Engine self revving while idle (with Video).

**Diofix** · 12-08-2013, 09:48 PM

Hi all,

I've had my 02 MK4 GTI for about a week now and tonight while on my way to Coles I noticed the engine was revving it self. At the first set of lights it was only revving up to about 1100rpm so I thought it was just the engine bumping up the revs to warm up the engine.

When I got back into the car (at this stage the car was warm at 90) I noticed that it began doing the same thing, but was bumping the revs even higher, the highest being about 2200rpm.

I managed to get it home fine but I did notice at the lights it kept doing it, while moving these is no issue.

I looked at some other posts and the causes could be MAF, throttle body or a boost leak. Any idea which it may be?

Thanks,
James.

**Golf-Sam** · 12-08-2013, 11:35 PM

things i would do :

- get the car plugged in VAGCOM and checked of faults ..
- check coolant temp sensor
- check thottle body butterfly for dirt/grime

it could be a throttle position sensor or a Idle control valve ..
if you are lucky .. it's just the coolant temp sensor .. and it's tricking the ecu into thinking the car is cold.

best of luck
Sam

**leighaus** · 13-08-2013, 08:38 AM

or ignition amp module

that is connected to the heatsink on the air box..

When i disconnected mine, it started playing with my revs while idle.

**Lito** · 13-08-2013, 09:20 AM

Originally Posted by leighaus

or ignition amp module

that is connected to the heatsink on the air box..

When i disconnected mine, it started playing with my revs while idle.

If you disconnect the icm it should kill the engine as there will be no power to coils afaik. I'd be looking for vacuum leaks, check pcv pipes under the intake manifold, very common to split

**leighaus** · 13-08-2013, 12:39 PM

Originally Posted by Lito

If you disconnect the icm it should kill the engine as there will be no power to coils afaik. I'd be looking for vacuum leaks, check pcv pipes under the intake manifold, very common to split

yea i think you are right on that side of things mate, If he has a pod filter hooked up though, it can give those symptoms.

**Diofix** · 13-08-2013, 05:28 PM

Hi all,

I took the car for another dive when I got back from Uni today, it's still doing it. I noticed that when rolling in gear (not touching the accelerator) it is accelerating by itself. Looks like I'll be on the bus for a few more days

Also the car is completely stock aside from the stereo I put on in the weekend. It started happening yesterday after I had parked the car outside, maybe the strong winds had something to do with it?

**Lito** · 13-08-2013, 05:48 PM

Originally Posted by Diofix

Hi all,

I took the car for another dive when I got back from Uni today, it's still doing it. I noticed that when rolling in gear (not touching the accelerator) it is accelerating by itself. Looks like I'll be on the bus for a few more days

Also the car is completely stock aside from the stereo I put on in the weekend. It started happening yesterday after I had parked the car outside, maybe the strong winds had something to do with it?

I doubt the wind would affect anything, I still think its a vac leak or dirty throttle body. The stock vac lines get very brittle with age, maybe a rodent chewed them when it was parked outside?

**Diofix** · 13-08-2013, 07:45 PM

Originally Posted by Lito

I doubt the wind would affect anything, I still think its a vac leak or dirty throttle body. The stock vac lines get very brittle with age, maybe a rodent chewed them when it was parked outside?

Well now that you mention it there's a cat from up the road that I've seen sitting on the bonnet a few times, that might be the cause.

I agree with you, I think it's the throttle body/vac lines. I'll give my mechanic a call in the morning to see if he can have a look. Being a new car (for me) I don't want to really go about ripping stuff out of the engine bay as I'm not familiar with the car.

Thanks for the help!

**jeremyex_** · 13-08-2013, 11:56 PM

Same thing happened to me. Opened the side of the throttle body up and sprayed the tracks with electrical cleaner and idle returned to normal.. Might as well give the butterfly valve a clean while you're at it too.

**geoff_gti** · 17-08-2013, 01:47 PM

Yes I agree on throttle body. Give it a clean and run a tb alignment (vagcom/vcds etc) if you can & see how that goes. Mine does it intermittently, I find when it does play up a few other little things happen as well like the cruise control stops working temporarily. Normally switching off and restarting seems to reset that though.