So I have been having idle problems lately with my 90 22re and just when I think I have it under control, I hit the ac button and the idle starts jumping between 12-1600 rpms! what gives!

Andy

 

in my 90 mazda miata (yea i have a miata) The idle goes up when i put the AC on. Its normal in my car, because the motor works harder to run the AC...hence the lower gas mileage from using AC

 

Well I understand that the idle should go up to compersate for the extra load on the engine but it shouldnt continually surge between 12-1600 rpms.

 

Maybe the fast idle is set too high. Try turning down the A/C fast idle up valve to a lower speed. Usually you want the fast idle w/ A/C on to be just a little faster than the normal idle, maybe +200 RPM or so.

 

My idle drops when the A/C is turned on....i wonder what the deal is with that.

 

Well then bump up the A/C idle up valve setting. Or it could be the VSV that operates that fast idle valve is clogged and not passing vacuum to the idle up valve.

http://www.4crawler.com/4x4/CheapTri...ne_Pix/13.html

 

I didn't know that's what that thing was. I'll try that later today.

I shouldn't have any vacuum problems I had some lines replaced that were bad. Should all be working now.

 

Not uncommon for the fitting to be clogged where it enters the intake plenum. Easy test is to bypass the VSV and just connect the line from the intake to the fitting on the idle up valve. If idle goes up, then the line and fitting are open. Then see if the VSV is open inside, they can get clogged as well.