Audi And Passing Smog

[Jonb390]

Hey can't get my vehicle to pass smog due to it's inability to maintain satble RPM. It needs to stay at around 25 hundred, but it will drift up or down, any ideas, its a A Quattro 1990.

[ctesla]

Jon,
welcome to AF!
when you say RPMs won't hold, you mean all the time?
no change regardless of cold, or warmed up?
does the tach ocasionally act sporadic as well?
is it auto or stick? how many miles?

sounds like it could be a TPS, but before I spent the money,
I'd clean the MAF with some throttle intake cleaner, and pull the horn, and clean the throttle plates as well. (and while doing this maint. I'd pull the fuel pump relay, which will reset air/fuel parameters, and injectors)
then see if she wants to hold idle.

if not, could be the Throttle Position Sensor (if you buy it from AutoZone you'll get a special ordered Bosch unit in the Wells bag for the Wells price: BONUS) or one of the speed sensors on the trans. (these will be dealer only- you might find one through a parts house, or internet, but you never know if they're the correct ones, as I have worked the counters, and the shops, the books and computers are wrong (or VERY ambiguous) and for under $45. you know the dealer to be an accurate component.

hope this helps,
chris
nrt racing