3.4 1999 hard starting, stumbling, and not wanting to rev

[AntleredRuin]

Alright, so first off, I apologize if any of the below mentioned issues has been already addressed. I've found threads that were related while I was getting to my 15 post count newcomer quota, but never with the exact same symptoms. I also apologize for the length of the post; I just want to answer any questions people may have up front.

So I'm not new to Toyota, but new to 4Runners. I just bought my 4Runner a couple weeks ago and I’m trying to figure out a few issues that it started exhibiting after I bought it (of course). 1999 Limited 3.4 2wd Automatic. 133,000 miles.
Symptoms:
1) Hard starting when warm. I have to give it gas as it starts or it dies immediately.
2) Cannot rev past 3000 when in gear. It can rev to 5500 just fine while in park, but if I change to drive, reverse, neutral, etc, it
cannot rev. I’m able to get up to 4th gear just fine while driving (just takes a while) so I don’t think it’s the transmission.
3) It will sometimes stumble/stall if I accelerate too fast from a dead stop. I’ve noticed that this does NOT happen for about 24
hours if I remove the negative battery cable for a few seconds in the morning. Seems like a computer/sensor error.
4) Horrible gas mileage (haven’t measured it, but I can near see the gas gauge move)
5) Occasional VERY strong gasoline smell.

Suspects (possible combination):
1) Bad/Dirty Crankshaft Position Sensor
2) Bad/Dirty Camshaft Position Sensor
3) Bad/Dirty Throttle Position Sensor
4) Bad/Dirty 02 Sensor
5) Bad/Dirty A/F Sensor
6) Bad Catalytic converter
7) Bad Fuel Pressure Regulator

I’ve changed the fuel filter, changed the spark plugs (NGK: BKR5EKB-11), wires (NGK 4412 TE66), removed and cleaned the Throttle Body, IAC, TPS, and the MAF. I cleaned them with all the appropriate cleaners, etc. I did not touch the MAF sensor, just sprayed it down with cleaner.
I know the MAF is not bad. While the 4Runner was running, I unplugged the sensor. It died instantly. I was able to get it restarted, but it idled horribly and sputtered all along the RPM range (still could not pass 3000)
I think that all of the afore-mentioned suspects are original, so are probably due for replacement soon anyways, but I’d rather not chuck money around just because. On Amazon, each of these pieces go for around $100, so replacing all of them at once could get pretty costly.

I DID get a CEL the second time it stalled (P0172) but it went away by itself after a few miles and has not been back for about 300 miles. Because of this, I'm not sure the suspects in the CEL are actually the issue, or if it came on BECAUSE the car stalled. Does that make sense? The code also does not explain all the symptoms.

A couple of questions also:
1) How do I test the different sensors to tell if they are bad?
2) Where is the crankshaft position sensor? I’m assuming BY the crankshaft behind the water pump?

Any help would be much appreciated.

 

[AntleredRuin]

Bump

 

[gamefreakgc]

No need to be apologetic about asking for help. That's what this forum is for right? Besides, I'd rather you write down all that you've done so far rather than post the annoying "4runner dosent go fast plz help" sort of posts.

You've obviously worked on the usual suspects to no avail. I would not ignore that P0172 code though, that will not come on because it stalled. I think you have a fuel delivery issue that either related to the MAF, bad injectors or fuel pump, or maybe the TPS. The MAF controls the fuel/air mixture which could through the P0172.

When you said you removed and cleaned the TPS, what did you do? It does not need to be cleaned. Did you replace it to the factory marks (I can't remember if you can adjust the TPS by rotating it, might be mixing it up with my 91).

I would highly recommend ruling out the MAF completely. They can cause all sorts of issue even without throwing a code. I say this because I had a non-start issue which turned out to be the MAF. No codes though. Do you have a friend with a 4Runner you can swap parts with? If not, you can grab one from a junkyard for cheap and most have return policies for credit. If not, you now have a spare. Be happy you have the cheap version, the MAF's for the 96-98 are $700 from the dealer, $300 aftermarket!

 

[Illicitdream]

Agreed^. I would still try and swap a good, even used MAF out and see how it runs. Mine stalled and bucked upon acceleration for a year before I finally bought a MAF and that eliminated my problem immediately. I also would look at fuel pressure as stated above. I had similar symptoms from my 98 rodeo and it was my fuel pump going out. Have you run an injector cleaner such as seafoam through the injectors? That might help clean them up. The MAFs on our 4runners are also used in camrys and I believe another Toyota model... Just FYI.

