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my guess, car unseen.
car has an A/T trans, and all A/T jump from park to drive
selection is made on a cold engine, due to the very fast idle speed.
what was the park and cold idle speed. and out door temps.
the lower out door temps, make idle speed , cold engine, even higher
but when the engine reaches 180F or more and holds, the RPM
is about 800 RPM (the FSM tells the exact amount and does vary for the unstated engine option) so at 800 the tranny don;t lurch, did it on a hot engine. so if idle speeds are wrong say so and say it with engine temps. or its all meaningless.
next :
runs rough, the engine (even parked?) is called misfire.
misfire on a good engine (full compression)
is:
1: bad spark (or never had a tune up ever) every 60k miles.
2: bad fueling. too rich, too lean (low idle) bad injectors (stuck or clogged, or wrong fuel pump pressure or bad Fuel pressure regulator)
3: bad fuel.
there is a test for each possible failure. all very simple test.
it takes $80 in gauge tools to find engine problems.
Hi there: Sound like a problem with the IAC valve, this device control idle speed. Base idle is determined by the amount of air that gets around the closed throttle plates. The computer opens the IAC valve to admit more air as necessary to raise the engine rpm.
The IAC valve is located on the side of the throttle body...
Additionally, I suggest scanned the compouter to know if some fault codes is stored there.
Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.
usually rough Idle is not noticable at high ildle. Once it is idles normally try Disconnecting one injector at a time. If the idle stays the same than that cylinder is the culprit. Remove that spark. If it is wet than do a compression test. Should read better than 100lbs of compression.If compression is good take a spark plug and hook it into the end of the plug wire.Lay it across the intake,start the car and watch for spark. If you have spark than you probably have a bad injector. A miss will cause the vehicle to idle high. The computer is trying to keep the car from dieing out. Hope this helps. No spark do a tune up.
Fuel system should be ok. check for air leaks around throttle body, make sure TBI gasket or o-ring are not sucking air which will cause high RPM's, also check for vaccum leaks.
I don 't know if I can solve it, but I had a very similar problem on a 2002 Grd Cherokee Laredo. It ended up being the Throttle Positioning Sensor (TPS). Unfortunately the part alone is about $125 and and total installed cost was about $250. It would idle high at first, then gradually work it self down to a normal idle. Once it was warmed up it it would have an up and down RPM during idling, and several times it stalled out at intersections. There was also a lot of transmission clunking going on when you put it in reverse or drive.
Runs like a dream now. Clunking is gone and idle speed is just right.
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