rpm rise at idle ???
 

Hi guy's

I have an 88 that is acting up any idea ???

1st) the car is stock N/A starts fine goes to fast idle for the first 10 to 15 seconds then drops to 1500 rpm still fine
But stays at 1500 for 1 min. then goes up to 2000 rpm and stays there ??? :mad:

That's kind of a too fast idle for me :confused:

Any idea ???

checked all vacum's and all intake leaks what else ???

Thanks for your input
J-P

If it only occurs when your car is cold, then it's most likely the fast-idle cam on the back of the throttle body (next to the firewall where the throttle cable connects).

If it constantly stays above 750rpm, you need to adjust your throttle position sensor (TPS), and set your idle speed via the screw (usually has a rubber cap over it) on the top of the throttle body.

Also, check your timing, and you may want to adjust your idle mixture a bit richer, via the idle mixture set screw.

In order to adjust the idle mixture, the car must be idling below 1k rpms, or else the timing will be too far advanced and you'll not get an accurate reading (same goes for setting the timing).

As a last resort, replace EVERY vacuum hose on the car, (make sure to replace the restrictor pellet inside the boost sensor line, as well as the check-valve inside the line that goes to the brake-booster on the driver's side) including all the hoses on the vacuum rack. Make sure to seal all the gaskets with silicone (or replace them outright and use hi-tack or a similar product).