Rough idle when warm?

[pullafacial]

Hi guys, hoping someone may be able to help me with a problem I've got with my '90 mk2 gti 16v.
Basically, it runs and starts fine when cold.
As soon as it warms up however, it idles really lumpy to the point where it will even cut out at junctions etc.
The hotter it gets, the worse it gets.
It's almost as if the engine doesn't realise it's warm and is running as if it was on choke?
It's also using loads of fuel which would back that up.

Is there a sensor or something that I could check?

Any help greatly appreciated as I'm pulling my hair out!

Steve

[raferackstraw]

there are 3 sensors on the g/box end of head, 1 is for coolant temp guage, 1 for isv control circuit and a n other i cant remember, if coolant gauge is ok [which is red/yellow wire to one of sensors] then put that wire to the other sensors and if it stops working then that your duff sensor.
but.... first make sure timing,plugs, dizzy ok
other stuff to check are warm up regulator [wur] but you need test guage to check that
oops forgot the usual culprit of idling probs the isv[idle stabiliser valve] do this first

[pullafacial]

Thank you, that's a big help.

I just wonder if any of the above could be ruled out due to the problem only occurring when the engine is warm?

Thanks again

[pullafacial]

Ok, quick update.
I have worked out which sensor is for the temp gauge and used the wire from that to check the other 2 sensors. All 3 sensors make the gauge work so presumably confirms they're ok.

I've also checked the isv to make sure it buzzes with ignition on which it does.

Just to be sure, I removed it anyway and filled it with petrol a few time shaking it to empty.

Still not working! Grrrrr!

[gazareth]

have you checked your air filter? could be clogged solid.

[pullafacial]

Yeah replaced that a couple of weeks ago.

I did notice a flap in the airbox that was broken.
Looked like it should be controlled by an air pipe.

[gazareth]

yeah that will be for the warm air feed from exhaust manifold. shouldn't affect engine running much though. well not to the extent your describing.

[pullafacial]

Proper scratching my head now!

[gazareth]

try unplugging the fifth injector when engine is warm and see if that helps.

[pullafacial]

Thanks, I'll give that a try tomorow.

What does the fifth injector look like and where will I find it?