Weird issue with RPMs - Help Needed!

[Danthefourwheeler]

So I've got a 2006 MK5 GTI manual 112k on the clock. Started having a weird issue where the revs would start rising randomly when in neutral or at a stop. Took it to VW to get full diagnostics done and they said the MAF (Mass Air Flow Sensor) was faulty. I took the car back, replaced the sensor and put a new PCV in for good measure. The issue stopped and the car seemed to run fine until...

Now that issue has gone, I've noticed something else instead. It's hard to explain but it only starts after about 20-30 mins of driving. What happens is, after accelerating and then releasing the throttle, the car seems to sort of carry on itself for a while, and I see the revs hover for a second or two, then all of a sudden it jerks into engine breaking and it starts to decelerate. Happens in all gears, at any speed, always the same effect. Accelerating like normal, come off the throttle, it continues to accelerate/maintain revs for a bit, then jerks and starts slowing down with engine breaking.

I've been reading around and heard it could be a boost leak or something similar, I've just ordered some new breather pipes that connect to PCV just in case once of them is torn or something.

Is there anything else I should be looking at?

Any suggestions are much appreciated

Dan

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[mjmallia]

Sounds like a vacuum leak.....boost leaks would take power away

[Danthefourwheeler]

Sounds like a vacuum leak.....boost leaks would take power away

What's the fix?

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[GVK]

Check for leaks on the servo pipes and the inlet, was your pcv aftermarket or genuine? As the non-gen ones can give as many problems as a knackered one!

[Danthefourwheeler]

Check for leaks on the servo pipes and the inlet, was your pcv aftermarket or genuine? As the non-gen ones can give as many problems as a knackered one!

It was genuine PCV, I'll check those other pipes, some people are mentioning the vaccum pump itself, or gasket?

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[GVK]

Spray some WD40 around the pipes/inlet if there is a leak the spray will cause the engine note to change.

[Danthefourwheeler]

Spray someWD40 around the pipes/inlet if there is a leak the spray will cause the engine note to change.

Ok thanks will give it a try

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