Car revving itself when coming out of gear! Help!

[Rawson]

Hi people.
My Ed 30 had been acting strange recently, it all started with the engine completely cutting out every now and then, it would always happen when I've been driving for an hour or so and the engine is hot. and when I've come out of gear/slowing down for a junction/lights. I would see the revs drop right down to zero then it would cut out. However it always starts immediately back up.

Now it is doing the same thing but even worse, when I come out of gear at a junction and I'm slowing down( foot only on brake pedal) the revs drops down and then back up -  revving by itself a few times before cutting out or going back to idling like normal.
The car is fine when it's idling, this is only happening once the engine is warmed up.
I have checked for boost leaks and can't find any.
I have changed the PCV to latest revision,
Checked DV perfectly fine no splits or cracks
I changed n75 valve with new pipe.
Fitted new MAF sensor after checking the wiring loom first for splits or craclaim
As I had code (P0100 G70 maf - supply voltage intermittent)  couldn't find any splits or cracks.
Fitted new maf and that code is gone now ( also my MPG has shot right up so I guess that maf was on its way out anyway)
But my problem still persists!
I have VCDS and have been logging, has anyone experienced anything like this before with there MK5?
Any ideas what more I can log?
Logged misfires, Maf, fuel trims, engine speed so far and they all looked fine.
Any help much appreciated folks

[Scottymon]

Have you checked the condition of your HPFP sensor? and when was the last time you did the Cam Follower?

Also how's the voltage on the battery?

[Rawson]

I can't say I've checked that sensor. Cam follower was changed not long after a I purchased the car. Battery voltage is fine.
The car is currently being investigated by my mechanics so will report back on what they find

[GTI_Kyle]

Clutch switch? or Throttle position sensor?

[Rawson]

Where would I find the clutch switch? I thought edition 30 did not have one, couldn't find anything about them online!
And where would the throttle position sensor be?
Thanks

[pudding]

On or behind the pedal.   They do have a clutch switch, primarily for cruise control I think, but (thank god) the ED30 didn't get that piece of sh*t stop-start crap, whereas the S3 did.

Throttle sensor is part of the throttle body. I doubt it's that, or the pedal.  Neither are serviceable.

If it's not an air leak or anything obvious, you'll need to take it somewhere for some live diagnostics.

[Rawson]

I've found out the clutch switch is on the clutch master cylinder,
Will check that when I get a chance, it's currently in the mechanics so hopefully they find and fix the problem

[GTI_Kyle]

Did you manage to get this sorted mate? My cupra has very similar symptoms ,random stalling & blips of throttle etc 

[Rawson]

I picked it up from the mechanics yesterday, they changed the fuel filter and also the low fuel pressure sensor as they said there was a drop in fuel before it cut out.
However on the way home I noticed it is still slightly revving by itself like before, but it has not cut out yet so I guess they are two different problems.
Need to have a look at the clutch switch next I think

[GTI_Kyle]

I've already replaced my clutch switch mate, and mines still the same so i'd save your money if I was you.

I'm thinking its a throttle issue, throttle body might need a clean & alignment. Mines booked in for next week, failing that throttle position sensor. I'll let you know how I get on...

[GTI_Kyle]

Have you checked the condition of your HPFP sensor? and when was the last time you did the Cam Follower?

Also how's the voltage on the battery?

How would the voltage battery affect this? I was told when my car got mapped my battery had a low voltage, would this be a factor to this problem?

[pudding]

You two got intake kits?

[GTI_Kyle]

You two got intake kits?

Yea mate revo kit

[pudding]

Sounds like it's going lean coming down to idle and the ECU is struggling to 'catch' it, so stalls or over compensates (over revving).

Need to log the MAF and lambda regulator channels in VCDS and see what numbers you get as the revs fall to idle.  MAF is usually around 3-4gs with the stock airbox and lambda activity should be small.  If it jumps up a large amount 15% or more, it's defo lean, or the MAF scaling isn't right.

Bung the factory airbox on for a test, to see if the problem goes away?

[GTI_Kyle]

Sounds like it's going lean coming down to idle and the ECU is struggling to 'catch' it, so stalls or over compensates (over revving).

Need to log the MAF and lambda regulator channels in VCDS and see what numbers you get as the revs fall to idle.  MAF is usually around 3-4gs with the stock airbox and lambda activity should be small.  If it jumps up a large amount 15% or more, it's defo lean, or the MAF scaling isn't right.

Bung the factory airbox on for a test, to see if the problem goes away?

What would cause it to go lean? Only reason why I think mine is something to do with the throttle, is because sometimes on part throttle at motorway speeds it feels like its fluctuating/jerking