Rough idle

[fahim4094]

HI guys

I’ve got a edition 30 dsg with 118k on the clock. Recently I’ve been experiencing rough idle with my gti (stage2+ rtech)  - rpm not moving up or down - just feels jerky/lumpy in idle

Ive changed:

-pcv valve
-Cam follower
-Oil service/ sump clean - new pick up pipe - oil filter (quantum 5w-40) always used never given any problems before
-Ngk spark plugs
-R8 coil packs
-Main thermostat
-Fuel filter
Running Tesco momentum

But still facing rough idle. - any idea what could be the cause of this

[colesey]

Is likely the injectors needing cleaning. Try running a tin of Bg44k through to see if things improve.

[titchy]

my rough idle was caused by vac leak from coolant vac pipe below inlet manifold

[fahim4094]

I’ve scanned the car, these are the errors that are coming up

P0300-  Random/multiple cylinder misfire detected

P0303 - Cylinders 3 misfire detected

P1602 - power supply terminal 30 voltage too low

I’ve reset the codes, drove it around, errors have not come back, but still jerky/lumpy idle

[Dude2016]

I would guess could it be coil pack cylinder 3

[fahim4094]

HI @Dude2016

I've already replaced all 4 coil packs

[Dan_FR]

Errors take time/many occurrences to reappear depending on their nature

Firstly unplug the MAF and see if it improves. If it does you likely have some form of air/vacuum leak

If that doesn't help, then you probably have a dead/dying injector. Use VCDS to log the misfires at idle and tell us how many you are getting per minute on each cylinder

[pudding]

Injectors. Common problem.  Mine needed replacing at 80K.  Always at idle on the lowest duty cycle.  Usually smoothes out at higher rail pressures as it overcomes the blockage/lazy pintle.

[TechyTom]

HI @Dude2016

I've already replaced all 4 coil packs

Have you replaced the plugs too?

[J4k3]

Injectors. Common problem.  Mine needed replacing at 80K.  Always at idle on the lowest duty cycle.  Usually smoothes out at higher rail pressures as it overcomes the blockage/lazy pintle.

Exactly this, I’m experiencing a misfire on idle at the moment but disappears when running, I’m in on Friday at r-tech for injector cleaning/replace if necessary! I’ve changed coils, plugs, etc, so injectors are the last thing to be done to hopefully cure the problem! My cars on 59k also! 

[fahim4094]

@TechyTom As soon as I had experienced the rough idling, I booked it in the next day to have all the above replaced, so yes, I have replaced the spark plugs.

@Pudding I believe it could also be injector related problems - having the front end stripped hopefully after new years.

@colesey thanks for the suggestion, I need to try this I've heard a lot of good reviews about this.

It's really annoying, I start the car in the morning (Cold Start) struggles to turn over (sometimes) and starts to jerk in idle and feels like it wants to cut out, it is also very rattly from the front almost seems as the chain wants to snap -  but after I let it warm up for about 2-3mins - it seems normal with a little jerkiness/lumpy idle - and the chain doesn't rattle like crazy - but you can hear it, it's not revving normal - car drives fine and still pulls very good with this problem. I managed to do a round trip of 130miles with wynns injector cleaner and Tesco 99 - but the hasn't helped.

I will keep you guys updated after the front has been stripped. 

[Ytee]

Useful thread... I have the same issue on my BWA at 80k, although it sounds like yours is worse.

It's been doing it since I got the car at 70k but it's not got any better/worse since then and no VCDS codes either. Like you, I replaced the sparks, coils and PCV valve thinking it was one of those. It wasn't.

I have put a couple of bottles of Redex through it during that time, hasn't made any difference, although it does seem a bit better on 97/98 than on 95, and it's always better after a good Italian tune-up :)

I'll try the BG44K as suggested by colesey earlier. Failing that I'll be looking at changing injectors as well I guess.

Good luck with yours.

[fahim4094]

@Ytee When I bought the car a month ago, it was perfect - had a new turbo, stacks of receipt - drove it around for 2 weeks problem free - now problems are coming out left, right and center lool (GTI LIFE). Mine started off not that bad, now it's just getting worse.

I don't think Redex is that good. I was reading through injector cleaner reviews - someone did mention that Wynns Injector Cleaner helped with their car.

[titchy]

The best inj cleaner is Forte

[fahim4094]

@titchy would a vac Leak cause the car to struggle on start up - cold or warm