About 2 months ago I started to have a slight misfire occurring @ 6000 rpms and up. It was very inconsistent, however it did it especially while on the track. In my search to find the cause, I found that both my battery posts were loose, I re-tightened them and it seemed to clear out. It started again within a week and the battery posts & terminals seemed tight. we swapped in another set of plug wires to rule that out(I'm still using the stock ones @ 27000 miles) and didn't notice any change, we checked the plugs and tried re-gapping them down from .27 to .23 and the problem cleared right up. I then added a Sun Pro ignition module to help boost the spark (seems like a band aid approach)re-gapped my plugs back to .27 and everything was good for awhile, then the misfire returned at my next track event a week later. I just recently replaced the battery and everything's been fine, then today it returned with a vengeance. It only does it @ WOT @ about 5800-6000 rpms, but not every time. I'm tending to think it's a grounding issue. I'll take off & clean my terminals tomorrow and see if that helps. I'm currently running NGK BPR7ES plugs gapped @ .23 which seems really small.
Any advice would be greatly appreciated!

 

What mods do you have? Do you have a big turbo?

If you have money to burn, you could always try the Okada Plasma Coils that TTP Engineering is selling... they are new coils with built-in amps. They also work well with the Sun Auto module you have already.

 

He's running an EvoGreen I think.

 

Mods: FP Green turbo, 880 injectors, Walbro 255 FP, AEM EMS, BR intake w/Tiall 44mm BOV, BC 280i/272e set straight up, 2"to 2.5"LICP, Evil eBay FMIC 31x 12x3 w/3" inlt/outlet, MR o2 & headers, Tanabe 2.75" DP, 3.5" exhaust w/ 4.5" straight thru muffler, Sun Pro ignition booster?, Carbonetics twinn carbon clutch, Sgt Blamo's ugly AHASD, ROBISPEC custom suspension set up w/KW Clubsports, minor brake upgrades, etc.

Sparky,
How ya been? I just dynoed it two days ago on a Dynojet, made 397.8 WHP on 93 oct @ 22psi. I will be posting the dynographs later today or tomorrow.

 

I checked both my battery connections and then road tested it again, same thing, misfire occurs @ about 5800-6200 rpms in 2nd & 3rd gear. AFR's are around 11.6-11.8. I checked my plugs, they looked fine, they were gapped @ .23. I decided to throw in a set of Autolite Iridiums gapped to .27 from .43, still misfired, maybe a little worse.
Anyone have any idea what may be causing it? I tend to think it's a ground related issue, but I'm not sure. Any advice would be great!

 

Anyone?

 

Bump for advice

 

There has been some discussion on this in other forums. Several of us are getting a strange missfire/backfire...aka sputtering and loss of power when you get on the gas fast. If you lay into is slowly all is good.

Here is what I have been doing to eliminate the problem.

1) Check for boost leaks
2) Check for vacuum leaks
3) Check for leaks at the injectors
4) Check the throttle body seals (not the gaskets) for leaks (mine leak at only 5psi)
5) Make sure all of the grounding locations are corrosion free and tight
6) Check plugs (Duh...I know)
7) Check plug wires and all wireing to the coil packs
8) Ensure you injectors are scaled properly
9) Calibrate your MAF (if you have one) to match the flow of hard intakes

I have done all of this and the probelm has beet getting less and less of an issue.

My major problem is that my car has sat for over a year while i was deployed.

If you find anything else....please post up. This is a very frustrating issue.

Paul

 

what code does the ecu give you? is it p0300?
check the connections of your egr valve and all its vaccum lines.
maybe you will need to upgrade your ignition system

 

The car has an AEM EMS so no codes. I recently had new injectors installed with the FP Green turbo. Strange thing is, it was just fine when on the dyno a few days ago, the injectors where @ 80% @ WOT while on the dyno. It only does it at about 5800-6000 rpms & up, but not every single time, more like 3 out of 4 times.

 

I have had similar problems drag racing at high boost on racegas. On the street I havent had an issue, but my current theory is that its blowing out spark. Whether I have weak coils or a weak coil I am not 100% sure but I am going to be remedying that. I have logs where the misfire is very evident in with the rpm not picking up and it doesnt even show knock.

There are a few reasons I think its doing it in addition, but without proof I am hesitant to say. When I get a chance to do some testing I will see what I come up with and maybe be of some help.

 

Have you datalogged it when it sputters to check AFR's and Knock, etc?

 

It sounds like you are at a point to up grade to a COP set-up like the AMS or buschur set-up. I am right there with you. I had a 6K and up miss. I have went to BPR8ES and it is much better than brand new stock plugs. I gapped mine at .022 and the miss is gone for the most part. Some times in higher gears 4 5 above 6K the boost flutters just a bit but not a complete miss.

 

I'm going to try to check all my grounds. The COP set up seems a tad expensive @ $1100 ! Ouch. I sure hope I can correct the problem for a fraction of that cost.

 

In my case the AFR's bounced in relation to the RPM dropping and not firing, but there was no knock. Most of the time this was happening was when it was really loaded up at high boost (30psi) on C16. I have a COP setup that I will be switching to because even at .019 it was doing it. It was much worse when it was at stock gap of .026.