Taif

Hi everyone, my first time here on rennlist so be gentle =)

I have a 964 turbo 1991 3.3L and i have a problem with cold starts.

When i start the car cold i have very low and ruff idle (400rpm), the car drives hesitens and ruff, it feels like it gets to much fuel. After a couple of minutes of driving and the car gets to right tempreratur the problem goes away and the idle is 800-900rpm. What could this be? Wur? Pressure transmitter?

My stock boost gauge is stuck on 0.7 bar, is the boost gauge linked with the injection? If it is maybe that´s way it gets to much fuel on cold starts.

It would be great to get some help from you guys, i have been dealing with this problem for a while now.

Thank you. // Taif

Metal Guru

Taif,
We are a group of gentle souls here (well, except for JamesE ) so no worries.
Sounds to me like the AAV (Aux Air Valve) is kaput. The AAV is on the right side of the engine, between cylinder #5 and 6 intake runners and has an a 3/4 inch air line that runs up to the intercooler.
It allows some air to bypass the throttle during warm-up so that the engine idles faster.
Can anyone help me out by posting a picture of the AAV for Taif?

Francisco Martinez

You can test if it is working by clamping the hose coming out straight from the right side of the intercooler. The hose then bends down and connects to the AAV. If you clamp it when started cold and there is no difference on the engine RPM then at least you can validate that it is in fact not opening. I am having the same problem, the AAV is like $1K last time I checked but I have not taken the time to take it out and clean it and see if it starts working again.

John McM

If I remember correctly, when I had cold start problems I had my mechanic check the AAV. He found the fault was in my Turbo Control Unit, as there was no voltage being supplied to the AAV. The fault in the Turbo Control Unit was a relay, which I replaced for ~ USD 20 in total.

https://rennlist.com/forums/964-turb...trol-unit.html

Metal Guru

Another way to test is to look into the business end of the AAV. When cold it should be open. There's a rotary block-off plate that closes based on a heating element that it's attached to. If it's closed then as mentioned by John check for voltage to it. If voltage is present it might be salvaged by cleaning as Francisco stated. If it's open, then you have a different issue