Idle constantly going up and down

[70camaro]

I have a 94 with the 1.0L engine, my electric ISC (idle speed control) motor keeps causing my idle to go up and down. The only thing I've found that has any effect on this, is when I unplug the coolant temp. sensor on the throttlebody. I have replaced this, along with the other coolant temp sensor (in the water neck), and the air temp sensor. Still doin' the up and down dance. Also of note, it only does this AFTER reaching operating temp. Can anybody help on this?

[willyshannon]

If you are lucky it may be just the PCV valve, otherwise it may be a bad throttle body.

[70camaro]

How is an entire throttlebody "bad"?

[bansheetaz]

thats telltale signs of a vacuum leak somewhere.

[willyshannon]

Originally Posted by 70camaro

How is an entire throttlebody "bad"?

obviously there are various components in the throttle body that could cause problems, an "expert" on these cars told me a similar problem with my '94 was caused by a lower throttle body defect that could not be repaired except by replacing it. He mentioned it might be a bad PCV valve that was causing the idle to cycle, then did a test by pulling the hose from the throttle body, and said the PCV valve was fine so it must be the throttle body.
I later purchased a PCV valve just in case, and when I checked the old one I found I could blow through it in either direction. I installed the new one, it solved the problem, and the car runs just fine. Have you replaced yours?

[70camaro]

I have not replaced my PCV yet, but it is now first on the list. I also have heard about haveing to replace the entire throttle body. I just don't "get it". It seems like it would be just one or more components but.... BTW, I'm pretty sure its not a vacuum leak, I can actually see the electric stepper motor move the throttle butterfly, and remember, if I unplug the temp sensor it only idles high, no cycle.

[donaldii]

I had and idle problem, but my idle would go up and down as I was slowing down to stop. I had to replace the isc solenoid. It completely solved the problem.

[willyshannon]

Originally Posted by 70camaro

I have not replaced my PCV yet, but it is now first on the list. I also have heard about haveing to replace the entire throttle body. I just don't "get it". It seems like it would be just one or more components but.... BTW, I'm pretty sure its not a vacuum leak, I can actually see the electric stepper motor move the throttle butterfly, and remember, if I unplug the temp sensor it only idles high, no cycle.

If the problem persists, try the Team Swift forum where there are a number of possibly pertinent discussions.

[70camaro]

Yes, I also have a thread there. Just wanted to get as much input as possible.