98 xj8 with 107,000 miles Im having some problems. I rebuilt the motor and the problem im having is with the mass air flow sensor plug in it will fire then die. It wont idle or rev up. If I unplug the mass air it will fire but it wont rev up above like 3000 rpms but it does idle and the restricted performance light will come on but only bc the mass air is unpluged.( It goes off when plugged in) I swapped out the mass air with a known good one and it stil does the same thing so its not the mass air itself.

Im thinking I have the motor a tooth off on the timing chains but I wanted to see if there was anything anyone thought It could be or if there is a way to check the timing without pulling off front cover. The flats on the cams were flat and the plug was in the driveplate when put in time Im not sure please help thanks in advance

 

Did you check the connector and wiring?

Things have a way of getting banged around when engines are out.

Have you tried a full reset?

And, as it will inevitably be asked .. have you pulled the codes ... and what are they?

 

Are all the vent and vacuum lines installed and tight? If there is a leak, and the MAF is sensing low air volume, but in reality after the MAF there is a massive leak, it wouldn't run- It would run if the MAF was unplugged because I believe it goes into a "safe" mode and doesn't do any compensating based on the MAF reading.