CJackel492

I'm having issues with my V8.

Now and then the engine is rough at idle (more noticeable while in gear) and now and then it will get really bad and the engine light starts flashing for about 30 seconds and then comes on permanently and the misfire reduces. (I can stop it flashing the engine light if I increase the revs while it's having a fit).

I've recently had the timing chains done but the misfiring was happening even before they were done.

The codes that come back are random multiple misfires, usually on the odd cylinder numbers.

I've tried changing the coil packs but this hasn't done anything to help.

It's also had new spark plugs too.

Its really starting to bug me, because apart from the rough running, as engine power is also affected, some days she really wants to go but most days she's so lethargic and I'm sure economy is also affected (15 MPG can't be normal).

Carl,

mkv

I'm not well versed on these 4.2 V8 engines at all, but I've generally found that if plugs and coil packs aren't the issue, then the crank and/or cam position sensors are to blame. Perhaps do some more directed forum searching to see if these can be troublesome on your engine, and how easy and costly they are to replace.

CJackel492

If it was cam or crank sensor, surely I'd get a code?

Carl,

mkv

Not necessarily, I've seen a number of cars with misfires due to bad crank sensors not throwing a code. examples that I've personally changed sensors on are a few Mk4 and Mk5 Golfs. Might be a 4 potter but the electronics and sensor logics are basically the same. If the sensor is giving a poor timing reading, how would the ECU know... Until it gets so erratic that it's obvious I guess.

akingzkid

Carl,
I'm also having misfires but with no codes. Did you solve this yet and if so, what was it? My guess is you are still dealing with it, like me.