Maddening misfire issue between 3200 and 4200 RPM

[shanewendel]

Would this slight seepage indicate anything?

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[11GT50]

The bulb is the transmission vent.

 

[shanewendel]

Here's a Forscan Log from a drive to go get some wings with my son if anyone cares to look. 48 misfires in about 15 minutes of driving , most of those being on Cylinder 7 when I was in the offending RPM range getting onto the highway.

I messed with every electrical connector I could reach today, hoping to find a loose one. I bought a leak down tester to do that tomorrow. I will likely also pull the intake manifold and check the IMRC flaps and swap the cylinder 7 injector with another cylinder.

 

[Tank]

You have a bit different circumstance than I do but are you able to log fuel pressure by chance? I have a P0300 as well but it came with a P0192 and no other misfire code. I get intermittent loss of fuel pressure - down to 0 then returns to normal - under load. I don't think our issues are related but I'm still curious.

See the last two posts in the GT 350 Basics sticky for info and tests on your P0192 DTC.

 

[DCShelby]

Could also be a bad coil on that cylinder. Audi used to have issues with bad coil packs doing the same thing. I’d also switch the coil packs around. Take number 7 out and check the impedance, it may have a crack in the housing or bad innards.

 

[shanewendel]

Could also be a bad coil on that cylinder. Audi used to have issues with bad coil packs doing the same thing. I’d also switch the coil packs around. Take number 7 out and check the impedance, it may have a crack in the housing or bad innards.

Thanks but see first post, already did that.

 

[Cobra Jet]

Here’s the location to the EVAP on the 5.2:

 

[shanewendel]

Are we supposed to have the foam covers over the fuel rails like the 5.0? If so, mine are missing.

 

[Cobra Jet]

EVAP Purge Valve location:

 

[honeybadger]

Have you swapped injectors and coils to different cylinders yet?

 

[shanewendel]

Have you swapped injectors and coils to different cylinders yet?

Not yet, watching the A&M game!

 

[shanewendel]

More tests:

• Swapped the Cylinder 8 and Cylinder 7 injector, no change, still Cylinder 7 causing most of the misfires that are logged
• Tried running with the Evap Purge Solenoid disconnected, no change
• Tried running with the Evap Purge tube disconnected, no change
• Seems to get worse as the car warms up

Did a couple more stationary pulls - The "danger zone" range is actually more like 3400 - 4400 (at least today - only other change is that I took the strut bar off) I was wrong, you can feel it stumble when the misfires are logged. More so in the 3400-3600 range, can't really feel them in the 4000-4400 range, even though they are being logged at a higher rate.

Seriously though, I think could hold throttle at 3000 RPMs all day and I don't think a single misfire will be logged. Same thing for 4500+

This has _got_ to be some electronic/resonance/vibration/sensor bullshit, right?

Next thing I'm going to try tomorrow is unplugging the rear O2s, then I'll move on to the leakdown to rule out anything in the base engine. The only other thing I can think of is broken IMRC.

That's about all I can do from the test document that Tank posted, the rest of the stuff requires professional diagnostic equipment that I don't have. I guess it will be in the hands of a dealership at that point.

 

[Lurker_350]

Not yet, watching the A&M game!

Turned out better than I was expecting!

 

[shanewendel]

Have you swapped injectors and coils to different cylinders yet?

Can I just unplug the IMRC solenoids to check for IMRC issues? Not sure which way they default or if they are designed the same way as the 5.0.

 

[Tank]

You might want to hold off an further ‘stationary pulls’. High revs w no load is not good for the 5.2

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