Alright - I have been on a month long journey to try and fix my early 1993 Jaguar XJS. It has the 4.0 AJ6.

The issue is that the car stalls when cold. It runs perfectly when warm, but when I start it up in the morning, and go to back out or pull forward the car will stall (in both forward and reverse). The moment the car warms up, it seems to run perfectly.

Now here is the confusing part, I have replaced so many parts in the last month, including

1. The ECT sensor
2. The Fuel Injectors
3. The TPS (dont even ask!)
4. The EGR valve
5. The Fuel Filter
6. Sparkplugs
7. Heated exhaust gas 02 Sensor



At this point, the only thing I havent replaced is the ECM. The ECT sensor connector was a bit dirty. I cleaned it, and it shows resistance. I also cleaned out most of the intake, but the car has 55k miles, and it basically looked new. Only thing I havent messed with the is the Mass Airflow sensor. The car runs strong when warm, shifts correctly, and cruises comfortably. The car does NOT stall in park or Neutral. Any advice would be helpful. Again, the car runs near perfect when warm. It only stalls when cold, and either in drive, or reverse. }

At this point, I am done digging into parts, hoping someone can help me logic through this (my current thought is the drive or reverse part is playing a role, and it is actually some signal from the transmission? The only issue, is that doesn't explain the cold only part). Other thought is that I need to reset the TPS (which actually means resetting the ECM)?

 

Jbaker229,

Have you correctly checked the autobox fluid level when hot? The ZF box / torque converter will often stall when cold if put in D or R if the fluid level is low.

Fully warm up the fluid, cycle the box through all positions a few times, holding each position for a few seconds (you may have to feather the throttle a bit if it's so low that it wants to stall). Then put it in Park, and quickly check the dipstick. It only reads properly on one side, so pull the stick, wipe it, replace it and pull again to check the fluid.

Paul

 

Got it. This actually makes a lot of sense as I sucked some fluid out about 6 months ago because the tranny was overfilled. Last I checked the transmission fluid level looked good, but will check. To be clear, the car is completely losing ignition / shutting off.

I might add a teeny bit of fluid to the tranny and see if that solves it.

What is odd, is the car will move in drive / reverse, then it will lose ignition. If you are on the gas, in either gear, while the car is cold, it runs just fine.

 

Don't add any fluid until you've really checked it properly. You really have to check these accurately when warm and cycle them through the positions.. There is absolutely no point checking the fluid level on that ZF box when it is cold. The level on the dipstick changes considerably when it is warm and cycled.

Cheers

Paul

 

Hi Paul,

I checked when the car was warm (like 99 degrees in Atlanta Georgia after a city drive warm), then cycling through all positions. Guess what? It was 3/4 of a quart low! Now I will have to wait until tomorrow for the car to cool down enough to test. Fingers crossed this is the issue. I think you are probably right. If only I had posted earlier! Would have saved me digging into the throttle body unnecessarily.

Thank you so much! Funny, cause the transmission was overfilled, and was shifting poorly about a year ago. Vacuumed up some fluid using my mighty vac. I thought I had the level perfect (Measured at correct temp, cycled gears, etc.) Guess I was off, I figure I didn't let the fluid settle and some was stuck in the dipstick tube? I will say, I always find reading transmission fluid levels annoying. Hard to tell what is residual and what is real, but I think I have it right now.

 

I don't know if it will cure the problem, but low ZF box level definitely causes an issue. It's easily done, don't feel too bad about it! I had a problem recently when I changed my fluid and precisely filled the amount I'd drained. But I'd underestimated how much it had been leaking through a dipstick corrosion problem, and it suddenly started wanting to stall when going to move off after being placed in Drive or Reverse at cold. I then accurately measured and I was 1.5 litres short!

The ZF box level really does change significantly as the fluid warms and moves around the system. It's a pain, but you really have to check using the hot procedure.

If it does cure it, at least it was a cheap fix!

Good luck

Paul

 

Hi Paul - thank you so much. Started the car yesterday after sitting overnight. PROBLEM SOLVED! Hopefully this helps others in the future.

 

Late lesson learned:
If you're having trouble when engine is cold, but not hot, most sensors can be ruled out, as the car has not yet gone into closed loop. Oxygen sensors, Coolant sensors....even TPS will not have any negative effects on a cold engine.

Injectors, fluids, plugs, coils and the ECU would be prime suspects....but you know that now.

Thank you for coming back to confirm the fix. It will undoubtedly help people in the future!