Rough idle.

[Lee1976pr]

Hi guys.
I have a 2008 S3 and the idle revs fluctuate up and down. I have changed the pcv, carbon tank and the n80 valve but it still hasn’t made a bit of difference. Any ideas guys?

 

[samuelh_888]

Vacuum lead - is it possible to get it smoke tested?

 

[Garrett 69]

Cold engine, warm engine, or both?

 

[Lee1976pr]

More often when it gets warm.

 

[Garrett 69]

Could be the MAF sensor or a leak in the air intake system.

 

[Genespleen]

N80 valve actuator (the magnet) can also get sticky, but you likely saw that when replacing the valve itself.

 

[Lee1976pr]

I have now changed the MAF and the DV. It seems to run a little bit better but on cold starts it’s running like a bag of nails until it warms up. Any ideas?

 

[Lee1976pr]

Also I found that the oil filler cap was in a bad way. Not sealing properly. I’ve replaced that and the fluctuating revs at temperature have corrected. It’s just the rough cold starts now to sort out. I have found a small blow from the exhaust at the centre flexi pipe. So time to repair that and a set of coil packs and plugs and see how it goes. Fingers crossed it works. My wife is teasing me now about her perfect mk1 TT with 200k miles on it and just passed another mot with no advisories at all.

 

[Lee1976pr]

So. I have now also changed the coil packs and plugs and it is still misfiring. Any ideas guys?

 

[Garrett 69]

So it's now only misfiring when cold? Sounds like it could be the cold start/auto choke system, assuming the S3 has one? It's a long time since I had a petrol engine car that gave me trouble.

 

[Lee1976pr]

So it's now only misfiring when cold? Sounds like it could be the cold start/auto choke system, assuming the S3 has one? It's a long time since I had a petrol engine car that gave me trouble.

Only misfires for a few seconds on start up when cold but misses at 2500 - 3000 rpm now.

 

[ch1z64]

If u happen to have the old style dip stick ( orange one ) replace that as they where known to cause issues due to the 'o' not sealing correctly when pushed bk in and the rubber parts inside degrade quickly . That itself can give idle issues

Sent from my SM-G970F using Tapatalk

 

[Lee1976pr]

So. I have now changed N80 valve, pcv, DV, carbon tank, all pipes connected to them all, coil packs, plugs, maf sensor and it is still misfiring. Time for the injectors now I think. This is really starting to get me down.

 

[Genespleen]

I've had a rough idle and misfire on a couple of occasions that was cured by removing the camshaft actuator magnet and (1) freeing up the actual actuator--which had gotten stuck; and (2) freeing up the magnet pin, which had also gotten sticky. Here's a video that may be helpful: VW Audi 1.4 1.8 2.0 TSI P0011 Camshaft code diagnosis and repair

 

[xaudi]

What fault code? You have to diagnose the problem first. You can't just go and replace parts without knowing the culprit.

 

[Lee1976pr]

The codes are PO300 PO301 PO304 PO171. I have replaced all the parts so far as preventative maintenance as they are all parts that commonly fail.