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Matt, Mechanical Engineer
Category: Jaguar
Satisfied Customers: 20384
Experience:  BEng hons Mech engineering, in auto industry 22 years
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After using cruise control periods in one stretch

Customer Question

Hi- after using cruise control for longer periods in one stretch (20 mins+) on my 2010 XKR, the automatic gearbox seems to be affected and the car doesn't run smoothly but almost bounces along. Any ideas what causes this and what needs to be done to fix it please? is it a common problem? Many thanks!
Submitted: 1 year ago.
Category: Jaguar
Expert:  Shantal-Mod replied 1 year ago.
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Expert:  Matt replied 1 year ago.
Hello 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.the signal is the main load input for the ECU and so has a strong effect on how the ECU calculates torque and controls the transmissionAs 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. I think its likely only to be a small leak as 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
Expert:  Matt replied 1 year ago.

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