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Matt, Mechanical Engineer
Category: Jaguar
Satisfied Customers: 22765
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Ive a 2013 Jaguar XF 2.2L 200hp. I feel a distinct engine

Customer Question

I've a 2013 Jaguar XF 2.2L 200hp. I feel a distinct engine braking as my 2013 Jaguar XF decelerates from around 10mph to below 10 mph. I also feel and abrupt upshift if I'm driving at <10mph and step on the gas gently to increase speed. This problem occurs most of the time around 10-15mph but not all the time. Jaguar tell me this is a known driving characteristic - but I'm not convinced since it does not happen all the time and also did not occur on a couple of replacement vehicles that they gave me. Can this problem be fixed and will you be able to speak with the Jaguar engineers on my behalf?
Submitted: 4 years ago.
Category: Jaguar
Expert:  Matt replied 4 years ago.


This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.

if the engine condition is the same then chances are the meter or the connection to it is faulty

Air leaks are very temperature dependent as gaps can open or close up as things expand with heat, so the weather and engine temperature can effect them.

This leads them to be quite intermittent in the case of mild leaks

its also worth cleaning the airflow meter by removing it from the car and spraying the exposed sensor wires inside the tube with a brake or switch cleaner - ensure that the cleaner is one of the old fashioned, non Eco type that does not leave a residue

On no account touch the sensor wires with anything physical as they are extremely fragile

Customer: replied 4 years ago.

My car is brand new with only 3500 miles on it. Jaguar technical team is telling me that it is a characteristic of this car - which I find hard to believe.


If there is an air leak as you suspect - why do I feel the problem only at a very precise speed of 10mph? Also why is it that the error does not occur all the time?



Expert:  Matt replied 4 years ago.
Hello Kedar

if there is an airleak it effects the ECU's load measurement and this in turn gives poor control over gearshifts and give driveability issues as you describe

now its also possible that the issue is a software one but it sounds like when a new flash was tried it was good until the ECU re-learnt some values and re-introduced the problem

hence my suggestion

airleaks are usually very cheap and easy to fix so its well worth doing the test
Customer: replied 4 years ago.

ok Matt I will request Jaguar to carry out these tests and will send a feedback and rating as soon as I hear from Jaguar.



Expert:  Matt replied 4 years ago.
No problem

one other thing to ask about if if your car has the latest calibrations loaded into it for both the gearbox and the engine