Hi Guys,

I'm new to the forum and new to Jaguar ownership. I just picked up an 03 XJ Sport and I absolutely love it! Well, at least until this morning when I started it. Lol

It was a little colder this morning (around 45*) when I started the car. Immediately, it coughed and started idling rough and when the engine skipped it seemed to backfire though the throttle body. After about 30 seconds it ran fine and was ok for most of the day although it did idle rough a little when I came to a stop but didn't seem to do the backfire though the throttle body thing.

The car has 128K and the PO told me he used mid-grade fuel in it. I filled it up with 91 octane and ran the tank down to almost empty and then added about $20 worth of 89 octane which is what is in it now.

Anyone have any thoughts?

Thank you in advance.

 

Welcome to the Forum.
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Your XJ could be an X308 or 350/350 - if you tell us in your intro we can move this thread to your car's section.

 

Ok guys, it's been a few weeks since my OP but I believe I have solved the problem.

The backfire I mentioned wasn't a backfire at all. rather, it was the tensioner pulley hitting the stop because the AC condenser was dragging and holding up the serpentine belt.

The funny thing is it doesn't do it when it's warmer out (50*+) or after the engine has run for a few minutes.

Anyway, I'm ordering a rebuilt AC unit from my local parts supplier so it should be all set by next week.

I just wanted to post up in case anyone else experienced this problem.