i have a 90' gxl. 145k. when i start it in the morn it jumps to 4krpm for like 4 seconds and then immediately falls to 1500rpm where it begins to go up and down (1000rpm to1600rpm) it does this til the car is warm. when it finally warms, it idles at 1400rpm (too high!) o2 sensor? TPS? how do i fix it?

 

1400rpm is high, try your air idle adjustment screw to lower that some. Your problem with the idle bouncing deals with vacuum lines. Just place them all with brand new silicon lines.

 

Mine fluctuated the same way. As soon as I got the TPS adjusted correctly and the idle speed set to 800, the fluctuations went away. If you do this and still get fluctuations, check thoroughly for vacuum leaks and also check the function of the BAC.

 

hey chuck are you running any block off plates or bov or boost gauge???