Jaguar xf diesel - knock/pre-ignition at low speed

[anonymous-user]

I've noticed a few times that my Jaguar XF 2.2 diesel seems to have some knock at low speeds when I have the throttle barely open. The whole car jerks badly when this happens; opening the throttle slightly or closing it completely stops the knock.

Knock is just my interpretation of what is happening.

Any ideas what the issue is and what I need to do about it? Many thanks.

[reddiesel]

You dont say much about the age or the mileage of the car Mike , could it be something as simple as a mounting ?

[anonymous-user]

6 years. 80,000 miles. I don’t drive it hard.

Not sure what you mean by a mount. An engine mount do you mean?

It definitely feels like pre ignition due to the violent shake originating from the engine when it happens.

[anonymous-user]

I wondered if an injector was dirty or something

[reddiesel]

Well the engine and gearbox moves on its mountings under torque load and I was just wondering if you had stuck it on a ramp to have a look . The injector issue I have encountered before , if perhaps one injector is on the way out the uneven fuel meterage can throw the engine out of kilter sending a vibration up the drivetrain giving exactly the results you describe . Any Mobile Mechanic will be able to carry out a Diesel Leak Off Test and check the condition of the injectors , its a possible cause eliminated if nothing else .

[Simpo Two]

Manual or auto?

[anonymous-user]

Simpo Two said:

Manual or auto?

Automatic

[anonymous-user]

reddiesel said:

Well the engine and gearbox moves on its mountings under torque load and I was just wondering if you had stuck it on a ramp to have a look . The injector issue I have encountered before , if perhaps one injector is on the way out the uneven fuel meterage can throw the engine out of kilter sending a vibration up the drivetrain giving exactly the results you describe . Any Mobile Mechanic will be able to carry out a Diesel Leak Off Test and check the condition of the injectors , its a possible cause eliminated if nothing else .

Thanks for your thoughts. I was hoping a dose of some fuel additive might sort it! I guess I’ll need to get a pro to look at it.

[snafu10]

Try using this 4 Tec diesel cleaner have used their products for years about £15.00

[anonymous-user]

snafu10 said:

Try using this 4 Tec diesel cleaner have used their products for years about £15.00

TY I will give that a whirl.