1.8GTi Rough Running and Stalling

Hi,

I'm newbie Mk1 owner, I recently bought an '83 1.8 GTi, with 160K on the clock.  I haven't put it on the road yet as I am getting it ready for the MOT.  The engine ran perfectly(never stalled) for the first month but recently it started running rough and cutting out shortly after I start it.

It starts perfectly and runs fine for about 2-3mins, idling between 800-1000rpm.  The engine then starts to struggle and the idle drops to less than 500rpm before cutting out 2-3mins later.  If I give it some throttle I can keep the revs up and it won't cut out but as soon as I let the throttle go it stalls.

I read a lot about fuel filler rust problems but the filler neck shows no signs of rust.  The fuel pump makes plenty of noise so I presume its not the problem.  I also changed the fuel filter recently but this made no difference.  Has anyone had a similar problem or any ideas on what I could check/change??

Thanks

check the easy things first like the fuel relay.

I replaced the fuel pump relay but I'm still having the same problem.  Would it be worth giving the throttle bodies a clean?  Anyone have any other suggestion for simple things I can do to eliminate possible sources of the problem?

pullout one injector and put in a clear bottle, temp plug the hole, then start up the car and watch to see if fuel stops. if fuel stops i would remove the fuel pump, clean and test

I pulled out injector no.1 and started the engine.  The fuel delivery seems fine, even as the engine begins to struggle and idle under 500rpm the fuel spray stays relatively constant.

I also checked for spark.  The spark looks good, it gets erratic as the engine rpm drops.  I'm not sure if this is due to the low idle speed 300-500rpm or an indicator of coil, HT lead trouble.

I also checked the following

Fuel Pump Relay
Fuel Pump Primes when Ignition is switched on and also runs for a second after engine cuts out
Cleaned Throttle bodies
Cleaned and Checked plug gaps

Would I be looking at a sensor problem here?  The fact that the engine only starts to struggle after about 3minutes seems to suggest that something changes as the engine warms up.

I read a bit on the forum about checking in-tank fuel pump filters.  Is this on the Cabriolet models only, would I have one of these an '83 GTI 1.8 DX Engine?

I'm starting to run out of ideas on this one :dontknow:

seems like it could be the idle control valve or something associated with it (pipes and breathers) check all pipes for cracks and bad corrosion.. as the car will idle higher as it warms up and when warm it adjusts.

not 100% sure but i had a similar problem.
something you can do for free though!!
hope this helps..

Thanks for the suggestions,

I squeezed the auxiliary air valve when the engine was cold and warm. When it was cold the revs dropped, when hot the revs stayed the same… So this seems fine!  I also looked at the air hoses in to and around the throttle body, all seems well.

I did the Haynes manual checks on the Dizzy, Coil and Hall Sender with a voltmeter and all seems to spec.

I cleaned up the earth wire on the rocker cover.  The engine seemed to idle a bit better when cold(900 - 1000rpm as opposed to 800 before), but revs still dropped as it warmed up and cutout within minutes.  I also noticed that the battery light did not come on when I turn on the Ignition, it wasn't charging and as a result wouldn't start the car after it cut out.  Any ideas if this could be related?

The Filler neck was replaced on the car in 2000, Does the '83 1.8Dx have an in tank filter/pump like the Cab version as I've read alot of the rusted filler neck horror stories?

Any ideas on what to try next would be appreciated