kennystone

Hi
I'm hoping someone will be able to help me with this problem. I have a year 2000 cherokee 2.5 petrol which has a misfire at 2000 rpm. If the vehicle is stationary and you raise the rpm to 2000 when it get there the engine will kind of cut out rather than misfire and will "blip" up and down untill the revs either go above about 2150 or drop down to about 1800 rpm. If the vehicle is being driven along at the time when it gets to 2000 rpm in any gear it will kangaroo along untill the rpm either exceeds or drops down from 2000.

As this fault occurs at a certain rpm rather than at a certain throttle position or a certain speed I have narrowed it down to ignition. I have replaced the distributor cap, the rotor arm, the crankshaft position sensor and the distributor sensor plate with new genuine jeep parts. It has also had new plugs and leads. I have removed each plug lead in turn and carried out the test again with the vehicle only running on 3 cylinders and each time is the same when it gets to 2000 rpm. This eliminates any individulal cylinder/plug/lead being the problem. It has also had a new coil, I have even tried a second new coil just in case the first one was a dud.

I have tried doing the test in darkness just in case there is any arcing that could be detected and found nothing.

I can only think that it may be an ecu issue but can't really warrant the cost of a replacement on a vehicle of this age. I'm hoping that someone is going to say they've had the same problem and can shed some light on this!!

I have also checked and tested the tps and it checks out fine.

freegdr

heres a test you can try you will need a test light 12 ,ground the light run vechicle to 2000 rpm and with the pointed tip of light poke into the dist cap at each plug wire see which wire does not make the motor run worse

freegdr

have you checked it for codes even if light is not on

kennystone

Hi
thanks for the reply, there are no trouble codes stored and when I remove each plug lead in turn and rev to 2000 rpm the problem is the same no matter which lead I remove.
Kenny