Hi All, After finally getting my XJR back on the road and enjoying daily use for a few weeks it has developed a new issue!
I was driving along the motorway at steady speed when there was a jerk from the drive train and the transmission light came on, but it didn't seem to downshift to third which I believe is the default for transmission limp mode. I was able to continue to work where I checked the trans fluid level, it was hard to tell because there were some bubbles in it, but I thought it might be low so I added a small amount. Drove home with no problem.
A few days later It turned over but didn't start. I charged the battery in case the voltage was dropping too much for the electrics during cranking, and it started. I did notice a whirring / whistle from the front of the engine that I hadn't noticed before, which died down as I let it warm up. Then it stalled, as if the ignition had been turned off. It started again but took a few seconds of cranking. I held it at about 2k rpm and it seemed to be running fine, then the transmission light came on and the engine cut out again as if the ignition had been switched off.
The transmission light was followed by the oil pressure light as the engine slowed to a stop, but the other warning lights didn't come on.
I have previously had a random stalling issue that was cured by cleaning the contacts on the ECU plugs, so may start there, but other than that not sure where to start, so any ideas appreciated..........
Regards,
John

 

It's likely that the Transmission light is a red herring but you should get the codes read to be sure. The Trans light will come on if the engine stalls.

My primary suspects would be
1. Crankshaft Sensor
2. ECM Controlled relay
3. Poor earth or power connection between battery and engine bay (earth points and power +ve connections on bulkhead)

 

I think Brendan is right about the transmission light likely being brought on by the stall, and the crankshaft position sensor would be an excellent place to start.
As an aside, I have a hazy recollection of advice against revving in neutral for any length of time as transmission damage can ensue.

 

You can rev in neutral only if you haven’t shifted into gear. If you have shut the car off and wait a minute, stay below 3k

 

Thanks Guys,
I changed the crank position sensor a few years ago and it hasn't done that many miles since, but agree that the symptoms would match. I will try swapping the relay and see if it repeats. In terms of earth connections, do you think it is adequate to test for continuity, or is it a case of measuring a sufficiently low resistance between components individually rather than say between engine block and chassis? What could be considered reasonable/

 

It would be worth checking the electrical connector for the crank position sensor (CKPS). Because of its location it tends to become contaminated with oil and gunk. Also, just because the CKPS is only a few years old doesn't mean it hasn't failed. Some replacements have been known to fail prematurely. Since the CKPS is not terribly expensive and its failure modes can be sudden and difficult to diagnose, it's a good idea to carry a known good spare in your car for testing or emergencies.

Ideally you want 0.00 ohms to ground between every grounded component and the chassis, but realistically you're going to see 0.1 - 0.2 ohms on some ground wires due to the length of the conductor. Part of your regular tune-up maintenance should be cleaning all the ground points you can access in the engine bay (especially the ones referenced by the ECM), both ends of the engine ground strap, and the grounds in the trunk/boot, including the battery negative cable connection to the body.

I don't think this will be your problem, but it would be worth checking your transmission fluid level again, since low fluid has been associated with stalling (though usually while slowing to turn or stop). To get an accurate reading, drive the car for 15-20 minutes at speed to bring the fluid to full operating temperature. Park on a level surface and set the hand brake. With the engine running and the brake pedal depressed, move the gear selector through each gear position, holding each one for at least 3 seconds. This fills the valve body and other passages in the transmission with fluid. Return the lever to Park. Now check the fluid, wiping the dipstick and reinsterting until you get a clean line of fluid on the stick. The level should be right at the MAX or HOT line. Adjust as necessary.

Regarding transmission fluid, the original specification was Dexron III. General Motors eventually discontinued Dexron III and stated that Dexron VI was backward compatible, but it is not suitable for use in your ZF 4HP24 transmission because its viscosity is too low. In the U.S., a commonly-available Dexron III equivalent is Valvoline Dex/Merc (in the blue bottle, not the synthetic version in the red bottle, which is too thin). In the U.K., another option is Mobil 1 ATF, which is a high-quality synthetic Dexron III equivalent of appropriate (high) viscosity.

We'll be anxious to learn what diagnostic trouble codes are stored - they may offer a clue as to your stalling, unless its the CKPS or its connection, which typically won't trigger any codes.

P.S. Sorry for the long post. It's late and I'm too tired to edit it for brevity.

Cheers,

Don

 

Hi xalty,

My memory may be as hazy as countyjag's, but I seem to recall that a Jaguar TSB warned against revving the engine past 2,000 rpm even with the transmission in Park, due to a risk of damaging the torque converter. If you have a different reference I would be grateful if you could post it so I can add it to my library.

Cheers,

Don

 

2k is max allowable for extended periods. Here’s a BMW reference guide for dealing with high idle emissions testing. Damage caused is at the is at the front clutch packs.

BMW NA service bulletin # 24 01 91 (3196) dated June 1991

https://e-wiesinger.de/tipps/AU-Anweisung.jpg

 

xalty,

Thank you for posting those. They seem to agree with the Jaguar TSB I'm thinking of. I can't read the German TSB, but here are the relevant warnings from the English TSB from BMW:

Cheers,

Don

 

Thanks again, I need to find my OBD interface, it seems to have been tidied away, but will do as have seen codes before without the check engine light being on- and agree may be worth buying a new crank sensor to be sure. I had just started to get some confidence back in the car....

 

I think we all forgot that OP has an XJR so none of this applies to this car...

 

 

Yes, I meant to reply, it has the GM4L80e transmission, but guess it would be reasonable for similar advice to apply. I had assumed that if the engine was running, then fluid would be getting pumped around the transmission and cooling / lubricating it. but perhaps not.

 

Just to round off, it was the crank position sensor. On fitting an new on it fired on virtually the first turn of the engine and seems fine. From memory measuring the resistance, the old one was about 2.6 kOhms and the new one was about 1.6 kOhms, I might be wrong with the units, also the plug connector on the harness was damaged so I took the old sensor to an auto electrical factors called wood auto and they found a new Econoseal socket to fit for £4, so a job for this weekend. Hopefully reliability restored.