Intermittent Misfire Problem

[powerhearse]

Hey guys, newbie here! Sorry my first post is with a problem...I've search functioned this problem on here and haven't been able to find any new solutions as yet...

So here's the story. Since I bought my Stag ( C34 S2 RWD Auto) it's been having an intermittent misfire problem; the first I noticed was that on startup the Check Engine, TCS Off and Slip lights were all coming on. There was also a vibration I could feel through the steering wheel, felt like a slight misfire.

When I first bought it the guys from Redline told me it had been having this problem, but that they had replaced coil packs and plugs and it hadn't happened since. Well, it was still happening.

Since then I've taken it back several times, had the O2 sensor and AFM changed and a wiring loom problem fixed. The problem is less regular now but still happening, and if anything it feels like the misfire is getting worse (vibrations through the whole car now getting worse).

The misfire seems to go away after about 15 minutes of driving, but the TCS and Slip lights stay on (I assume this is because the ECU hasn't reset yet). At first I thought it was only happening when the engine was relatively cold, but a couple times now it's started missing halfway through a 30min drive.

When the miss is bad I can stand outside the car when it's idling and hear a popping from the exhaust. Driving-wise, when above about 2500rpm the problem seems to go away but there's a definite reduction in power. At idle through to about 1500rpm seems to be the worst, and it seems to resonate badly at a throttle position just above neutral throttle (exhaust resonating I think, as it vibrates through the rear of the car).

When throttle is applied in neutral, the problem isn't as bad as when driving. The vibration only really occurs at idle when it's in neutral.

I'm taking it back in again tomorrow to get the ECU checked out, but any ideas would be appreciated.

TL;DR version:

C34 RWD Auto: Intermittent misfire + check engine lights. Coil packs, plugs, O2 sensor and AFM replaced, wiring loom problem fixed. Still happening.

Edited July 28, 2013 by powerhearse

[Scriblez]

Sounds like your Coil Packs might be giving way man. I'd suggest getting a set of Splitfire Coilpacks fitted. Best money I ever spent.

Was having the same issue until I fitted them.

Good Luck!

[powerhearse]

The coil packs in it are brand new, replaced to try to solve this problem. Don't think they're Splitfires though, I might put a set of those in anyway

Edited July 28, 2013 by powerhearse

[stock stagea]

Are they brand new or what they had in the garge/workshop. I had the same problem less the light on dash replaced with 2 sets of coil packs from this mechanic, cracked the shits went and bought splitfires and has never happened again in 7 months.

[Scriblez]

I had the same issue man, tried using a couple of different sets of stock coilpacks and the problem persisted. As soon as I upgraded to the Splitfire system, there were no more issues at all.

[4bidn1]

Yeah sounds like could be cool packs , but check engine light should not be on . When you take it to them ask them what fault codes Ecu is throwing up and get them to reset .

I've run both splitfires and yellow jackets both are good coil packs

[wolverine]

I had the engine check light intermittently when the coils were on the way out. When plugged into consult it was throwing up a CAS fault but new coils (splitfires) sorted it out.

[Scriblez]

Same here, Check engine light came on intermittently when the packs were failing.

New set in, no issues at all.

[C34S2STAG]

Spitfires all the way. On our na r34 it had yellow jackets for only a few months until they failed. Like they say you get what you pay for!