VW Golf Mk2 Owners Club

Rough Idle GTI 8v 😫

July 10, 2021, 07:43:07 AM

Hi All,
My Mk2 GTI 8v's idle isnt always where it needs to be. Basically the revs raise to anywhere between 1500 and around 2200 and sit there but when I tap the throttle it drops back down to normal. At first I thought it was the Idle Control Valve so I replaced it with a new part and this made it worse! The revs went to 2500 and when I tapped/blipped the throttle it stayed at the higher mark of around 3500! I have put the old ICV back on now and its back to its old tricks. Does anyone have any ideas please?
Thanks in advance.

Re: Rough Idle GTI 8v 😫

Reply #1 – July 10, 2021, 11:21:43 AM

Hi can't give a fix but my car does the same. I lubricated the throttle control levers and backed of the throttle stop it ticks over at 1000 rpm but won't go lower.
scs

Re: Rough Idle GTI 8v 😫

Reply #2 – July 10, 2021, 11:55:29 AM

Have you checked to make sure the throttle cable is moving freely. Does it need a bit of lube or even replacing?
Does the throttle move freely need lube.
I had this a while back. If I remember correctly a new accelerator cable fixed it.

Re: Rough Idle GTI 8v 😫

Reply #3 – July 10, 2021, 12:20:41 PM

Check the rubber bush on throttle peddle, that the cable connects to. if this is worn it can cause issues.

Re: Rough Idle GTI 8v 😫

Reply #4 – July 10, 2021, 12:21:16 PM

Also check the vac lines, if these are perished could also cause issues.

Re: Rough Idle GTI 8v 😫

Reply #5 – July 12, 2021, 09:32:49 AM

I have fitted a new throttle cable previously so I dont think its that. Its weird, sometimes it does and sonetimes ut doesn't but its really annoying. I'll check the vac lines. Does anyone have a vac line diagram thing (not sure what to call it, like a wiring diagram to show where they are supposed to go) just because I have a sneaking feeling theyr not right 🤔

Re: Rough Idle GTI 8v 😫

Reply #6 – July 12, 2021, 10:19:18 AM

One idea, get some brake cleaner, spray it (sparingly) around the vac system, if there is a hole, the brake cleaner will cause the idle to pick up for a second.

Though be very careful of the exhaust manifold!

Also, is there a throttle position switch on those?
It could be faulty too

Re: Rough Idle GTI 8v 😫

Reply #7 – July 12, 2021, 02:32:21 PM

the small o-ring on the throttle idle screw can often be the culprit in this situation. it goes brittle, distorts, cracks and lets air past. unfortunately replacements don't seem to last so put it on your annual service list of items to check/change.

Re: Rough Idle GTI 8v 😫

Reply #8 – July 13, 2021, 10:59:01 PM

Thank you so much for the replies everyone. Really appreciate it. I'll give both of these suggestions out and hopefully it will sort it but I'll let you know either way 👍🏻. Thanks again