 

[gamefreakgc]

Agreed^. I would still try and swap a good, even used MAF out and see how it runs. Mine stalled and bucked upon acceleration for a year before I finally bought a MAF and that eliminated my problem immediately. I also would look at fuel pressure as stated above. I had similar symptoms from my 98 rodeo and it was my fuel pump going out. Have you run an injector cleaner such as seafoam through the injectors? That might help clean them up. The MAFs on our 4runners are also used in camrys and I believe another Toyota model... Just FYI.

I was going to suggest that but wasn't sure on the 99-02 sensors, do newer Camrys have the newer style (non-turbine looking) MAFs like the 4Runners? My current tubine-looking MAF is from a V6 Camry since it was half the price as a 4Runner MAF from the dismantling yard.

 

[Illicitdream]

I was going to suggest that but wasn't sure on the 99-02 sensors, do newer Camrys have the newer style (non-turbine looking) MAFs like the 4Runners? My current tubine-looking MAF is from a V6 Camry since it was half the price as a 4Runner MAF from the dismantling yard.

Yes, the newer camrys have the newer style MAF just like the 99-02 models. A cheap suggestion is to find a reliable seller on ebay and buy a used MAF for cheap, as long as they have a return policy. When you get it in, spray it down with CC MAF cleaner and then plug it in a fire the 4runner up. I Believe the newer camrys with the same MAF as the 99-02 4runners are years 02-06.

 

[jeremyc74]

2) Cannot rev past 3000 when in gear. It can rev to 5500 just fine while in park, but if I change to drive, reverse, neutral, etc, it
cannot rev. I’m able to get up to 4th gear just fine while driving (just takes a while) so I don’t think it’s the transmission.
3) It will sometimes stumble/stall if I accelerate too fast from a dead stop. I’ve noticed that this does NOT happen for about 24
hours if I remove the negative battery cable for a few seconds in the morning. Seems like a computer/sensor error.
4) Horrible gas mileage (haven’t measured it, but I can near see the gas gauge move)
.

These are classic symptoms of bad fuel pressure. It can be other things, but in my experience when a fuel injected vehicle will rev in neutral but won't run right under load it's always been a fuel problem. It's generally low pressure for one reason or another. Could be a clogged filter, or a bad regulator, or I just had a line on my RV that was out of place and got pinched between the shock tower and floorboard and flattened out. It did EXACTLY what you're talking about.

The first thing I'd do is put a fuel pressure gauge on it, and don't just watch it while you're sitting still, you need to drive around. You have way too many things that are possibilities to just start changing parts. You need to narrow the list substantially, and making sure the fuel pressure is right is an easy first step. I suspect you have a bad regulator, but it has a vacuum bias, so it could also be a vacuum issue that's effecting the fuel pressure.

 

[AntleredRuin]

I have a co-worker with a '99 as well, so I'll see if I can talk him into letting me try his MAF for a few minutes. Anything I need to warn him about when I reinstall it back on his? Reset the ECU, or just plug and play?
I'm seeing a TON of MAFs on Ebay for $30 or less. Everything I've heard though indicates at least a few hundred. Are these ones ok?

I did change the fuel filter and it was definitely dirty. The fuel pressure regulator is on the back behind/beneath the intake plenum, correct?

I've run a bottle of STP Fuel injector cleaner through the tank once since I bought it. I've been doing this every oil change on my '03 Rav4 since I bought it 5 years ago and it still purrs.

All the vacuum lines look to be good. There is a tear in the 3-way air intake hose that's duct taped shut. The tear does not even go all the way through the hose, so the tape is more of a preventative.

When you said you removed and cleaned the TPS, what did you do? It does not need to be cleaned. Did you replace it to the factory marks (I can't remember if you can adjust the TPS by rotating it, might be mixing it up with my 91).

I removed it from the TB when I was cleaning it, along with the IAC. It did not look like a part that needed to be cleaned but I figured it would not hurt. I just sprayed it with TB cleaned and air dried it. I replaced it the way it came off (I think). The little rotatable inside would not line up right with the 'tooth' on the TB and the mounting screw holes at the same time, so I put the TPS on the 'tooth' and rotated slightly to line up with the screws. It only rotated one way, and I made sure to mount it facing the same direction as when it came off.

 

[gamefreakgc]

I removed it from the TB when I was cleaning it, along with the IAC. It did not look like a part that needed to be cleaned but I figured it would not hurt. I just sprayed it with TB cleaned and air dried it. I replaced it the way it came off (I think). The little rotatable inside would not line up right with the 'tooth' on the TB and the mounting screw holes at the same time, so I put the TPS on the 'tooth' and rotated slightly to line up with the screws. It only rotated one way, and I made sure to mount it facing the same direction as when it came off.

