Hi,

I've been looking through your site trying to find an answer to my problem.
I bought a 1995 XJS 6 cylinder. The car ran great for 3 weeks. Now the car will start and run great as long as you don't try to drive it! Sitting still, I can start the car and tach the engine up to 1600 RPM and it is fine. Any higher on the RPM the car will backfire and then there's an incredible smell of gasoline. If I take my foot off the gas it will continue running just fine.

Here's what's been done so far:
New Cam position sensor
Used Potentiometer in the throttle body
New MAP air flow sensor
New Temperature sensor

The issue has not gone away.
I was reading your forum about adjusting the Potentiometer, but since I've changed it and the problem still exists, I'm thinking that's not the problem.
Fortunately, I have another car to drive.

Any ideas on this one? I'm at a loss...... this car is in really great shape, but it won't go.

Thanks,
Buzz

 

Welcome to the forum Buzz,

I've moved this question from your Intro to XJS forum. Members here with the same model will be able to help.

Graham

 

Hi Buzz,

Sorry no one has chimed in yet on your issue, but as a start I believe your '95 would have the AJ16 engine and therefore should have an OBDII port to attach a diagnostic code reader.

Have you used one to see if there are any fault codes?

 

Have you checked the Fuel Pressure Regulator?

 

+1 on fuel regulator.

I assume that when you replaced the TPS with a used one, the throttle body was cleaned.

How's the exhaust manifold look? Take off the heat shield. The iron manifolds could be severely cracked.

I suspect it's a fueling issue. Regulator is the only thing that makes enough sense. Fuel filter could be an issue, but a long shot.

 

I'll check these things..... Thanks!
It's 20 degrees fahrenheit here today with 20+ MPH winds. It's a little too cold for my bones to crawl under the hood.

I did not check the fuel pressure regulator. I'm assuming it receives a signal from the TPS, so if that's off, the whole thing could be getting incorrect signals. I replaced with a used TPS, although, thanks to your forum, I found one brand new online on Ebay. It ships from England and I'm in the U.S., so it could take a while to get here. I also didn't know Jag used ODBII, so I can use my reader to check it.

This is good information. I'll let you know what I find.

Thanks!
Buzz