Troubleshooting 3rd Gen 3.4 Misfire Code

[imjustdad]

did this all start suddenly, like one day ? I find it hard that two injectors go bad as same time. Anything is possible

Hi 3bears, yes, it started all at once, in a single day. Hasn't gotten better, hasn't gotten worse. I seem to be able to recreate it at will, and whatever I do, the codes [301/304/300] continue to point at Cyl's 1 & 4.

I'm a big fan of probabilities, and I'm with you, I just don't think it's likely [although possible] that two injectors, different banks, went bad all at once, especially two that the cylinders share the same coil's voltage. Possible, but...

Getting ready to call a couple places and see if a good diagnostic machine locally can point me in the right direction. Half tempted to change the igniter, the thing that's just upstream of the 1/4 coil just to see...

 

[imjustdad]

If you have spark in one then check the #1 injector. (is easy to get to) it should be 13 to 13.6 ohms cold and higher like 16 ohms when hot. if the injectors are good then do a compression test to rule out the head gasket.

Yes, very true Spartacus. It may be a pain to swap 'em around, but I CAN get to the leads for a that injector. I'll try that.

I thought of head gasket, but since those two cyl's are on different sides of the motor I didn't think much more of it. At 330k, it's certainly possible though. Thanks man.

 

[spartacus]

Yes, very true Spartacus. It may be a pain to swap 'em around, but I CAN get to the leads for a that injector. I'll try that.

I thought of head gasket, but since those two cyl's are on different sides of the motor I didn't think much more of it. At 330k, it's certainly possible though. Thanks man.

I agree with your head gasket opinion. I am leaning bad injector.

 

[imjustdad]

OK, checked Cyl1 injector cold/"running fine" state and it was 13.6 ohms.

Checked it warm, after re-creating the misfire state, and it was 15 ohms -- close to Spartacus's values. No smoking gun there, unfortunately.

Called a local "Japanese import specialist" and apparently his diagnostic machine would no sooner point to anything beyond which cylinder(s) was missing than my $50 dongle... But insisted the reason plug wires didn't fix it was because they weren't OEM Toyota wires, that if I'd run down to the stealership and get me some, it'd be sunshine and roses. This is why I do 80% of the family fleet work myself...

Crap, my Porsche diagnostic'll show cam deviation angles and all manner of stuff. You'd think somebody could see into a Toyo misfire and tell if it's an injector, an igniter, or the bloody ECU letting the deal go down. More local shop calls tomorrow. Still open for suggestions if anyone has a flash of brilliance.

 

[DreadPirateJon]

I was having P0300, 301, 302, 303. And could not figure it out myself. Until I replaced the air filter prior to a trip. The filter looked ok, but had gotten completely full of mud in the folds.

For the 301 and 304, I still am suspicious of something in the ignition. Its not the coil, and wires are new. Have you looked at the plugs themselves? What about the pigtail going to the coil?

 

[DreadPirateJon]

OK, checked Cyl1 injector cold/"running fine" state and it was 13.6 ohms.

Checked it warm, after re-creating the misfire state, and it was 15 ohms -- close to Spartacus's values. No smoking gun there, unfortunately.

Called a local "Japanese import specialist" and apparently his diagnostic machine would no sooner point to anything beyond which cylinder(s) was missing than my $50 dongle... But insisted the reason plug wires didn't fix it was because they weren't OEM Toyota wires, that if I'd run down to the stealership and get me some, it'd be sunshine and roses. This is why I do 80% of the family fleet work myself...

Crap, my Porsche diagnostic'll show cam deviation angles and all manner of stuff. You'd think somebody could see into a Toyo misfire and tell if it's an injector, an igniter, or the bloody ECU letting the deal go down. More local shop calls tomorrow. Still open for suggestions if anyone has a flash of brilliance.

There are so more in depth data that is able to gathered from the DTCs called Mode 6. But I have not been able to work out a way to read it without a toyota dealership tool. The mode 6 may help as it will tell current conditions of the engine when the DTC set.

 

[imjustdad]

I was having P0300, 301, 302, 303. And could not figure it out myself. Until I replaced the air filter prior to a trip. The filter looked ok, but had gotten completely full of mud in the folds.

For the 301 and 304, I still am suspicious of something in the ignition. Its not the coil, and wires are new. Have you looked at the plugs themselves? What about the pigtail going to the coil?

Hey man. Thanks for the input. Yes, I changed the plugs in the two missing cylinders when I changed the wires -- leave nothing to chance right? They looked fine, not fouled or discolored, electrodes good...

The pigtail to the coil seems... fine. I didn't spend a lot of time with it, but wiring or insulation didn't seem brittle. Your question is a good prompt to throw a meter on it [I think it's only 2 wires] in the "I'm OK now" state and then again following the "make it miss" procedure. I'm guessing it's just a 12vdc pulsing per firing sequence from the igniter.

Re: the DTC's, yeah, it's like next-level kind of info. I still haven't given up on finding someone nearby that I can slide a few shekels to see if a good diagnostic machine can shed some light. Thanks for the help!

