Properly testing the AUX air valve

94Floor · 02-27-2008, 07:42 AM

I am trying to determine if my auxilliary air valve is working. The problem I am having is the car is sometimes hard to start I haven't determined if it is when warm or cold: it seems to happen at random. It will start if I crack the throttle and crank it a bit it will start but it seems to be getting a bit worse.

This is for a 1984 944 N/A

So to test this valve:
What voltage should I see at the connector and under what circumstances?

What should the resistance of the valve be?

Is there any kind of fuse or anything that could be blown that provides voltage to this line?

When I originally got the car this wire was either cut or burnt and I fixed it but I never confirmed the workings of this electrically after fixing it. My original post is here:
Burnt IAC or Aux Air valve wire

Thanks!

944 Ecology · 02-27-2008, 07:51 AM

To test the valve, remove it and put it in your freezer. Remove it from the freezer, and, while it is still cold, look through the valve. As it warms up, the valve should close.

To check the electrical part, apply 12vdc to one side and ground to the other while looking through the valve. It should close as the heater warms up.

94Floor · 02-27-2008, 10:31 AM

Mine is the electrical version.

Problem is: to get it out it seems that I would have to take the intake manifold off and that would be a big hassle. I was hoping there would be a "less intrusive" way of testing it...

Slam · 02-28-2008, 12:41 PM

I'd also check for vac leaks. They'll cause all kinds of trouble. If you don't want to take the AAV out, try warming the car up and pinching the hose to it shut. If your idle changes, the AAV would be suspect.

94Floor · 02-28-2008, 02:11 PM

What I did find when checking over the car more carefully is that the vac hose to the fuel dampener was cracked and leaking. When replacing the hose I noticed gas coming out the top of the dampener which obviously means the diaphram inside is failing. The gas trickling out of here and down to the throttle body where it gets its vac signal and perhaps its lack of ability to maintain pressure in the fuel lines when the car is off is causing the problem? Not sure but I ordered a new one and a fuel pressure regulator at the same time to see if that fixes the problem.

I will do the pinch test of the Aux air valve also but I would really like to know what kind of signal I can expect to it to make sure the computer is doing the "right thing", the signal line is intact (after the repair I had to do to it) and then check that the valve is responding properly to the signal. I don't want to assume the signal is good in this case.

Slam · 02-28-2008, 02:45 PM

Turning the ignition key on should (IIRC) send 12V to the AAV and it'll start to close immediately. Yes, it sounds like your dampener and probably your fuel pressure regulator have had it. Gas in them is a sure sign of that. Be very careful removing the old ones from the fuel rail - the rail is delicate, so needs adequate support. You may not have to change the AAV at all. When mine clogged up I shot a can of carb cleaner through it.

Have fun!