drive my truck last weekend about 50 miles with the A/C on the whole trip and no misfires the entire time. So something about raising the idle cures the misfire.

 

[pinemind]

Couple quick comments.
My truck uses the one wire O2 sensor and it’s only about 1 year old. It came with a box of spare parts. I don’t even remember why i swapped it with the one that was in there, other than it was new, but there was no change.

It’s been way too hot to get under the hood but i did drive my truck last weekend about 50 miles with the A/C on the whole trip and no misfires the entire time. So something about raising the idle cures the misfire.

Yeah I currently don't have the A/C assembled. The condenser from Denso is backordered until mid-October. So I don't have any A/C parts to get in the mix. I did however noticed my A/C idle-up VSV is not testing in spec at all (open resistance between the two contacts). So while waiting for a new one, I capped off the two vacuum line connections at the A/C/P/S diaphragm on the intake just to see if there was some issue there but it made no change.

Updates:
- Installed new distributor/cap/rotor (non-OEM), set air gap to match OEM one to 0.30 mm. No change in behavior at all.
- Installed new Denso fuel pump. Previous one in there was a Denso unit. I was actually hoping it was a cheap one that may have been causing the issue. But I replaced it anyway, no change in behavior.
- Swapped in a used EFI solenoid I got off eBay. It didn't test in spec (like my current one). No behavior change.
- Did a prolonged series of tests pulling individual spark plug wires and watching the tach on the timing light. This is hard to audibly hear any differences, since running on 3 cylinders masks the slight misfire and shakes I would normally see. The only thing I noticed, was the range in idle variation was about 15 to 20 RPM's across all 4 test scenarios. When all 4 are plugged in and it's doing it's random shakes, I get a 30 - 50 RPM fluctuation. I think this was inconclusive from a test perspective as I couldn't hear or see anything that points to a particular cylinder.

New Theories:
- Fuel Pulsation Damper: This is the only part on the EFI fuel delivery side that I haven't replaced. Research shows these don't usually cause idle/running issues (that's reserved for the fuel pressure regulator), and if they fail, you basically just get a massive fuel leak. However, I noticed from pictures, mine was missing this plastic cap, but more importantly, was missing a set screw in the end of it. Apparently, the screw is set from the factory to control pulses from the fuel pump, and if anything, affects abrupt changes in fuel delivery (not idle). Strangely enough, if this screw is gone, it's supposed to leak. Mind doesn't leak, but I'm starting to think if it's not damped correctly, if the fuel delivery isn't metered properly it could be an issue. Regardless, the part is fouled up and I ordered a new OEM one to take this out of the equation. If the screw is gone, it allows the diaphragm to go in and out more than it should.
- Exhaust Leak: I have the LCE header and it's clamped between the header, o2 pipe, and catalytic converter. I noticed some black soot on a clamp before the o2 sensor, but I don't really hear any noticeable leaks. This could definitely cause a problem especially since it's pre-o2. But I tightened up the clamp, moved it around a bit in different positions, and it hasn't changed anything noticeable. I need to get a hanger re-welded so I will ask the shop to check for exhaust leaks, as I don't have a good way to test for minute leaks on my own.
- Fuel Injectors - Flow not matched or slightly leaking injector - Although these are new from LCE, and they are rebuilt OEM, I don't have any confidence from their product description as to how these are tested. I received no sheet indicating the flow or patterns across all 4. Also, I waited about 8 months after ordering these to installing them, and I've heard that's not a great idea and they should be installed within 30 days of being rebuilt. I found another company that provides OEM Denso injectors for a good price (MotorMan), and they also include test and flow sheets. Furthermore, they flow test and lubricate the set on order so they're not sitting around in a warehouse since who knows when. This would be my last ditch effort, but I may bite the bullet and order 4 of them.

 

[Melrose 4r]

My very first thought was a drippy injector since the stumble in the idle mimics a poorly adjusted carb. So i had mine flow tested and cleaned by Hurst Injector Service in Fitchburg MA for a very reasonable cost and quick turn around. Two injectors were underperforming and were restored to full operation, but i could not tell any difference and my couple mileage calculations since then actually seem worse by a couple mpg highway.

 

[pinemind]

I think, it's finally f@#$%ing fixed. Let me be clear: I haven't nailed down what fixed it but I'll explain below.

