Wouldn't a failing or failed modulator affect the warm idle as well?

 

And some more:

I did a start of the car, but did not drive. The rpm is about 1500 at start, then goes to about 1400 and then slowly up towards 1600. After a minute or so, the rpms start to decrease slowly to 1300. Everything working fine. Then it reaches a point where it drops toward warm idle of about 800 and starts bouncing and the car seems like it is going to stall. Then, it goes up to about 1200 for about 20 seconds (and running better) and tries the 800 again with the same problem and then bounces back and forth - until engine is warm. Then no idle problems. What is it??

 

It affects everything.

 

A failed modulator will cause this erratic behavior. Cause irt is working off and on. Eventually your car won't even start. You'll just sit there trying to turn it over and over and over...

 

Problems solved.

Three main things: 1) timing belt was loose - so it was tightened. It was making a noise when cold but disappeared once warm. 2) distributor had tiny metal filings in it, perhaps when remanufactured - so it was cleaned. 3) the timing was changed slightly.

Now the car is running perfectly. The cold and warm idle rpms are back to normal!!!

Thanks for all the hints!

 

Metal filings in the dizzy huh? That could cause some shorts, but never a problem I encountered...

 

I think the main problem causing my cold idle problem was the very loose timing belt. When cold the belt was making a ticking noise, but it went away when warmed up - as the jumpy idle went away as well.