jschick

I am working on a 99 1.8t that seems to run pretty good except it stalls on deceleration. on startup it idles fine, but if you rev it the idle will drop to about 400 and stall, if you idle it down slowly it will go to a normal idle. but tap the gas it will stall as the RPMs drop, I get no codes and have calibrated the throttle body and etc. I can't find any Vac leaks so my guess is the throttle body just isn't reacting properly even though no codes, Any thoughts or suggestions?

jschick

after a little more playing I have found the car idles perfect when cold, it is only when it warms up it will stall or idle will drop down to about 400rpm on deceleration. so maybe temp sensor?? any other ideas? cleaning the throttle body did not help at all

turbo510

That's where I'd start, coolant temp and intake air temp sensors. See if these temps look reasonable with VAG-COM.

jschick

I had a extra air temp sensor and no change, and if it cools down today I will swap out the temp sensor and see what happens

emulsion

But I would think you'd see a vag error, i.e. either mixture too lean or signal too low maybe. If you drive it around does it get better and not stall? Maybe it's still a vac leak, like one of those black and grey plastic valve thingy's. Good luck. I just had my MAF replaced after idle was dipping low after a rev, and now it's a rock solid idle. I was getting an intermittent mixture too lean, then I tried to clean the MAF, then got 'signal too low' so I think I hosed the maf by cleaning it or it was on it's way out. Either way, the new maf fixed my problem.