Malfunction when up to temperature.

[DavidMJS]

Help please! I have had my 1995 X300 Sovereign 3.2 from new and it has been remarkably reliable (98,000 miles from new). It has always been maintained by a Jaguar Specialist, but has been hardly used during this awful pandemic. It was serviced in November and was fine then. I have tried to keep things running by starting the engine up every week and moving the car around our drive. I recently left the engine running for rather longer, so well up to running temperature, and found that the engine would not rev above 1000 rpm. Tick-over is perfect, but you cannot rev the engine. I would normally take the car to my Jaguar Specialist to have it fixed, but dare not set out on the 13 mile drive! I do not maintain the car myself, so any ideas please? Many thanks.
David.

[PeterDavisX300]

Hi David

We'll need more information. When you say it won't rev above 1000rpm, is the accelerator pedal moving freely to the floor? Is the car starting to rev, then refusing to go any further even though the pedal is going to the floor? Does the car 'stutter' or miss-fire when you try to rev it? Did the car overheat whilst 'ticking-over'? With the bonnet open, can you see the movement of the throttle-cable on it's spindle?

My first port of call would be movement of throttle cable, and integrety of same. Then the butterfly at induction. Is the car in a garage or outside? Do basic checks, oil-level, coolant level, freedom of movement of pedals, and keep in touch, and if it's fixed let us know, and how it was fixed.

I'll check again tomorrow.

Peter.

[DavidMJS]

Thank you Peter for your response. I can start the car normally from cold and everything works as normally. The car accelerates up and down our drive without hesitation and will revs freely. It is only when the temperature gauge reaches the normal operating level (and after several minutes at this level) that the engine become lumpy. When stationary the tick-over is normal, but once you try to accelerate, the engine tries to speed up, but falters. If you persist, it will not go above 1000 rpm. It does cough and splutter and I think that there may be some smoke at the rear end. It has been so very windy lately and the car is outside at the moment. I sold my very rare 1976 Daimler Double Six Avon-Stevens Convertible in early December, but the new Custodian hasn't been able to collect it yet, so the X300 is outside. Wretched Covid19! I am assuming that the problem with the Jaguar is caused by a sensor which is sending the wrong information once the engine is at operating temperature? I checked the car out after my original post, having left it for an hour. it ran perfectly until it reached the operating temperature again. All very frustrating. I would welcome your comments. The only problem I have had with the car was when the "mass air flowmeter?" failed in 2017. This and an oxygen sensor were changed by my Specialist garage.

[cafcpete]

There are two temperature sensors on these cars.
One drives the gauge and the other tells the ecu what temperature it’s at, and therefor how much fuel to use.
If this second sensor is faulty the car will always over fuel once up to temp, and this might explane your problem.

If you get a ODB reader this would hopefully tell you what the reading is.

Peter

[steve_m]

I had exactly the same on a Subaru and a Freelander; it was the catalyst collapsing in the exhaust and blocking it.
Removed the cat and it was fine.
Obviously, if yours hasn't got a cat then that probably isn't the problem.

[PeterDavisX300]

There are two temperature sensors on these cars.
One drives the gauge and the other tells the ecu what temperature it’s at, and therefor how much fuel to use.
If this second sensor is faulty the car will always over fuel once up to temp, and this might explane your problem.

If you get a ODB reader this would hopefully tell you what the reading is.

Peter

Yep, I concur. Over-fueling, probably stuttering with dark smoke. You say you had work done by a dealer, don't always presume they fit genuine Jaguar parts, (even if they say they have!) You should get a reading from one of plug-in ELM 427 or OBD attached to a laptop. I have an i930 carsoft, but Im probably more than 500 miles North of you.

Let us know how you get on.

Peter

[DavidMJS]

Many thanks for all the useful comments for this very frustrating fault. I don't have any diagnostic kit because the car has always been serviced and cared for by the Main Dealer, or from 2003 by a Specialist Jaguar garage (who tends to "look after" the car, rather just follow the service sheet). The only car I still maintain myself is my Alvis Drophead coupé that I bought when I was at university in 1964! Anyway, back to the Jaguar. I started it up this morning again to try more diagnosis. It started immediately and ran normally for a minute or two, then as I opened the throttle, misfiring started at about 1800 rpm. Over the next few minutes this got progressively lower each time I tried and soon I was not able to go above 1000 rpm. The engine just "pops" and "bangs" and there is some smoke from the exhaust (but not black). Tick-over is still normal. I think my only option now is to try to get the car transported to my Specialist just outside Barnstaple. I will report further as the fault is cured. Once again, Many thanks,

David.

[davidr]

I'm wondering if its a fuel delivery problem? Maybe the fuel pump on the way out or a clogged filter?

[DavidMJS]

I can now report that the engine malfunction has been cured. The crank sensor was failing when hot and replacement has solved the problem. I gather that original Jaguar ones are no longer available, so we will see how long this one lasts. Thanks everyone for all your useful comments.

David.

[PeterDavisX300]

Hi David

Well, that's great the problem is solved, and even better that you reported back to us all what the problem was. I've had a failed crank sensor, but it just 'failed'. Working one moment, then not!

Peter.