Hi everyone, our 83 xj6 4.2 runs ok but does not seem to want to accelerate. It runs smoothly but reminds me of a car i had that the mechanical advance was stuck in least advance position. I know there is a vacuum unit and i can determine if that is working without a timing light. This car was always garaged but hardly driven before we bought it, (70k mi)especially the last few years. Any thoughts appreciated,thanks

 

Following can impact performance:

Linkage - See if it's properly adjusted.
Fuel filter - if there is a blockage, you'll starve the car of fuel
vacuum leaks - old broken vacuum hoses will cause the engine to under perform

 

Hey, your reply reminded me i have a new fuel filter hadn't installed because no manual for this car. This will be my next step,thanks!

 

Also check for vacuum leaks, on an old Mercedes that I owned, there was a huge chunk missing on one of my vacuum hoses. It did not cause a miss or rough running, but the performance improvement was amazing after I replaced that hose.

 

If you take the top off the distributor, you should be able to tell if the auto-advance is stuck by twisting the rotor in the centre that activates the reluctor. Twist forward to advance and release, it should snap back on the springs to the normal position. Most Lucas distributors need a drop of oil down the centre every so often to keep it free and working.

 

Thanks for that, another check i had forgotten about doing. Having this forum is great! Thanks

 

Well, replaced fuel filter today and checked for vacuum leaks/bad hoses, did not find any. Started to pull distributor, found top phillips screw has slots rounded out, guess someone tried without success earlier. This is not going to be easy, but makes me think cap and rotor really need to be changed. Going to tackle this manana

 

Finally got distributor cap off.(top least accessible screw head was completely stripped out) was able to checkmechanical advance , which was not functioning smoothly.seemed to stick at different points. Replaced cap and rotor with new. Guess what? Ran worse than when i started! Double checked to make sure i hadn't switched wires on cap. After running a while it smoothed out. On test drive still sluggish, would not go past 4000 rpm when held in first. Any ideas anyone?