Idle Control Valve Bad?
 

After initial startup, idle is unstable. When I take the oil cap off it stays the same. When I jumped the test socket, the idle was rock steady with the oil cap on but horrendous with the cap off (as would be with a vacuum leak). Apparently the ICV is active but I'm not sure its working correctly. Any suggestions? Anything else I can test before replacing the valve. The car runs great except at idle.

You say "after initial startup"-does the idle stabilize after the car is warm?

The chip is programed to start the car at about 1200 RPM and it stays there for about a minute (and is rock solid). After that (but while still cold) the idle is stumbles. After the car is warmed up (as with a long drive) the idle is steadier but not rock solid.

Same happen to me after a professional engine rebuild I can't find the idle RPM when my car is cold and if I try drive it cold feels like crap.

The isv is easy to isolate-you can jump 2 pins on the engine compartment connector or disconnect the plug to disable it. I'd start by disabling the ISV and adjusting idle speed until its spot on. The problem could also be a bad O2 sensor causing the mixture to hunt, but that'd be likewise easy to isolate by unplugging the O2 sensor running the car to see whether it improves. If the ISV is 'live"- that is, you can feel it run, sometimes cleaning it helps.

Greg-In my first post I mentioned that I already isolated the ISV (or is it ICV?) and it ran better (more stable) when cold. Does that mean the ISV is bad? Has anyone cleaned the ISV themselves? What did you use to clean it?

To isolate the idle problem, do the following:

1. Clean the ISV using a spray carb cleaner.
2. Disconnect the O2 sensor.
3. Check the fuel pressure.
4. Check the temp sensor, S/B less than 350 ohms hot.
5. Put the stock chip back in.
6. Check the idle switch, S/B closed @ off throttle.
7. Check the CO w/o the O2 sensor. It should be less
than 1.5% after the CAT.
8. To check the functioning of ISV;
a. Remove ISV and close the ISV butterfly & replace ISV and
start engine w/o ISV connector. After engine is started
plug in connector, idle will increase.
b. Reomve ISV and open ISV butterfly & replace ISV and start
engine w/o connector. After engine is started plug in
connector, idle will decrease.

The results of the above tests should help locate the problem.

Good Luck
Loren
'88 3.2