Problemmo - Anybody know this one!

[Bosscat]

This problem/fault is proving infuriating - start engine - idles ok - put foot on accelerator - revs fall to 500rpm - will not rev. Appears to allow engine to idle only whilst cold.
Will rev when it begins to warm up but idle still rough! On the open road ECU appears to cut power off above 4000rpm.

Checked Idle stabliser - ohms OK. cleaned it out.
Replaced temp switch for Motronic.

Next is the air temp unit on the inlet manifold.

Any thoughts - appreciated !!!!!!!!!!!!!!!

[andyg plym]

what does it boost to?

[Acidburn]

Hmmm sounds wierd, i've had a 20v before that it would just about idle then when you touched the accelerator it would die, turned out to be the fuel pump gone, you say yours will drive (or thats what it sounds like) so sounds slightly different to my problem.

[Acidburn]

have you checked for a boost leak? or pulled the codes?

[Rusty]

Throttle position sensor, don't think it would start if the MAF was knackered but a good clean on teh wire (spray carb cleaner on it) would help. Another thing is to check all the vacuum hoses that feed the ECU, if one's fallen off then the MAP sensor will not be getting a signal.

[hiltoa]

Sounds like fuel pump to me - will be asking for more fuel while cold remember...

[martinjs]

Disconnect the maf, see if it makes a difference.

[K Simmonds]

Or can you try another MAF? Sounds similar to what mine was doing before I replaced the MAF.

[gedu]

AAN starts without maf, but won't idle. Sounds like fuel pump to me also. Why? when cold you need loads of fuel, when warm you get away with less fuel, but when booting it, you run again out of fuel.

[s2driveruk]

yep, I reckon this is a maf issue, seem to remember trying to drive mine with it unintentionally disconnected and i got about 200yds before thinking what have i done????? plugged it in again and all ok. If yours is either disconnected or sick then might cause the same probs, basically felt like the car was being strangled and didn't want to go...and revs all over the shop but very low.

[S2central.net]

MAF or TPS I reckon are primary candidates... Could also be MAP inside ECU but I'd rule out the other possibilities first.

Might be worth checking that timing is OK -long shot but if belt has jumped it could cause bad running like that....

[Dan_s2_coupe]

Sounds just like mine when the MAF went **** up

[quattronutter]

could be an air leak between maf and turbo intake,check the pipework and codes first

[kwlw]

Any thoughts - appreciated !!!!!!!!!!!!!!!

I would pull the fault codes first. I would agree with other guys on this thread, that fuel pump, TPS and MAF need checking (not even mentioning hoses, some BIG hole must exist in intake to do this).

Sau

[Bosscat]

Problemo

- HUUUM - Lots of thoughts there guys - thanks - some more info I think.

01 - Codes - I have a boost leak code but have had that for ages. do not think it
is related. Will fix in due course. Unless it has just become too great a
drop for the system to handle.

02 - When I start the engine it revs at 900rpm ish - but as soon as you breath on
the the loud peddle - revs drop to 400-500rmp and rough heavy idle!!!

03 - I leave the engine to heat up - then coax it to rev - revs fine - but idle still
a bit rough. (replaced Motronic thermo switch - no effect)

This effect of temperature on its ability to rev suggested a thermo switch ???? I can then drive it around without any problems - but as said at approx 4000rpm ECU appears to know more than I do.

The throttle switch (potentiometer) another thought ????.

Trying to nail this - without creating a financial Black Hole!! ie will test resistance of throttle switch next.

Again Mutchos Grats for the response - let you know how I get on !!

BOSSCAT.