My 86 XJ6 is suffering from an intermittent stalling and skipping issue. I just replaced the fuel pump as the old one was noisy. I replaced the fuel filter twice. I have put dry gas and fuel injector cleaner in the tank. It will purr like a kitten for hours and then start to act up again. Any ideas for me?

 

Hi DavidJC,

Intermittent stalling - so the revs drop sufficiently that the engine stops?

Skipping - it starts running roughly? and / or starts to be lumpy?

That it runs well between episodes indicates that fuel probably isn't your problem.

I would check your ignition amplifier. They work well until such time as they malfunction.

I had a similar prognosis and it turned out that said ignition amplifier was flaky and so when it got hot it would play up and shut the engine down. Twenty minutes later I could start the engine like nothing had happened, until it got hot again in half an hour and the whole process repeated.

I also had an underlying problem with brittle and cracked ignition wiring, so replaced the wiring loom shortly thereafter as well.

Cheers,

Nigel

 

+1 on ignition amplifier.

Also, check for vacuum leaks causing lean condition. Likely areas are brake booster, engine oil dipstick and oil filler cap.

You may also want to have a read of the article written Roger Bywater of AJ6 Engineering regarding the Lucas/Bosch EFI system:

Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering

This article does a very nice job of explaining the theory and some of the issues of the L-Jetronic system as fitted to the Series III cars.

 

The 'could be' list might get rather long.

To clarify, are you saying the the misbehavior typically occurs only after the engine has run for quite some time? And it behaves well if has run for shorter periods of time?

If so......

The ignition coil and ignition module (which is inside the ignition amplifier) are both known to act up after absorbing engine heat but work OK otherwise. Also, typically, the engine will not restart until things have cooled down for an hour or so. Not carved in granite, but common.

A couple ideas not related to heat:

Remove the driver's side under-dash trim and with the engine running give the wires at back of the ignition switch a few gentle wiggles. If the engine responds, you've hit pay dirt. A faulty switch...also common.

Examine the wiring and connections at and near the coil. It's usually very brittle from the engine heat. Might find an area where the insulation has cracked off, leaving bare wires touching the engine from time-to-time.

Cheers
DD