That's called surging, it is caused by a vacuum leak.
Check all your hoses, then spray some carb cleaner around the intake listening for differences in the engine noise. If there is a leak in the intake the chemical will be drawn into the engine and cause it to run faster.
It could also be something as simple as a missing or bad oil cap.
It will idle as low as 600 rpm.It will idle as low as 600 rpm.
The idle speed is computer controlled. If the idle is too low, there is a problem with a ssensor or the idle speed motor.
filter change low oil front pump
whats the problem for my 94 ford van engine high and low idle
Idle may have to be relearned. Did it recently go dead or did you change battery?
why does my 4.75 BRIGGS & STRATTON lawnmower engine idles high and low when cutting my grass
Bad idle may refer to many things. Generally it means the idle is too high, too low, or there are misfires.
Probablty low on coolant. Check the level after the engine has cooled.
The transfer case does, yes.
There is not a low idle screw. The computer sends a signal to the idle air control motor and it does the adjusting accordingly. If your idle is to high and your check engine light is on then you need to go to a repair shop and have them diagnosis the problem.
The idle speed is computer controlled. There is no adjustment. If the speed is too high or low, there is a sensor/actuator/wiring issue.
Had a Jeep in the shop here with that problem last week and it turned out to be low fuel pressure. Try running a fuel pressure test. The Jeep would idle ok but when you tried to accelerate the engine would stall.