What do I mean by fixed?
- The random misses at warm idle are gone. I ran it for about 5 miles (it was already warm), then sat there for 30 minutes with my timing light tach adjusting the idle screw to nail down 750 RPM.
-The idle RPM range is now 10 to 15 in fluctuations (i.e the extremes it will hit will be 745 and 755, but mostly stays in a 5 RPM range). Before, it was easily a 50 RPM extremes fluctuation, sometimes 60.
- My gear knob, the ultimate indicator, now does not have the violent shudders randomly to match the put-put, put ... put's out of the exhaust.

What did I do to fix it?
1. I ordered a Denso 1 wire o2 sensor to take my heated 4-wire out of the mix, soldered in a longer wire, and hooked it up. This did not make a change. I did have to run it a bit since it's not heated as I took out the EFI fuse to reset things. But once it was warm, the misses were definitely still happening. I left this in there for now (more on that later)
2. The broken pulsation damper - As stated above, I noticed it was missing a screw. Normally this only exhibits problems on acceleration and not at idle from what I've read. But, seeing as it has been the ONLY BROKEN PART in the entire EFI system (as you know everything else tested out fine regardless of me replacing it all), I ordered an OEM one. I put this in and had to run it a bit to get the shakes out (not quite sure why). Went around the block a few times and as I mentioned above, sat there with a tach for 30 minutes. No more misfires and the tighter idle RPM fluctuation. I am claiming victory as this problem would always manifest itself at idle within 30 seconds of stopping. Through all my changes, when I thought I fixed it, it would come back within a minute or 2 of stopping.

So ... damper or o2 sensor? I'm going obvious on this one and saying it's the damper. It was freakin' broken and I replaced it last! No mention on any thread that the fuel damper has ever caused erratic idles, it's always the FPR. I will put my heated o2 sensor back in, since it should be there and will need to be there in the winter. I'll be trying this out tomorrow morning once everything cools. Once that's done, back on goes my OEM distributor, OEM AFM, and OEM FPR (well, not the FPR, I'm done taking the plenum off for the 1000th time for awhile).

But for right now? Victory lap and a beer :beer:

I'll update tomorrow when it breaks again ... no ... positive thoughts ... I mean, when I confirm it was the damper Sorry, bad habits die hard.

 

[pinemind]

Not fixed, kill me.

Swapped back in 4-wire heated Denso o2 to get it back to original configuration. Misfires returned (pulled EFI fuse before for 15 min) even after driving around for 20 minutes.

Hoping it was the o2 sensor, put in the new 1 wire Denso I had it when I "thought" it was fixed ... misfires.

Interesting data points:

- After putting in the 4-wire this morning, and driving around, the idle was low (650 RPM). I left it last night with the 1-wire and it was right around 750 RPM. So I had to adjust the idle screw to get it back up to 750 ... weird.
- When I unplug the 4-wire o2 sensor once it's warmed up, the idle raises to about 900-950 RPM and the misfires are basically gone.
- When I unplugged the 1-wire o2 sensor, no change in idle, no change in misfires. So it's in open loop, not throwing an o2 code on a brand new sensor, assuming it's reading the o2 sensor fine, and misfiring. I guess back to the fuel injector theory or leaks (vacuum or exhaust).

So what happened last night? I have no clue. What I didn't test last night was pulling the o2 sensor connection with the 1-wire while it was idling properly. My guess? It would not have changed.

 

[HulkHagan]

Hey I’m so sorry to hear about your issue. I was reading on other forums that this problem can commonly be traced to a vacuum leak in the brake booster diaphragm. These old boosters tend to fail so it may be worth swapping it out along with the booster vacuum line. You can test your brake booster for a vacuum leak by pressing the brake pedal all the way down with the truck running, and then shutting it off. It should allow you to continue pressing for 30 seconds, but if it’s bad, it will force your foot back up pretty quickly. There’s a valve on the booster that you can test as well, where the vacuum hose attaches. It should only allow air in one way. From what I’ve read though, the booster diaphragm is the more likely culprit. Best of luck!

 

[HulkHagan]

Also, Toyota doesn’t make these boosters anymore so you’ll have to get an aftermarket one. I wouldn’t trust an old one even if it is oem. People tend to like Napa’s though. Also, you can do a direct bolt on of a T100s brake booster. It’s a bit thicker so it will give you better braking power supposedly. I’d go to Napa and ask for a brake booster without ABS for a 96 T100 4wd.

 

[Jram100]

Reviving this thread. Obviously a very thorough search for a solve to this problem.

Experiencing the same issue, Did you ever find the gremlin responsible?