pphan3

With regards to my 2000 jeep cherokee 4.0 with 178,000 miles, I was recently having high idle issues at start-up (1000 RPM) and when I drove, I noticed a higher idle when foot was off the pedal in drive (car driving by itself essentially). When placed in park after driving for a few minutes, the RPM would jump to 1800-2000 RPM. When driving and applying the brakes, the RPM doesn't seem to want to drop as much as before. I also noticed an intermittent burning smell (like a burnt rubber or plastic smell) only after driving for least 30 minutes or so. The smell seems to come from the front of the car (engine?). The burning smell did not appear when driving short-distance trips of less than 30 minutes at a time.

Since then, I've done the following

New Parts that I just installed:

• Mopar Throttle Position Sensor
• Standard Motor Products AC176 Idle Air Control Valve
• PCV/CCV elbows with new grommets
• PCV crankcase tube and filter
• Cleaned Throttle Body
• Checked vacuum hoses around intake manifold/throttle body area for leaks (none detected when spraying carb cleaner when engine is running)
• Added Super Tech Fuel Injector Cleaner
• Disconnected Battery and applied negative and positive terminals against each other for 30 seconds.

After doing the above, the start-up the engine idle seems normal (500-600 range), however, after driving for a few minutes and placing the vehicle into park, I noticed the idle jumps up to around 1400-1500 RPM. So there is improvement from original symptoms, however the high idle is still there.

Any thoughts on what other areas that could be causing this along with the burning smell? Could the MAP sensor and/or coolant temperature sensor be possible culprits?

-Phil

awg

are you sure the throttle cable isnt somehow jamming. or something else weird?

I would observe cold idle butterfly/cable position, keep filter loose so you can inspect by side of road

same for burning smell, have a good sniff around, also feel/smell the front wheels, jamming brake calipers is what cause a bad burning smell on XJs

pphan3

Thanks - good call on the throttle cable. I adjusted it and it seems to run good now. No more high idle in park or when I brake. I will look more into the burning smell. I didn't smell anything after driving for 20 minutes...hopefully it stays that way.

awg

inspect ALL the cables

There is one that attaches by a brittle piece of plastic on the side of the AW4. I think its the kickdown cable, under the vehicle, thinks its near the exhaust,

If this s part fails, your vehicle will be undrivable

I personally like to introduce some spray lube at each end of cables

check your accelerator pedal isnt jamming on something like carpet

just touch each front wheel if u smell burning, you can feel if one is hot, the caliper is not retracting due to groove in knuckle

KevinPerry

How is everything going?

pphan3

So far so good. I've driven 100 miles or so since then and haven't encountered any burning smell.

robsjeep

Burning smell maybe that of the tranny. high idle may cause excessive torque converter slip then braking or stopped when in gear check that fluid is not burnt by checking odor and color of atf, change if not bright red or if it has burnt odor. failure to change burnt fluid may damage tranny.