Yeah, that sounds right. On the older rigs it was possible to put it on wrong like you saw so just checking. A bad TPS on the old 4Runners would not throw a check engine light, just be really bogged down. I think the newer 3rd Gens don't have that problem as much.

 

[AntleredRuin]

Yeah, that sounds right. On the older rigs it was possible to put it on wrong like you saw so just checking. A bad TPS on the old 4Runners would not throw a check engine light, just be really bogged down. I think the newer 3rd Gens don't have that problem as much.

How would I test a bad TPS? (I guess I could always ask my coworker if I could borrow his also)

 

[AntleredRuin]

Alright, so I don't know if it's fixed, but there's definitely an improvement.
During lunch I adjusted the throttle and tranny kickdown cables and took it for a spin. They were both about as 'loose' as they could be, so I moved them to the other end of the spectrum. What an improvement!
The 4Runner started right up (and it was warm too!) and I was able to actually pull out into the street without waiting for a mile long opening! I floored it several times and it flew right past 3000 without any issue.
It didn't sputter or stall at all (has not for a couple of days now). Maybe the ECU finally learned my driving habits after the resets?

I didn't smell any gas at all (but to be fair, it's a random occurrance; maybe it needs time), and I'm still not sure about mileage as its only been a couple hours.

 

[gamefreakgc]

How would I test a bad TPS? (I guess I could always ask my coworker if I could borrow his also)

I'm not sure there is. The TPS is more of a long shot, since it wouldn't break unless it had a reason to. I was just asking about it because normally it's not touched at all. Was just making sure you didn't do something silly like soak it overnight in cleaner or something like that lol.

Alright, so I don't know if it's fixed, but there's definitely an improvement.
During lunch I adjusted the throttle and tranny kickdown cables and took it for a spin. They were both about as 'loose' as they could be, so I moved them to the other end of the spectrum. What an improvement!
The 4Runner started right up (and it was warm too!) and I was able to actually pull out into the street without waiting for a mile long opening! I floored it several times and it flew right past 3000 without any issue.
It didn't sputter or stall at all (has not for a couple of days now). Maybe the ECU finally learned my driving habits after the resets?

I didn't smell any gas at all (but to be fair, it's a random occurrance; maybe it needs time), and I'm still not sure about mileage as its only been a couple hours.

The cable adjustments help a ton, mine were so slack when I got my 4Runner it would never downshift at all! However, that would not affect sluggish feeling over 3000 RPM (maybe below that) or hard starts. Might have just been because of the battery reset like you said but once the troubled sensor acts up again you'll probably be back to where you were before.

 

[AntleredRuin]

See, I wouldn't have thought so either about the cables, but this is weird!
I drove home (over an hour) and it drove great! Was able to floor it and it revved and shifted great. Did not smell like gas once either. I am seriously confused.
Does the throttle cable only directly control the air intake, or does it control gas flow as well? Maybe I was making the mixture extremely rich originally by not allowing enough air in?

 

[AntleredRuin]

Alright, while definitely better, it's still not perfect. The hard start when warm is drastically better (again not perfect). It's not stalled out on me at all when starting, but the RPMs have dipped to 'nonexistantl' for a second a couple of times.

It can definitely rev better, but still feels like it's starving for fuel sometimes. The RPMs rise, but the speedo stays the same. This only happens when floored (which I hardly ever do) so it's not really an issue. I'll rent a fuel pressure gauge soon and see what I can do.

My coworker won't let me borrow his MAF (which I really can't blame him for, in case SOMETHING happens to it; we both live over an hour away from the office in opposite directions), so I might just buy one. There are a few cheap ones on Amazon that I'm checking out. Mostly good reviews, with the negative ones saying that it ONLY lasted 2 years or so. Well, at a fifth of the price of OEM, I'm willing to try, and I'm not losing much if it doesn't help. I might even get a spare just in case if it does help (free shipping).

I'll keep updating this thread with my finds just for public knowledge.

 

[gamefreakgc]

Alright, while definitely better, it's still not perfect. The hard start when warm is drastically better (again not perfect). It's not stalled out on me at all when starting, but the RPMs have dipped to 'nonexistantl' for a second a couple of times.

It can definitely rev better, but still feels like it's starving for fuel sometimes. The RPMs rise, but the speedo stays the same. This only happens when floored (which I hardly ever do) so it's not really an issue. I'll rent a fuel pressure gauge soon and see what I can do.

My coworker won't let me borrow his MAF (which I really can't blame him for, in case SOMETHING happens to it; we both live over an hour away from the office in opposite directions), so I might just buy one. There are a few cheap ones on Amazon that I'm checking out. Mostly good reviews, with the negative ones saying that it ONLY lasted 2 years or so. Well, at a fifth of the price of OEM, I'm willing to try, and I'm not losing much if it doesn't help. I might even get a spare just in case if it does help (free shipping).

