Rough Idling/Stalling Mk2 GTI 8v

[peacher]

Own a 1992 8v GTI which has started playing up. Basically it has started stalling all the time over the last few weeks and doesn't seem to matter if it is hot or cold. Driving home from work this evening (35 min drive along the motorway) I came off the slip road and it stalled when I changed down the gears coming to a roundabout (not much fun when you lose your power steering).

Car then nearly stalled another couple of times in the last few miles to my house but managed to catch it by letting the clutch out again (was changing down gears again when it happened). Sat the car on the drive when I got home and blipped the throttle a few times which shot the rev counter above 1000rpm and then when I took my foot off the accelerator it drops back down to almost below 500rpm and almost stalling before bouncing back up to the normal idle speed. The car has just recently been serviced but it is starting to annoy me that I can't drive it anywhere without the revs dropping and it attempting to stall every time I slow down. Anybody got any ideas what could be causing it?

Cheers,

Peter
 

[takethefifth]

Hi,  it sounds like one of the more common things to go wrong on an 8v like the blue temp sensor failing, a vacuum leak from one of the rubber bits or the ISV being faulty/needing cleaning. If you have a search for any of those things you should find more detail about them.

Other than those i would clean up the earths and check the dizzy and coil.

Right i think i got them all this time! Any more for any more?

[rubjonny]

sounds to me like the problem is actually your idle switch, check it clicks when the throttle is closed.  If not, make sure the accellerator cable isn't too tight, the throttle should hit firmly up against the stop when released.  If it still doesn't click, the idle switch is located underneath the throttle body and need adjusting.  Remove the inlet boot, then loosen the 2 screws holding the idle switch in position.  You can either loosen the 2 phillips head screws, or the spline head screws, whichever is easiest for you to reach! Then move the switch till it just clicks as the throttle is closed, and tighten the screws.

If it does click, then check the wiring to the plug behind the throttle body, mine managed to snap 3 times in as many months due to engine movement, so I spliced in a bit more length and its been fine ever since.

You can also check the electrical connections if all seems well, 1st the engine side of the plug shoudl get 5v with the ignition on, and to check the operation of the 2 switches the tbody side of the plug should pass current with the throttle closed, stop when the throttle is opened a bit, then pass current again just before the throttle is wide open

You can also test switch operation with the engine running, hold the throttle open slightly, then press one of the throttle switches, the engine rpm should drop. Release the switch and it should climb up again.