My 96 XJS 4 liter runs beautifully most of the time. However if I 'floor it' 2 or 3 times in a row it will then idle rough or stall out and the catlytic converters start to glow red hot. If I let it sit overnight it starts up and runs fine. Engine temp reads normal the whole time. If I don't push it hard, I can maintain highway speed and drive in stop and go for an indefinite time with no problems. Again, if I don't accelerate too rapidly all is well. And if I do it seems fine till I slow down. Thoughts?

 

Sounds like overfuelling. I would start by checking the air-mass meter and fuel pressure regulator.

 

I did a quick check through the manual and found the diagnostic section for the air-mass meter. They're calling it an air-flow meter. It's on page 31 of this manual and lists the voltages and expected behaviors.

"http://captainsodium.com/Private/XJS-Manuals/ServiceManuals/04 Engine Management 4.0 litre.pdf"

You could also have plugged converters. Try taking it out and running it on the highway for an hour or two. That may heat the catalysts enough to ash-off any accumulations.

 

Thanks for the reply Sodium. Unfortunately I can't get the URL in your post to work for me. Would love to see it so I could get a handle on where to start. Thanks again!

 

I put an extra hyphen in there. This works.

http://captainsodium.com/Private/XJS...erviceManuals/

 

I've tried IE and Firefox, still no luck. Farthest I can get without a 404 is http://captainsodium.com/Private/ Is it small enough to email?
Thanks again

 

alright. I pulled the space out of the url. This should provide you with nothing but happiness.

http://captainsodium.com/Private/XJS/

 

Sodium thanks for providing the link. Works for me;-)

PM sent.

 

Sodium,
Got 'em. Thanks so much. I'll be under the bonnet this weekend.