Toyota misfire under load codes

Gene from Glendora Owner Posted   Latest   Edited  
Discussion
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2005 Toyota 4Runner Limited 4.7L (2UZFE) 5-spd (A750F)
P0305 - Cylinder 5 Misfire Detected
P0308 - Cylinder 8 Misfire Detected

Hello everyone, we have this vehicle that sets this code under heavy acceleration like getting on the freeway. The check engine light will start flashing and it will set the codes, but the misfire is never felt. The compression on all cylinders is even across all cylinders 150 psi, regular maintenance like spark plugs fuel injection service and even the replacement of two coils. Has anyone experiences something similar?

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Michal from Houston

 

Owner
 

PLugged cat? intake vacuum must be higher at 2000 rpm than idle. Poor injector delivery? Many possibles here, need more testing. 

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Chris from Commack

 

Diagnostician
 

Hello Gene, what are the fuel trim numbers at idle, at load? Are these the only codes in the vehicle? How about the misfire counters in mode 6?

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Michael from Shelton

 

Technician
 

Have you performed a VE test?

This test should point you in the direction of the cause.

+2

Matthew from Smyrna

 

Owner/Technician
 

Not trying to throw a silver bullet out there but check the torque on the A/C compressor bolts. Had a 4.7 take me down a dark road with a similar issue, runs fine at idle, no noticeable misfire, VE and fuel trims well within spec. Turns out engine had been replaced and the AC compressor was slightly loose causing a vibration that was picked up as a misfire under load.

+4

Gene from Glendora

 

Owner
 

we've had the injectors flow tested and the turn back good. the ve checks good fuel trims are normal definitely not lean under accel. 7 counts of misfire on both of the cylinder from mode 6, its seeing a misfire but its not definitely felt. just recently it set a p1445 for air injection bank 2. But i cant connect why 2 cylinders in different backs misfiring. I have seen postings for bad valve springs maybe a valve fluttering under load. 

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Chris from Commack

 

Diagnostician
 

can you recreate the misfire counts by power braking?

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Gene from Glendora

 

Owner
 

no misfire counts power braking it at all.

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Michael from Shelton

 

Technician
 

If your suspecting valves fluttering you should see it with a vacuum gauge. It's been a while since I had one but had a few mid 90 Chevrolet pickups I had to find it with a vacuum gauge on the windshield.

I messaged a buddy on this one who works for a dealership. Waiting for his response for anything common he has seen. 

Those 2 cylinders are side by side and number 6 is in between the firing order of I'm correct.

Just for sake of question have you looked at cylinder 6 for any issues? 

The misfire monitors do report misleading information at times. Just a thought. Worth a look. 

+1

Chris from Commack

 

Diagnostician
 

Good thought Michael.

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Martin from Burleson

 

Diagnostician
 

Were the two coils on the same cylinders that are coding for misfires now? Were they oem coils? I've have had aftermarket coils bite me before. It had to do with the IGT or IGF circuits. I think all the coils share one of those circuits. I don't have a diagram in front of me right now so excuse me if I'm incorrect. It may be worth a look. Hope this helps. 

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Michael from Shelton

 

Technician
 

Yes I remember getting bit by a AF coil on a tundra but it was felt when misfiring.

Martin I just looked at the wiring diagram and they do share the same circuit. 

As well as 8 and 2.

IGF2. PIN 25 at the PCM. RED/White. 3,5,8,2.

Pin 24 is IGF1, RED/Yellow. Is coils 1,4,6,7.

Would be worth scoping. Both circuits during the event. 

+1

Michael from Shelton

 

Technician
 

AF. Sorry After Market coil. 

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Martin from Burleson

 

Diagnostician
 

Early on in my career it happened to me in a 6 cylinder van. I believe the misfire was not felt either. It actually had codes for every cylinder. They all shared the igf circuit. It had returned after we repaired a misfire( bad coil) and replaced plugs. It was an am coil. I was very new to scoping things but I decided to scope the igf circuit. With an injector scoped for a cylinder ID. I didn't really know what I was looking at but there was one cylinder that was different and it was the cylinder with the aftermarket coil. New oem coil solved my problem. I'd be interested to see a capture. 

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Don from Monrovia

 

Technician
 

Look at your short and long term fuel trims for each bank and the rear 02 sensors to determine if it's fuel or ignition related. 

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Gene from Glendora

 

Owner
 

hey Don the fuel trims just show fuel being added for a few seconds and then they just level out as soon as you back off the throttle. It would only add to +15% and then back to like 6 or 9%. The customer pick the vehicle up at this time. He will bring it back and he has more time to spare it.

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