Volkswagen Golf GTI - Rough idle

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Mon 22 Apr 2013 19:56
Volkswagen Golf GTI - Rough idle - Coopers Mk2

Hello - I am new to the Forum and hope someone out there can help me coz I'm at my wits end!

My '89 Mk2 Golf GTi has a rough ideling problem that started last Dec when it was trying to cut out at every juntion and eventually did when I couldnt start it for about 20 mins. After reading many other Forums and several hundred pounds later, I have so far: replaced the coil, HT leads, spark plugs, distributor unit +cap+ rotor arm, fuel pressure regulator, blue chip sensor, knock sensor, checked all vaccuum pipes for leaks - one was replaced, tried 2 new ISV (made no difference, with the original being better than the new ones), cleaned out and re-set the (original) ISV, cleaned out the throttle body, 'spaceship', rocker cover vent grill, and air flow meter; checked that the micro switches 'click', had a diagnostic timing/mixture/tickover set up, had a compression test and pressure test (the latter found cylinders slightly down on perfect but car is 24yrs old!). Also had a new exhaust manifold fitted as the old one was blowing severly.

No problem starting, cold or hot. No accelleration problems. The car now does not cut out but most of the time the idle drops to around 500rpm then picks back up. This the drop in revs occurs momentarily but on a consistent cycle. Very occasionally the car stops doing this but only briefly.

Can someone tell me if this is electrical or fuel related? I have not had the ECU tested but it feels like it is something really simple - if only I could find it!!

Thank you for any advice.

Al.

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Mon 22 Apr 2013 22:00
Volkswagen Golf GTI - Rough idle - Cyd

Air leak through (perished?) throttle shaft seals ??

Try sealing the throttle shaft ends with vaseline to see if it cures it. If it does try and source a seal kit or replacement body.

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Mon 22 Apr 2013 22:23
Volkswagen Golf GTI - Rough idle - Coopers Mk2

Hi

Thanks for your reply. Not sure I know exactly where you mean, is this arond the throttle body? I am certainly keen to try your suggestion.

I have sprayed all joints and pipes and injectors with carb cleaner spray, this had no effect.

Thanks, Al

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Mon 22 Apr 2013 23:00
Volkswagen Golf GTI - Rough idle - Cyd

eerrr! throttle butterfly is mounted on a throttle shaft which in turn passes right through th ecentre of the throttle body !!! The shaft is selaed at both ends to prevent air (and dirt) ingress.

Manufaturers of throttle bodies chemically test warranty returned bodies for signs they've ben cleaned with solvents. Any signs of solvent and the warranty claim is rejected. Cleaning the throttle body is a good thing, but it needs to b done carefully and should not be swamped with spray solvent.

If you can't seal the ends of the shaft because of the throttle cable mechanism and springs etc, then try spraying spray grease into the running clearance inside. Allow the solvents to dry off and then see if that helps. If it does you need to reseal the shaft.

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Mon 22 Apr 2013 23:07
Volkswagen Golf GTI - Rough idle - Coopers Mk2

Ok, I was in the right place :-)

Thanks for this advice - I'm guessing, that there are lots of guys out there using carb cleaner to clean out various parts without knowing this. Will try what you suggest and get back toy you.

Thanks again!

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Mon 22 Apr 2013 23:22
Volkswagen Golf GTI - Rough idle - Cyd

I'm guessing, that there are lots of guys out there using carb cleaner to clean out various parts without knowing this.

Correct!

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