The most common cause of engine surging (rev up and down) is a dirty air filter.
Hello, Usually The throttle position sensor controls that. When they go bad, your idle will go up and down like that. I hope this is helpful.
The idle speed is computer controlled on a LT1 engine. If it is a little high, try checking for vacuum leaks.
Idle compenstorVehicles hve an idle copensator that speeds up the engine when the ac is turned on to ring the rpm back up to the proper idle speed, if yours is too fast then t needs to be adjsted.
I would look for a vacuum leak under the hood. If the check engine light is on have an auto parts store read the code(s). The code(s) will help you find the source of the problem.
if the ac was on it could lower the idle down the ac takes about 12 horse power to run + As long as the transmission is in "Drive," it provides excess strain to the engine system and at a stop will keep the engine idle a couple hundred RPM lower than in "Park" or "Neutral."
Because it also starts the air conditioning compressor which cycles on and off loading up the engine which changes the idle
your idle air control valve need to replace parts $200 labor $150 or clean it with carburetor spray if you're lucky that might solve the problem i clean my idle air control valve it help little maybe i didn't clean it up good my idle go up and down pretty high and then after i clean it sound much better but it still there idle go up and down slowly now the best way just buy a new idle air control valve engine light turn on hope its not o2sensor
Check Coolant Level It Could Be Low. Also Sounds as If Your Thermostat Is Bad.
locate the idle on your 99 cherokee,then take a flat head screwdriver and turn the idle towards the right to turn the idle down. right now the idle is too high. if you dont know waht the idle looks like it looks like a flat head srew with out the head. located in the front of the engine.
Take a look at your idle. what do you mean take a look at my idle? There is a deal within your engine that controls how much gas goes into the engine when you aren't driving. Google it.
on the left side of the intake is a round cylinder with wires plugged into it. this is the idle control. It is most likely dirty. take it off and clean it out with carb and choke cleaner.