1992 v12-had been running as good as it can when a nice hot day the car started to lose power. The car does not go over 3000 rpm at hard acceleration but if you feather the gas pedal you can accelerate just fine-step on the gas pedal hard and nothing. I have had some problems early in the year and the tps and upper mount I had to free it from sticking, it seemed to work just fine. I have also installed all new wires cap rotor coils plus filters early in the year as well. the hotter the engine gets the worse it runs.

thanks in advance
Mark

 

Mark, if you have a voltmeter you can easily check to TPS for "drop outs". Post back if you want more details on that.

Was a fuel filter included in your recent service? If so was it clogged? Either way, check it again. Remove it a pour the contents into a clean jar. If you have crud in the fuel then you know which direction to go.

Sometimes a weak/failing fuel pump will overheat after running for a period of time, resulting in a fuel pressure drop. A pressure test is called for and will confirm a problem....although doing so it a bit of a PITA on these cars .....and you'll have to drive around with the pressure gauge taped to the windshield to monitor pressure when when the problem actually occurs. Or you could just replace the fuel pump....but that's a rather expensive guess.

Others will come along with more ideas.

Cheers
DD

 

fuel filter was replaced not long ago, guess its cheap enough to replace..

 

Might not need arbitrary replacing. Remove it, see if it's full of gunk. If it isn't, reinstall it and move on.

Cheers
DD

 

Still thinking this has a lot to do with with the tps, hate to say this but have been thinking about taking the v12 out and replacing it with a ls3 motor with a O/D trans. I hate the low performance-bad fuel mileage-expensive parts-HOT engine-just hard to replace what came with the car from the factory.


Mark

 

IMHO a V8 swap just because your Jag engine is having some driveabilty issues seems like an extreme solution. The TPS can be tested, sensors and wiring tested, you can check fuel pressure, etc. If you have the skill, time, and money for a V8 swap then it's a fair bet that you have the skill, time, and money to make the V12 run properly.

That is, if making the V12 running properly is what you *really* want to do

Is it?

If what you *really* want is more power, a more modern drivetrain, and seeing something you're more famliar with when you open the hood then a V8 swap is a good way to get there. People do it all the time.

Personally I love V8s and have no particular objection the V8 swaps into Jags. And, hey, it's your car, after all. OTOH I also think the Jag V12 is a really neat engine. When I had one I got a lot of satisfaction from learning about it, making it run right, etc. But that's just me!

Cheers
DD

 

I love the feel of power in a car but I was drawn to the looks of the xjs, I have no idea what the cost would be to make more power in this v12 but my guess would be way more than the power you will make. I have a hard time taking this and turn it into something its not, I will do some things next week and see if I can get this car back on its feet for the fall. The mileage on my car just turned 131,000 so the drivetrain does have some miles on her. too bad the v12 jags are not as sought after as some other cars with v12s.

Thanks
Mark