I'm having an issue with cylinder 3 misfire (p0303) that I can't seem to solve and have to drive the XJ 1100 miles on Saturday! I've replaced the spark plugs, coils, affected fuel injector, and run a can of Sea Foam. I know for sure that it's not a heat soaking issue cause it still sucks after sitting all night. I'm not losing any coolant and i checked for a cracked cylinder head. I'm going to do a compression test tomorrow morning to see if it's maybe a blown gasket or piston ring?? If that's not the problem i have no idea what to look at next. maybe a sensor? I recently cleaned out my throttle body. Would throttle body cleaner damage any of the sensors? Thank you in advanced for ANY advice!

 

You obviously looked at the cap, rotor and wires. Crank sensor mite be actin up, too. I get a number 1 misfire code every so often in my '97, never amounts to anything and the truck never runs bad

 

SoCalDude, does it start hard at all? does it shut off with a kick at all?

if you're up for throwing another $50-60 at it and 2 hours of time, buy a new Crankshaft Position Sensor, make sure its' MOPAR made, model # 56027865AB (depending on year of your xj... mines 98) call your nearest chrysler dealers to get one local if the misfire concerns you... i hear anything thats not from a dealership and OEM mopar made, is crap if it's an electrical sensor. that crosses out advance/autozone etc or cheaper replacements from ebay.


I just fixed a p0300 p0301 p0302 p0303 p0304 code combo with it... i had already replaced plugs/wires and couldnt discern any other issues. so i put it on and it's been good so far.

see my thread about it here, but i basically already told you everything.

https://www.cherokeeforum.com/f2/fix...0/#post1888404

 

sorry i didn't give enough details...

Its a 2000 4.0 5-speed 4dr. It starts up okay and runs like its on 5 cylinders sounds kind of like a lawn mower (oil pressure is good though). It's doesn't perform very well up hill. shuts down a little rough but nothing too bad.

Would a crysler/Jeep dealership have a CPS in stock?

 

If you have a consistent single-cylinder miss, it probably isn't the CPS. It's something related to that cylinder. What's the plug look like?

 

I've changed the plug twice and the coils. the plug looked a little burnt when i pulled it out but the same as the others.

 

Compression test would be the next thing then.

 

And then Radi will school you on a dixie cup full of water.