Idle control valve problem results

T86951 · 04-05-2001, 06:31 AM

all winter I was having a problem of rich on cold starts on my '86 NA 944 and suspected the idle control valve and was about to replace it. that would have been a lot of work and about $120 wasted.
What I have found with a lot of sudying and testing is this:
The idle control valve on my car has 3 posts. On a cold start voltage is supplied to the center and top posts which opens the valve to let extra air in. As the car warms up power is shifted from the top post to the center and bottom posts which closes the valve.
Mine is always suppling power to the bottom 2 posts, cold or hot so the valve stays closed hence no extra air on a cold start hence an overrich (actually under supply of air) condition. I can unplug the connector and run 2 wires from my battery and touch them to the top 2 posts and the valve opens and it starts perfect when cold. I can then slide the connector back on after about 30 sec of warming up and it closes it and idles fine.
Now I have to figure out why my computer is not swiching power to the top 2 posts when cold. I have already replced the temp sensor with a new one.
I assume there is a relay somewhere that swiches this but I have no idea where so I am now at a dead end. Anyone have any ideas on this? Help!!!

drew1 · 04-05-2001, 07:54 PM

does the dme send the signals to the control valve based on both time & temp?

drew1

T86951 · 04-06-2001, 10:36 AM

I don't know what makes the signal switch but it isn't switching. I had a friend start the car when cold and I have checked the wires for voltage and it doesn't switch the voltage from the bottom to the top ever. The voltage stays on the bottom 2 all the time which keeps the valve closed. I would guess that whatever switches it is bad but I don't know what are where that is!!!
The good thing is it really doesn't matter in warm weather and it is warm here in KY where I live now. Only in cold weather on first startup in the morning is when it causes a problem.

ch944 · 04-06-2001, 11:13 AM

Will the car start in cold weather or just keep turning over?

CH

Ehab · 04-06-2001, 11:36 AM

I've had the same probelm for quite a while now, but I have an earlier model (84 944), where the aux air valve (AAV) only has 2 wires going to it with battery voltage. I guess the opening and closing is done by the temperature affecting the AAV itself in the engine block.
My car starts fine (running rich, 1000rpm), then once it warms up after like 30 seconds, the RPM drops to low levels (700), until the car warms up a bit more (temp indicator in middle of black zone)then it rises to the normal 900-1000rpm ... I checked the voltages and resistance, but they were fine. Taking the thing out to clean it is a ***** ... and the easier, bur more time consuming, way to do it is to take out the intake manifold!!! Yeah like I have time to do that!!!!
Good luck, and if it is no major problem, I would just deal with it by kicking the accelerator until the car warms up ....
I wish I had a manual (choke) that never breaks down like that ... oh well.

------------------
Lock Stock '84 944 and two smokin' tires ...

ch944 · 04-06-2001, 11:46 AM

Let me reword that. If you do not jump the posts for cold start on the stabilizer valve and it's cold outside will she start or just keep turning over? At what temp are you considering cold? I have the same sickning problem. Anything below 30* for me, however if I jump the car with my charger booster she starts. Temp above freezing, starts right up.
The car runs killer once it starts!

CH

Porsche 951 Fanatic · 04-06-2001, 01:25 PM

Here is a idea i had just a moment ago - you can always get say a 2 way switch that when switched up gives the top two power then when down gives the bottom 2 power - then route it to your interior, or get a device that supplys power for a given amount of time after the ignition has been on then switches, as a temporary fix of course. there may be a sensor that tells the DME the cars temprature and mabey that is messed up or grounding out or whatever and always telling the car its hot, we had the one in our van mess up(gmc safari) and it was telling the DME that it was -40 or so(what the mechanic said) and the car ended up killing the oxygen sensor because it was running rich and also tps was bad, good luck

---
oh you said you replaced the temp switch - was it the one for the gauge? i would imagine the DME has a different one

[This message has been edited by Porsche 951 Fanatic (edited 04-06-2001).]

drew1 · 04-06-2001, 11:24 PM

There are two temp senders, I may be confused but I think the guage has one wire terminal & DME has two wire terminal (with kind of like an injector connector).

Air valves on 944na and 924t are 2 wire. I think they open & close by time.

drew1

T86951 · 04-10-2001, 06:37 AM

The car hits and starts with no problem. It just idles low about 700 rpm's and rich for about 30 seconds and then the rpm's come up to 900 and it runs fine. It happens like below 50 degrees an the colder the worse.
I replaced the temp sensor that goes to the DME (yes it is 2 wire).
The idle control valve on 85.5 and newer cars is a 3 post unlike the early cars that were 2 post.
I could rig up a deal to make it switch but I would like to find and correct the real problem as I know a lot of 944 owners have this problem and I would like to find the cause so I can fix mine but also share with others.