All Things Mk5 > How to Guides / Troubleshooting

Lumpy Idle issue

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ChazGTI:
Been trying to diagnose this for a few months. Spoken to a few other people with the same problem.
She idles like this (no rev change) when cold and warm. I hadn't changed anything recently when I first noticed it. Goes away after revs rise past 1k and engine performs well across all gears etc. She does sometimes tend to be hesitant at low revs when cold, not sure if that's related.

Timing Belt, tensioners and water pump done 15k ago, just done cam chain and tensioner, Dev D Diverter Valve with GB DV+, Newish plugs and coils (all), Stage 1 map. Checked PCV and its solid, replaced gasket anyway. No codes on VCDS and no misfires.
Only thing the car really needs is fuel filter replacement, could that be it?
Want to get it sorted as it just doesn't sound healthy, although like I said, there's no problems after my foot is down.

Ricky123:
Injector/s? Check them using vcds

Excessive carbon build up? Only one way to find out really..

Maf? Unplug it and see if there's any change

pudding:
It does kind of sound like injectors.  The fuel pressure increases a lot when you put your foot down, so partial nozzle clogging isn't as noticeable there as it is at idle.  The misfire counter isn't great at idle speeds, so can take ages to register a fault.

I do my fuel filter every year.  Mainly because it's got a pressure regulator built in and when it gets weak, it can cause cold starting issues.

r5gtt:
Check your hpfp cam follower as this is a common cause for this sort of behaviour especially when it's about had its life span and worn down to its limit.

whitemoredooor:
Could be DMF is begining to fail.

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