I have a 1990 jeep cherokee . The problem im having is sometimes lately the rpm.s rev real high. and no matter what I try to get it back to normal it doesnt work. The throttel not stuck but thats what it sounds like. Then a couple days later it will be fine. Any ideas . Thanks
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are you saying idle controls are out of control or engine power lacks. ? here is everywhere? if RPM Rises and car does not speed up that is transmission slip. driveablity problems are the most complex. cept maybe noise.
we cant test drive it ,so it behoove that you tell the full story , driving all those complex details. of speed, power, misfiring, etc. even RPM matters. real numbers stated.
If car is stick shift?, like mine was that year then its bad clutch if it slips.
why not ask a shop this. (live help is amazing) or get a tune up,, if you skip them.
Maybe the Throttle Position Sensor (TPS) if the computer thinks it is all the way to the floor then the gears would not shift until the engine RPM is real high. Also would not be able to determine the car is supposed to be idling. Do you have a check engine light? If you do this may come up on a scanner.
You are hitting the rev limiter top range, which cuts off your ignition.
I have a 2001 Grand Cherokee and the problem drives me crazy, but it is the way the car is designed- as soon as you hit the rev limit, it shuts down ignition and your jeep will "buck" - a real pain when you are trying to accelerate into traffic!
You have the 4.0L straight six engine, yes?
If so, please take my advice and learn to live with the minor annoyance of the rev limiter- that engine is IMHO the best Chrysler ever made (nearly "bulletproof"!) and it was so reliable you cannot even get it in a jeep now! For decades, that engine was used in welders, tractors, generators...and yes, jeeps... and it is a favorite among mechanics for its durability!
If the problem began before you changed the plugs that they are likely OK...Some engines "like" certain brand plugs better than others. You may have a weak ignition coil. Poor spark will generally show up at higher rpm's. Spark should be blue and have good "snap" to it and should easily bridge a 1/4" gap or better. If fuel was contaminated, it should show up at lower rpm's as well. System cleaners sometimes work but often are added far too late to do any good. (tank can hold up to a gallon of water without noticing it.) I use 3oz of acetone and one oz marvel oil per 10 gallons of fuel about once a month...cheaper and more effective than most cleaners. (and does not "melt" gaskets and seals as legend has it) The vehicle speed sensor can also give you problems but needs testing to determine if it's got any problems. It's difficult to diagnose by remote control, but I hope you benefit form something here!
I have the same Jeep and same problem. The engine was running rough. The Jeep dealer fixed a vacum problem in the manifold and they then decarbonized and cleaned the fuel injectors. After these repairs the idle problem began, it would spike to 2000 rpm while sitting at idle, sometimes it would slowly come down, sometimes I would have to tap the accelerator. I took it back in and they then replaced the throttle motor and reprogrammed the PCM (Power Control Module?) Still same problem. Now they suspect a another vacuum leak and I am taking it back in on Tuesday, will let you know what happens, $ 1,300 so far.