i have a 95 ls i recently bought and notice when the motor is warmed up the rpm jumps up and down. does anybody know what i can check for to fix it?

 

check the fast idle thermo valve (disassemble it and bottom out the screw), idle air contol valve (remove and clean the screen), and bleed your cooling system.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eda6 &raquo;</TD></TR><TR><TD CLASS="quote">check the fast idle thermo valve (disassemble it and bottom out the screw), idle air contol valve (remove and clean the screen), and bleed your cooling system. </TD></TR></TABLE>

and also vacuum leaks

 

i checked for a vacuum leak already but what is fast idle thermo valve and idle air contol valve. like where is it located.

 

fitv is underneath your throttle body with coolant lines running to it

iacv is on the back of the intake manifold

 

thanks.

 

i checked all those stated above and it still idles from like 500-1000. can somebody please help my smog is about to due in a week.

 

How did you check them? Did you clean them out with carb cleaner? What about cleaning the bore of the throttlebody?

Some people have said the guts of the FITV can get loose. Drain it's coolant, open the cover on the side, & see if it needs to be tightened.

Set your 'base' idle.
Warm up the engine completely, turn off all accessory loads. Unplug the electrical plug from the IACV; this should almost make the engine stall. Hold 1000rpm then gently drop to idle. Adjust the idle screw (above throttle bore) for 480 rpm. When you plug the IACV back in, it'll go up to where it belongs.

 

thanks, i'll try that tommorow.

 

i wouldn't screw with the idle screw (pardon the pun) until all is checked, cause that's just covering up your problem. if it jumps, all it will do is jump lower if you adjust the idle....check your distributor cap/rotor, spark plugs, and maybe even your plug wires are goin to hell....i had a low idle, then a bouncing idle, and it was all 3 of those....