Rough idle when warm

[J66hhr]

Hi, 
My revs is jumping slightly on idle once the car is warm roughly about 100rpm. It smoothens/levels out if i turn on the air-conditioning or slightly hold the accelerater pedal to increase the revs.

It has happened after a stage 2 map with dsg and downpipe install from sa-tuning however they have assured me that they only tweak above 30% and not the idle

To eliminate the tuning from being the culprit they have put the car to stock and it did not make a difference. 

I have had it smoke tested, replaced all coil packs checked the dv, checked boost pipes, deleted PCV, replaced dipstick even put the stock exhaust on and still did not make any difference.

I have checked fault codes and i am getting 2 intermittent faults p0100 + p0299.

Someone here may have experienced something similar? I have had independant technicions have a look including a vw master technicion and still no faults found

[J66hhr]

Faults

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[muff1991]

i think you may have your answer there.. MAF sensor

boost not reaching target, is usually down to a boost leak, but if you have done all the tests and replaced the common parts, then this could be down to either:
The turbo actuator or the waste gate not sealing correctly if its broken
The N75 valve. (electronic actuator solenoid)
or at worst.. the turbo itself.

BUT before all that.. the P0299 could also be thrown up if the MAF is faulty.. because if everything else is not running correctly and targets are not being met, then this could be the cause.

[J66hhr]

i think you may have your answer there.. MAF sensor

boost not reaching target, is usually down to a boost leak, but if you have done all the tests and replaced the common parts, then this could be down to either:
The turbo actuator or the waste gate not sealing correctly if its broken
The N75 valve. (electronic actuator solenoid)
or at worst.. the turbo itself.

BUT before all that.. the P0299 could also be thrown up if the MAF is faulty.. because if everything else is not running correctly and targets are not being met, then this could be the cause.

Ive replaced the n75... any ideas if unplugging the maf sensor would be a correct method to test and eliminate it?

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[J66hhr]

Unplugged the maf sensor with the engine running and the pulsing idle became steady.. sensor back on and so is the pulsing..

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[muff1991]

Yep, that’s a pretty sure sign the MAF is buggered. Get yourself a new MAF and a genuine one too.


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[J66hhr]

Tried 2 different maf sensors same issue... seems a furthur problem must be causing both fault codes 

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[MIJ_JAGGER]

Air leak somewhere most likely seeing as idle is fine when you disconnect the MAF sensor

I’d start with putting the PCV back on, check it’s in good nick beforehand

[J66hhr]

Thats what i thought it could be at first faulty pcv easy enough to just block it off so thats illiminated.. flooded the vacume hoses and intake manfiold with brake cleaner still nothing to guide me towards a vacume leak

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