Audi 90 Quattro - simonsmith473©
My friend has an Audi 90 Quattro 20v 1990 engine code 7A. The problem is as follows - When the car is left for a while and is started the idle will drop right off and then pick up again (quite often stalls if foot is not on the gas) , this problem is worse first thing in the morning. If the car has been running then restarting everything is fine. The other problem is the idle tends to "race" ie sometimes sits at 1300 rpm. Any ideas ? cheers!
Audi 90 Quattro - Scirocco man
Could be your idle valve or possibly a vacuum leak.
Audi 90 Quattro - simonsmith473©
Audi 90 Quattro - simonsmith473©
I think it could be the idle valve or the throttle valve switch. Can't find any vacuum leaks. Any comments?
Audi 90 Quattro - Scirocco man
You could try the colortune on it to see if the mixture is leaning out at idle..........just a thought?
Audi 90 Quattro - simonsmith473©
Possibly, but it only does it for about a second when starting.
Audi 90 Quattro - TrevorP
Sound like cold start device to me.

- whatever system you have.

In my "yoof", it was manual choke on the carb,
NOw it is temperature sensor on the ECU.

All I know is yours won't be either of those.

What do you have?

Bosch K-Tronic?
Audi 90 Quattro - simonsmith473©
Thats what i thought but it does not have a cold start device(extra injector). It has bosch multi-point injection (thats what its called).
Audi 90 Quattro - Richard Hall
My Coupe 20V developed exactly the same problem last year. I ignored it and (this hardly ever happens) it went away. I suspect a 4 hour high speed motorway thrash may have helped. From what I can remember there is an idle control valve plumbed into the rubber trunking between the air filter housing and plenum chamber, but I never got as far as cleaning it out, which would have been the next step.

Richard Hall
Audi 90 Quattro - simonsmith473©
I suspect this may be the problem but they are extremely expensive to buy and if this turns out not to be the problem a real waste of money.
Audi 90 Quattro - TrevorP
Simon - try
Audi 90 Quattro - simonsmith473©
I've tried the thrash and it hasn't worked. The problem has been there for years, do you think it could be anything else rather than the idle valve?
Audi 90 Quattro - andy2o5
it could be a faulty coolant temp sender situated on the t peice on the water outlet hose at the front left of the engine! £64 at the audi dealer thow,this was only place i found sold them!
Audi 90 Quattro - IanW3
Had a similar problem on my non-Q 20v this weekend. Turned out that one of the little tiny hoses had dropped off the manifold, so I would still suspect an air leak.
The idle valve responds to good clean - is an excellent source of info. Look at 'Engine Probs' for instructions.
If you need to check the temp sender, the one for the ECU is on the rear of the head, just below the brake master cylinder. Resistance is 5000 - 6500 ohms @ 0 deg, 3000 - 4200 ohms @ 10 deg, 2000 - 3000 ohms @ 20 deg. also describes how to extract (and the meaning of) the ECU fault codes.
Audi 90 Quattro - simonsmith_523
Thanks mate . All hoses are intact, i think i might try cleaning out the idle valve or putting a passat one in its place. At least no one said it was icing!
Audi 90 Quattro - carayzee
Try filling it from empty with decent octane petrol and giving it a good 50 mile thrash.


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