mY 97 XJ 4.0 HAS DEVELOPED A NASTY MISFIRE. WHEN I BUT IT ON A FAULT CODE READER IT READS -P0101 WHICH IS THE MASS AIR FLOW.
i HAVE REPLACED THE MAF SENSOR,THE THROTTLE BODY,THE IDLE SENSOR,THE THROTTLE POSITION SENSOR,THE IGNITION COIL,THE DISTRIBUTER CAP,THE ROTOR ARM BUT STILL THE FAULT PERSISTS.
wHEN I CLEAR THE CODE IT JUST REAPPEARS AFTER A FEW MINUTES OF DRIVING. THE ENGINE ALSO RUNS VERY BADLY FROM TIME TO TIME, IE. IT MIGHT RUN FINE NOW BUT RUN CRAP IN 10 MILES.
I JUST DONT KNOW WHAT TO DO NEXT AND IT STARTING TO GET CLOSE TO THE TIME WHERE IT MIGHT JUST CATCH FIRE AND BURN TO A SHELL ON A QUIET BACK ROAD A FEW MILES FROM HOME.
ANY AND ALL HELP WOULD BE GREATLY APPRECIEATED. PLEASE,PLEASE HELP

 

OUUUUCH! My EYES! that's alot of yelling.... what did you say? Looks like something about a misfire and a maf sensor code... Do you maybe have a collapsed lifter? bent pushrod? wiped out lobe on your cam? take the valve cover off and turn it over by hand, make sure you don't have any valves sticking and they're all opening the same amount. if they are, check for slack in the timing chain, and check the wear pattern on your drive gear on your distributor.

 

PS - This can also happen if you've got a vacuum leak. especially at the throttle body gasket or intake gasket.

 

Thank you for the reply, I have spent all afternoon looking for a vacume leak with no success.Do you have any other idea's. Is it possable that the head gasket is gone between two cylinders. It seems to come and go for no reason that I can find.
All help is greatfully received.
Adrian

 

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