I'll keep updating this thread with my finds just for public knowledge.

Just for kicks, has your transmission ever acted weird before? Slow shifts, trouble shifting from Park, etc.? Fluid is good?

Also, to answer the cable question, the accelerator is 100% mechanical (or at least it is on my 98, 00-02 might be different) so it doesn't really matter a whole lot. It will respond a lot better but if the throttle plate is shut then little to no air is flowing, so the MAF isn't reading much air flow and cuts fuel. That's why I had mentioned it's not going to help the hard starts and RPM cut outs at high speed.

 

[AntleredRuin]

Just for kicks, has your transmission ever acted weird before? Slow shifts, trouble shifting from Park, etc.? Fluid is good?

Also, to answer the cable question, the accelerator is 100% mechanical (or at least it is on my 98, 00-02 might be different) so it doesn't really matter a whole lot. It will respond a lot better but if the throttle plate is shut then little to no air is flowing, so the MAF isn't reading much air flow and cuts fuel. That's why I had mentioned it's not going to help the hard starts and RPM cut outs at high speed.

It's never had any issues shifting, other than the downshifts which the tranny cable adjustment helped immensely. Fluid is looking a bit dark so I'm planning a 'slow flush' (not with a machine) this weekend.

I have a '99 so my accelerator cable should be the same as yours. Alright, that makes sense. Weird sensor I guess, then.
I'm also going to do a radiator flush this weekend, and while I'm at it, I'll pull the top timing cover and clean the camshaft sensor. Any tips on how to check if it's ok? The crankshaft sensor is down behind the water pump near the alternator, correct? I might try to access that as well and see how dirty it is. Same question about testing the sensor.

 

[jeremyc74]

Also, to answer the cable question, the accelerator is 100% mechanical (or at least it is on my 98, 00-02 might be different) so it doesn't really matter a whole lot. .

They're mechanical up until the '01 I believe. My '00 is still mechanical. :focus:

 

[Illicitdream]

Alright, while definitely better, it's still not perfect. The hard start when warm is drastically better (again not perfect). It's not stalled out on me at all when starting, but the RPMs have dipped to 'nonexistantl' for a second a couple of times.

It can definitely rev better, but still feels like it's starving for fuel sometimes. The RPMs rise, but the speedo stays the same. This only happens when floored (which I hardly ever do) so it's not really an issue. I'll rent a fuel pressure gauge soon and see what I can do.

My coworker won't let me borrow his MAF (which I really can't blame him for, in case SOMETHING happens to it; we both live over an hour away from the office in opposite directions), so I might just buy one. There are a few cheap ones on Amazon that I'm checking out. Mostly good reviews, with the negative ones saying that it ONLY lasted 2 years or so. Well, at a fifth of the price of OEM, I'm willing to try, and I'm not losing much if it doesn't help. I might even get a spare just in case if it does help (free shipping).

I'll keep updating this thread with my finds just for public knowledge.

Buy one for cheap off eBay like I stated before, but make sure it's a good reliable seller and they have a return policy... When you get it clean it with MAF cleaner and plug it in. I recommend restarting the ecu by unplugging the negative battery cable and pulling the EFI fuse...

 

[AntleredRuin]

Buy one for cheap off eBay like I stated before, but make sure it's a good reliable seller and they have a return policy... When you get it clean it with MAF cleaner and plug it in. I recommend restarting the ecu by unplugging the negative battery cable and pulling the EFI fuse...

I ordered a cheap MAF off Amazon (I trust their return policy better). It was the same model number as a few on eBay and about $5 - $10 cheaper depending on the seller. Even if it doesn't work and they won't accept returns for whatever reason, I'm *ok* eating $18 with free shipping. If it DOES work, then I'll buy a couple extra to keep in the glove box or something. At a 5th the cost of OEM, I'm OK if it breaks again in a few years.

I did an oil change and transmission slow 'flush' over the weekend. (pulled the pan, cleaned it and the filter out real good, topped it off, then fed new fluid through while draining the old fluid from the hose to the radiator. It shifted pretty smooth before, but this is great now.

I also order some Toyota Red NOT pre-diluted coolant with the new MAF sensor. They should be in tomorrow. I'll do the MAF sensor when I get it, but the coolant change will have to wait until next weekend. I'll remove the top timing cover and clean the Cam sensor while I'm at it. Never hurts.

 

[gamefreakgc]

Sounds like you have a good game plan. Let us know how it turns out after a few days of driving!