Possible Idling Issues

christ1

Registered User
I have a 1990 SC, manual with ~250,000 miles.

I am having issues when the car is idling. It will idle at about 700 RPM and at 22 in-Hg. The left most pulley (I don't know what it controls) as a whole spins with the belt. This state lasts for about 2 seconds. Then this left most pulley makes a "click" sound and the outer part continues to spin with the belt, while the inner part of the pulley stops. This is accompanied by an increase in the RPM to 1000 RPM and the boost drops to 19 in-Hg. This state lasts for about two seconds and then "clicks" on. This continuously repeats itself. The change in boost always occurs first and the RPM is always following.

Revving the engine, reversing, or moving in 1st gear doesn't change anything about the regular cycle. When the engine is turned off, the inner part of the pulley will move latterly. There are no warning lights on the dash (including the check engine light).

First of all, what does the left most pulley control? I assume this is not supposed to be occurring, so does anyone have thoughts on a solution? I came across this post that describes a similar problem and the guy's solution. Thanks for the input.
 
Umm...dude, that's your AC compressor. Turn off the climate control completely, (it will also cycle on defrost), and I bet it will run the way you expect.

Nick
 
I guess I am an idiot. And the only reason it started recently is because it got warmer for the spring/summer.
 
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