 

[Bad Luck]

Do a compression test before changing fuel injectors

 

[imjustdad]

Do a compression test before changing fuel injectors

I'd say that's a good idea, thanks.

 

[Jhall]

FWIW, I had a similar problem and it ended up being the MAF. I replaced that and everything cleared up. Like you, the coil pack and all the injectors checked out. It also isn't consuming any coolant. It's been running fine for months now with the new MAF.

 

[imjustdad]

FWIW, I had a similar problem and it ended up being the MAF. I replaced that and everything cleared up. Like you, the coil pack and all the injectors checked out. It also isn't consuming any coolant. It's been running fine for months now with the new MAF.

Thanks for the input J. Hadn't considered the MAF. Was yours throwing misfire codes on specific cylinders consistently?

 

[Jhall]

Thanks for the input J. Hadn't considered the MAF. Was yours throwing misfire codes on specific cylinders consistently?

I remember that it was throwing a cylinder 1 misfire, and I believe another (maybe 3 or 4), but to be honest I can't quite remember. Good luck!

 

[imjustdad]

Update: Local shop had it for over a week. They're stumped and giving up, and I'm picking it back up today. I'm going to throw a used but known-working igniter at it and see what happens.

If anyone has a flash of brilliance, I could use the illumination about now...

Again, drives fine when first started. Drive it a few miles, turn it off for 10-15 min's, restart, and it misses on Cyl's 1&4. This can be replicated with great consistency. Changed Coils, plugs, wires. Moved same around, miss stays with 1&4. What the heck?

Thx!

 

[spartacus]

Update: Local shop had it for over a week. They're stumped and giving up, and I'm picking it back up today. I'm going to throw a used but known-working igniter at it and see what happens.

If anyone has a flash of brilliance, I could use the illumination about now...

Again, drives fine when first started. Drive it a few miles, turn it off for 10-15 min's, restart, and it misses on Cyl's 1&4. This can be replicated with great consistency. Changed Coils, plugs, wires. Moved same around, miss stays with 1&4. What the heck?

Thx!

The only way to be sure is to play musical chairs and swap injectors 1 and 4 with other cylinders. If that checks out then I would look at valves, leaking vacuum passed the valves.

 

[Bad Luck]

Update: Local shop had it for over a week. They're stumped and giving up, and I'm picking it back up today. I'm going to throw a used but known-working igniter at it and see what happens.

If anyone has a flash of brilliance, I could use the illumination about now...

Again, drives fine when first started. Drive it a few miles, turn it off for 10-15 min's, restart, and it misses on Cyl's 1&4. This can be replicated with great consistency. Changed Coils, plugs, wires. Moved same around, miss stays with 1&4. What the heck?

Thx!

Did you have a compression test done yet?

 

[G_Raw]

If you are recieving a random misfire code in parallel with a #cylinder misfire the firing order is incorrect.

Not necessarrily true. If you get a cylinder misfire followed by a random misfire code then you'll likely get the coinciding coil cylinder shortly after. So po303 followed by po300 will likely result in a po306 code. This is due to the ecu trying to account for the issue and make the engine run as smooth as possible despite there being a problem. Since cylinder 6 and. Are both ignited by cylinder 3 coil that is the likely series of code.

 

[imjustdad]

Did you have a compression test done yet?

Not yet, Bad Luck, but it's probably coming. At this point I'm still looking for a single point of failure whereas those cyl's are on separate banks. My plan at this point is to:
1. Change the igniter
2. Swap injectors around and see if miss follows
3. Then look at compression and ECU, wiring.

A bad output from the leg of the igniter that feeds that cyl1/4 coil would do it. Fingers crossed. Thanks for all the input gentlemen.

d

 

[Bad Luck]

Not yet, Bad Luck, but it's probably coming. At this point I'm still looking for a single point of failure whereas those cyl's are on separate banks. My plan at this point is to:
1. Change the igniter
2. Swap injectors around and see if miss follows
3. Then look at compression and ECU, wiring.

A bad output from the leg of the igniter that feeds that cyl1/4 coil would do it. Fingers crossed. Thanks for all the input gentlemen.

d

I would check compression before doing anything else. It's the best way to determine if you have a mechanical or electrical problem.

 

[imjustdad]

Gentlemen, my apologies for not posting back sooner. I'm ecstatic to report this has been solved. To be brief, it was the Cyl 4 injector that was bad. I swapped injectors around, and the misfire followed that injector. I replaced it, and it runs fine now.

The tandem codes the system was throwing -- the two electrically-related 1&4 cylinders -- was, after all, just a red herring. I suspect the ECU was trying somehow to compensate for no fuel at Cyl 4, and it affected Cyl 1 in the process. In reality there NEVER WAS anything wrong with Cyl 1, it was just that lyin' SOB of a computer SAYING there was.

Hope this helps some poor soul out there save some time running this around the block multiple times. Thanks all for the input and God bless!