AEB misfiring before and after R8 coilpack install

[paulpas]

Hello,

I've had a history of misfires on my 1999 A4 Quattro Avant 5MT.

First off, I have had misfires before and after my stroker+gt2871r install. Before the upgrades I had the ICM replaced and it was good, but never perfect (probably due to low compression causing oil blow-by to slowly coat the plugs). The same 630cc injectors are in use before and after the engine swap.

Now I have a new stroker motor and GT2871r with 630cc injectors from the last engine. VR6 MAF. I only get misfires at WOT, or near WOT, when I am full on boost, lets say 4800-7000 RPM. It's sometimes 1 cyl, sometimes anywhere up to all 4. I can get to 7k limit under partial on-boost acceleration.

I've done the ICM delete with r8 coil packs, no change.

I've run a ground wire from the battery to the coilpacks on the valve cover. No change.

Plugs are new and gapped to .040, per 034's kit suggestion. Otherwise the car runs fine. After I ran the ground wire the idle stabilized a little, voltage reported from the ECU went from 13.2-13.6v to 13.6-14.1v.

Any suggestions?

[StriktlyAudi333]

Sounds like you're either starving for air or fuel. Swap out the fuel filter? Kinda sounds dumb but it could be causing a restriction?


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[paulpas]

I have a new fuel filter with the high pressure fuel pump. Some more information is that now when it misfires I can let off the throttle and it will continue to misfire for about 30 seconds until I do a 20% throttle acceleration until it clears up. It's almost like some capacitors lose their charge and I need some time to regroup. That doesn't match what I see with my voltage so that might be a red herring.

[paulpas]

Update:

I was idling the car with the front passenger door open. Hearing the fuel pump whine, that was fine, but when the idle was misfiring (is that what it is doing at idle?) I also heard the fuel pump cut out for that split second. Maybe the ignition isn't the problem, but I lack the comprehensive troubleshooting experience to narrow it down with intelligence. The only CELs I get are P0300, P0301, P0302, P0303, and P0304. Again, at or near WOT only on approx full boost.

It's also noteworthy that I accelerated quickly from a stoplight and the car started misfiring. I let off the gas pedal and it kept misfiring on cyl 1 and 4 for 30 seconds (new development for it to last for so long) and I was cruising at 45mph in 5th thinking it would clear up, and it didn't. It kept misfiring at the stop sign at idle, and then it cleared up once I did a 20% throttle acceleration in 5th until some boost kicked in (5-10psi), then things smoothed out.

[NY337]

Sounds like your getting consumed too much in the problem. I do it ALL the time! Get back to basics. Who tuned the car? Is it possible to send them logs of 3rd gear pulls? Also, invest in a cheap fuel pressure gauge. It doesn't have to be dash mounted or anything just stick it through the cowl while you are driving. Measure the fuel pressure at idle, when running, and at WOT. I am not sure what the factory fuel pressure (FP) should be, but if you are hearing the pump cut out then the pressure will drop considerably. It could be something as simple as a bad ground to the pump, a bad pump, or worst case, a bad tune.

I agree that you are starving for air and/or fuel rather than iginition. I am experiencing a misfire also that is not the ignition. I just changed injectors, but I didn't change the injector cups. I have a feeling I could be leaking boost through the cyl. 4 inj. cup causing the misfire I am having. My misfire is only in the 4th cylinder. I swapped coils with cyl. 3 and the problem did not follow, so I know its not ignition related.

[Dillon Clark]

Hmm, I just replaced my coil packs from ESC tuning for my cylinder 4 misfire code. It made it run a little better, but still gets the misfire........I better check my air/fuel also!

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[vrmm]

.40 is huge. I'm sure there are people out there that run it and are fine, but I have to be at .024 to get rid of misfires up to like you speak of. You should try .028. Nothing bad will happen if you do.

I was using .028 on stock coils and switched to r8 coils. No change. Once I jumped my gap to .024 haven't had another issue. You could try lowering your boost to like 5psi if you can and see if it happens. If it does not misfire, then lower your gap and turn it up.

[Dillon Clark]

Turns out, my crankshaft position sensor would start to fail once it got hot and would cause my misfire.......just ordered a new one on ECS Tuning.

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