I've got a Jeep Grand Cherokee 4.7 v8 that has suddenly developed a problem that makes the Jeep idle rough and run bad like it is missing or starved of fuel or something.
On a cold start, where the car has been sat for some time the car will crank and start straight away without any problem. It will rev up on start and settle down as normal. You can rev the engine hard and it is smooth as it should be and you can drive it as normal.
But, (and here is the problem) once the engine starts to warm up a bit and the temperature needle starts to climb (gauge says 40) the revs suddenly drop off to around 500 from around 800 and the engine starts to tick over rough and run rough. Revving the engine hard doesn't clear it.
Once the engine has cooled, if I start it again it will do the same thing, run well until it started to warm and then run rough.
I've changed the air filter to a K&N one, I've changed the spark plugs (although the old ones looked clean and in good order), I've taken the throttle body off and cleaned it out, I've removed and cleaned the Idle air motor and throttle position sensor.
Wednesday, October 10th, 2012 AT 7:59 PM