Hello all, new forum member here from Ottawa Canada. Own 1997 XJ6 with 197,000 km on the clock.

I'm having some funky engine issues.

1. Engine will sometimes stall for no apparent reason. This usually happens when the engine is warm but will occasionally happen within 1-2 minutes after a cold start. The crank position sensor was replaced 4 years ago with an OEM sensor from my local Jag dealer.

2. When the engine is cold (and not randomly stalling) it runs like a champ. Very smooth acceleration and all the power that is to be expected from the AJ16. When the engine is hot acceleration from a standstill will sometimes be jerky and not as smooth as when the engine is cold.

3. When the engine is hot the gas pedal is really stiff. It has a sort of "sticky" feeling. Gas pedal is smooth and not stiff when the engine is cold. The XJ6 was put away for the winter months from October of last year. I've lubricated the external linkages to no avail.

4. Just before putting the car away for the winter the engine would seem to stall when driving along. When this happened the tachometer momentarily dropped to zero and then immediately picked up again to proper RPM. Occasionally, while driving, all the dashboard warning lights would turn on for a few seconds and then turn off. Sometimes the seatbelt/air bag light would stay on until I manually restarted the car. The last time this happened the transmission failure light came on and stayed on. The TCM had become damaged (occasionally I'd lose all but 2nd gear and I could hear the relays inside the TCM clicking away with a mind of their own). My local Jag technician (an independent who until a year ago was lead tech at the local Jag dealer) diagnosed the bad TCM and I installed a used TCM. Transmission works perfectly now.

I installed two cheap ignition coils a year ago. I'm not sure whether my stalling issues are due to a bad coil or to a temperamental crank position sensor. I would have thought an OEM replacement crank sensor should last more than 4 years. Spark plugs are the requisite Champions and are only a year old. Throttle position sensor and idle controller valve were replaced 3 years ago and were calibrated at the Jag dealer. Oxygen sensors are 3 years old. There are no malfunction indicator codes according to my code scanner.

And finally my questions:

1) Would a bad ignition coil cause intermittent stalling at both idle and higher RPMs?

2) What is the expected life of an OEM crank position sensor and is it common for them to fail after as little as 4 years?

3) From what I've read on the forum the weird dashboard warning light behaviour may be caused by a bad ignition coil. Would an ignition coil that caused this issue be able to cause a failure of the TCM?


Other than than the issues above the car is running great. Last year I replaced suspension springs and shocks and the U-Joints on the rear axles. New brake discs and pads all around were fitted last year too. The air conditioning is still ice-cold and has never been recharged - quite amazing in my experience.

 

I really must thank my fellow forum members. Last night I finally went outside and started up the XJ6 and, sure enough, saw a light-show from one of my coils. I replaced the coil and the engine now runs perfectly. No stalling, no momentary 0 RPM on the tachometer, no intermittent dashboard warning lights sequencing on and off.

I never would have believed a faulty coil could cause all these problems before I stumbled across this forum. The coil I replaced was, as most of you will have correctly assumed, a cheap one. It had been fitted for only 5 months before it began giving me problems.

 

Did you take the plastic cover off after dark and look for the light show?

 

I sure did. The coil in question had a translucent potting compound on its top and it was easy to see the flashing light through the compound. I'm not sure if a flashing light would have been visible through the black potting compound on other coils.

Car has been running great ever since. With the exception of the ac compressor that self destructed this past weekend. This will be repaired next week.