94 XJ12 with 83k miles won't start when it's hot

JAKE_GUMM

MEMBER
1994 JAGUAR

My mechanic accidently made the car back fire into the manifold when reving the motor to check to see if the belts had quit sqealing after replacement. Since then it won't start when it's hot. They've had me replace the cap & rotor which didn't have any black or cracks in it, found a small vaccumme hose on the left side that was under the MAF sensor.

When it's cool in the morning its fine but by mid afternoon it won't start hardly, it will cough, shudder, back fire a little and die. I've found it will eventually start if I keep pumping the pedal like I do on my old farm truck and it will fire up and blow smoke out the back that has a strong gas odor to it. Once it's started it runs fine, idles fine it's just restarting it I go through the same process. What should I look at doing next? The VCM is giving fuel fail 13 for the MAP sensor and on this car it's apparently 2000$ as it's attached to the ECU for the entire injection system made just that way for just that car just that year. I'm trying to find another solution before plunking down that kind of cash on it and finding out that it was something else.

Thank you in advance!

Jake

4 Replies

RON MAYFIELD

MEMBER
1 POST

Try finding a used MAP Sensor online or at a Salvage Yard instead of buying a new one. It should only cost around $25. So what if it does not work, if it does you just saved $1575! If you have fuel injection, I am surprised that you can pump the gas and start the car! There are no accelerator pumps on fuel injection. Backfiring through the carbs, if you have them, is another issue, but I would have your air/fuel mixture checked to see if you are within limits.
A well equipped garage should have an exhaust analyzer to determine if you are ok. In my experience, a backfire usually does not cause any harm, just means something is not right with the engine but it could be fuel, ignition or a timing problem.