My 1997 XJ 3.2 auto has developed an annoying habit. Drives OK at speed but when you slow down it stops just like the ignition has been turned off? Put it back in N an it starts again. When slowing to stop, the check engine light comes on then goes off. Diagnostics indicated a fault with the ECU. Changed it, still the same. Someone suggested the Air Flow Meter, changed it, still the same.........Anyone have any suggestions please?

 

Have you tried putting the gear lever in neutral when slowing down to see if the engine still stops

 

Hi Richard,

I have moved your thread from the forum for the X350 to the forum for the X300, which is the Jaguar factory project code for your 1997 XJ.

The first thing I would suggest is that you check the transmission fluid, as low transmission fluid has been associated with engine stalling when slowing to a stop or slowing to make a turn. My assumption is that the torque converter fails to disengage, bogging down the engine.

Do you recall the exact code or codes that were scanned that indicated an ECU problem?

Cheers,

Don

 

Spark plugs, my friend. If unknown age or mileage on them, replace them. Old ones WILL cause stalling as you describe. In my experience they only last 20k miles. But they are inexpensive and easy to replace. That job also gives you a chance to check the coils, and the plug wells for oil leaks. Champion RC12YC. $2 apiece.

 

Thanks very much for responding. I did try this and it will still stop. I ran it this morning and on tick over, it runs at around 800RPM for a few minutes, then the revs suddenly drop down to maybe 400 and then pick up, then the engine stops, just like the ignition has been turned off. I have ordered new plugs and some new coil packs, but am clutching at straws a bit!
Really annoying because up to now, the car has not been a problem and I have put 60K on in the last 2 years (only 107,000 on the clock)
Appreciate you trying to help.

 

Don. Thank you for putting this in the correct place. I'm new to this and wasn't sure if I had it in the right place or not. I have previously placed a question about the location of the unit that controls the heated mirrors as mine are on continually, but didn't get an answer. Probably why.
I have just added this to another reply " I ran it this morning and on tick over, it runs at around 800RPM for a few minutes, then the revs suddenly drop down to maybe 400 and then pick up, then the engine stops, just like the ignition has been turned off. I have ordered new plugs and some new coil packs, but am clutching at straws a bit!
Really annoying because up to now, the car has not been a problem and I have put 60K on in the last 2 years (only 107,000 on the clock)
I have checked the gearbox fluid and it is fine. I have asked the mechanic what code came up and he couldn't remember although when he checked the only info that came back said it was the engine ECU. The message on the dash that comes up says "Check Engine" but this goes out each time the revs pick up. Stuck now!!

 

Thanks for taking the time to reply. I have just ordered new plugs and some new coil packs just in case and will see what happens. Many thanks

 

Remove the rubber air intake trunking at the throttle body, wash the oil out of it.

Take a solvent soaked rag and wipe out the throttle body of all the "black goo" that has built up.

This "black goo" can take some serious wiping out. Mine required some careful scraping with a kitchen knife (she found out), and once that internal bore was CLEAN, the idle quality returned to normal.

Whilst you in the area, check carefully ALL the rubber trunking, and the joints, that are between the airflow meter and the throttle body. Any air leaks here will be sensed as "Unmetered Air", and the management system will get hissy.

 

Thanks. My mechanic did say that he had cleaned the throttle body but I will check it over. Appreciate the help

 

If the CEL turns on and off and some kind of diagnostics indicated an ECU fault, I have to believe the problem is LIKELY related to the power supply to the ECU. Either the supply through the relay or the grounding. Or the connector pins. You see, the ECU should retain almost any code, but a power cycle resets some codes.

And, it would be interesting to know exactly WHAT diagnotis lead to the "bad ECU" determination. I know of no code for that!

 

Thanks again for the reply. I have booked the car in with a Jaguar dealer for next week for them to run the diagnostics again. I'll update with findings.

 

Thanks for all the help. I went over all suggestions and it looks like Sleak Jag 12 was on the mark. Despite having changed the ECU and Air Flow meter and cleaning out the throttle body, it still kept stopping. I went back to basics, changed 5 of the 6 plugs (one I can't get out at the moment) and invested in some brand new coil packs. After fitting, started like a dream and as yet (fingers crossed) it has repeated it's dying trick. Runs better than before. I told my mechanic and he was amazed that this seems to have cured the problem. Thanks again everyone

 

May I ask where you bought the coils please? I am also in the UK so it would be handy to know where you got them and what cost.

 

Thank you Richard! And I assume you meant that the car hasn't repeated it's dying trick! Touch burlwood.

Be wary of the aftermarket ignition coils. Lots of bad press about them on this forum. They don't seem to last very long, compared to the original Diamond types from Japan which can last 20 years +. It would be wise to hang on to the old coils. If the bodies are not cracked, there's a good chance they are still good.

You could soak a little bolt loosener in the spark plug well, to get that last plug out. Don't neglect it. I don't think the new coil will appreciate that old worn-out spark plug!

 

Thanks again. The ones I purchased were new Lucas coils for which I paid £30.00 a unit. Thanks for the tip about the plug, I'll try that.

 

Hi. I got them from berkshirejagcomponents on ebay. Lucas coils, new, at £29.99 each. Seem to be fine but I have kept the old ones just in case.

 

Thanks Richard.