Hi Everyone!

I now have a THIRD classic Jaguar that I am the proud owner of. Ii is a 1983 XJ6 Series III with 41,000 original miles. The problem is that it starts and runs fine, until you get to 35 - 45 mph, then the engine "breaks up". My theory is that it needs a new fuel pump. The previous owner replaced both fuel tanks, fuel filter, sonic cleaned all injectors and replaced the ignition system. He did say that he had replaced the fuel pump as well, but I can't stop thinking that is the issue. He suggested maybe the mass air sensor is shot. Do any of you have any ideas/suggestions. As always, I am appreciative of any advice you can offer. I want to keep this one where it belongs, on the road, carrying around its proud Jag owner!

 

An easy place to begin is with the fuel filter. Remove, and empty contents into a clean jar. What you see or don't see will decide your next steps.

A weak fuel pump is plausible, yes.

"Break up" is a little vague.

You're satisfied that the ignition system is 100% ?

Cheers
DD

 

I totally agree! Since I didn't do it myself, I am always a little suspect. My understanding so far, is that the car runs fine, until you get to 35. The previous owner was going to do an LS swap, but I am a purist, and will keep it original and fix the problem and keep, the Jag engine.

 

Little update. I got the car back from the muffler shop today (whole new exhaust). I noticed that the ignition in the dash was loose. I gave it a little jiggle. Drove it on the highway at 65. No issues!