MK3 GTI 8V - 1994 - CUTTING OUT, DODGY IDLE & CHOPPY DRIVE

[blacfist]

Hello 2 all.

i recently bought the above golf gti (2.0l 8v 1994 L reg 112k) with the knowledge that it had an idle problem. what happens exactly is once its warmed up, on idle the revs go from the normal (1000ish mark) suddenly down to about 250. the car shudders then the revs go back up to 1000 or so. the car does this constantly, every 10seconds or so and often cuts out completely when slowing down or reversing. it ALWAYS starts 1st time after cutting out or from standstill. aswell as that, when driving along at a steady speed (say 30mph in 4th gear) the car shudders and bunny hops quite violently until you accelerate. sometimes it hesitates to accelerate other times not. as i said, all this starts once the engine is warm and it never fails to start either from cold or warm, 1st time. when its cold, it idles and drives perfectly. things ive done to try sort it out: got a 2nd hand air flow meter, cleaned it out completely with carb cleaner. changed the fuel injection coolant temp sensor. cleaned the idle valve and cleaned (front side) of the throttle body. also changed the rubber seal in the breather pipe which had split. cleaning the throttle body and/or AFM made the car drive better (smoother, faster) but nothing has got rid of the problem. i also tried removing the hot air intake pipe from the air filter box thinking the car may just prefer cold air as it runs so well when cold, but no change. ive tried disconnecting the air flow meter once is running and it behaves just as badly (with either the original meter or the replacement one) but of course wont start until its reconnected. ive now cleaned both air flow meters and the car runs exactly the same using either of them.
the car was bought as a cheap and cheerful run around for the wife, but as it happens, i really like driving it and have used it far more than i planned to, so id really like to get it running well but i dont want to end up spending what the car cost to buy trying to repair it.
i've read in various forums that coil/ignition module, distributor, ECU relay or resetting the ECU and so on may fix it but im not a mechanic but im happy to get stuck into fairly simple solutions.

any help would be much appreciated.   
thanks

[boneybradley]

Another mk3 with idle problem's......This will be a 2e bosch injection engine? as it's a 94 with an isv..
 looking at your list i will say the following

1. Ecu or fuel pump relay's can go faulty and would be my first thing to check or change.
2. on the dizzy is a hall sender and can make the engine cut out when warm (get the fault codes read this should show up as faulty)
3. the coil's on these car's can crack but that would make the car harder to start when it's wet/damp (unlikely problem) and the best way to check is try another (your local vdub specialist may be best help)
4. If you want to reset the ecu..disconnect the battery for 15 minutes and re connect (this will set the ecu in basic running mode) but I have never known this cure poor running problem's
5. get the timing checked as we have had many car's with incorrect timing recently (due to belt being incorrectly fitted mainly) easyest way to check is rev her above 5000rpm. if she does the timing is more or less ok

keep us updated and we will continue our help and if you want further details on poor idling have a look at this link http://www.golfgtiforum.co.uk/index.php?topic=2080.0

[blacfist]

ok thanks boney,

thats great.

but i think ill have to pass the car to my mechanic. ive printed off all you've said and will get him to through your suggestions in order. ill come back to let you know how things turned.

many thanks for your time.

oh yeah, its the 2e engine with the bosch afm as you said.

[blacfist]

just to let you all know it turned out to be either the fuel pump or ECU relays. i changed both at the same time and the problem of crappy idling and bunnyhopping ride seems to have gone away.

whilst i was there i also changed the HT leads and sparks plugs, completely removed and cleaned the throttle body  and have replaced the standard air box with a JR air filter. the car drivers great now - AT LAST!!

got another problem though, electrical this time and its not really the end of the world, more annoying than anything else, but i will post this on a separate post.

thanks for your advice.

regards