the cherokee xj 1996, has started to misfire randomly.. starts up and works fine a few mins, then starts to misfire, and the RPMs go up and down awkwardly.. and if i press the throttle when its misfiring, I can hear a 'PUCK' sound from the side the air filter is.

Another problem is, while driving, it suddenly loses power, the engine is up and running but there is no power to the wheels, it doesn't even go backwards in reverse, there is some power to the wheels.. but it just starts 'moving' at about 3 to 4K RPMs. After shutting it off for like 2 to 3 mins and turning it back on, everything comes back to normal, even the misfiring sometimes.. I ran the check engine code check, and it shows 45 only. I think i've got this code before but I can't seem to find the thread nor what the code is about?

I need the car running and have about 4 hours only! If not, I'll have to arrange some car!

 

The TPS can cause problems like that. But i would start by examining all the vacuum lines.

Also, how long has it been since a tune up? Pull the distributor and look at the rotor and the inside of the cap. Pull each spark plug and let us know if there is any color to them.

 

Spark plugs are fine, they have run like 7000 kilometers only, the inside of the cap was also good and clean. Still, I cleaned the contacts of the cap and the rotor. Air filter is good too.
And if the plugs / things weren't good, why would it run fine for sometime and go back to the idiotic behavior?
What is code 45 btw?

 

Any other ideas people?!

 

Might try fuel cleaner in the tank and the pop noises could coming from sticky valves. I used mavel mystery oil to keep my valves working and from sticking between oil changes.

 

well, it should run crappy all the time if the plugs were bad, but sometimes heat can effect the resistance of the plug wires.

Not sure what your code is by the way, might try running by autozone and have them hit it with the OBD scanner. I have a book of all the OBD codes.

 

TPS will cause random missfire code. No guarantee, but iv'e been thru this three times, same routine each time-check,check,check--spend money.

 

My platinum plugs only had like 15K on them when they went bad....the car would randomly have a mis....till one day one cylinder just quit. replace the plugs if in dought.

 

When replacing the plugs, never use "high performance" plugs, the 4.0 does not like them. I always use champion truck plugs, way better performance/gas mileage and they are about 1.50 a plug.

 

X2 on the Champions. This is a Jeep you are working on not a Porsche.

 

I'm using the Denso ones matching the stock specs, nothing high performance there. Any ideas on the transmission issue and the code 45 thing?

 

Could be bad plug wire.

 

Are these 4430 truck plugs really better than the RC9YC ?
I have put in some beru with four electrodes (don't remember the number) that i've catched from my spark plug can.
It's running fine.

 

People, I'm still facing the same problem!

 

I have your same problem, it isn't doing it anymore since a while.
Ihave changed cables, sparks, distributor but it didn't affect.
I think it could be the cps not working sometimes, or maybe that control unit under the coil.
It looks like the square wave coming from the cps misses to reach the ecu and shuts down current to the sparks.