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Matt
Matt, Engineer - BEng Hons
Category: Porsche
Satisfied Customers: 20590
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Porsche Cayenne S: Matt I have a 2009 porsche Cayenne that

Customer Question

Hi Matt I have a 2009 porsche Cayenne that I seem to be having hard time with. I have to put my car in neutral to avoid the hiccuping or bubbling feeling thar it get. I did bring my car in for service and air filter, spark plugs changed and it's still there. Any suggestions?
Submitted: 1 year ago.
Category: Porsche
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.As its amechanical fault it tends not to turn on the fault light and you can sometimeshear a 'hissing' noise with the engine running. Check the hoseclips 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 yourleak.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 sparkto 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 oflighter gas to provide a spraying 'wand' and allow a direct blast of gas intoeach 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 beworth 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 worthcleaning the airflow meter by removing it from the car and spraying the exposedsensor wires inside the tube with a brake or switch cleaner - ensure that thecleaner is one of the old fashioned, non Eco type that does not leave a residue On no accounttouch the sensor wires with anything physical as they are extremely fragile
Expert:  Matt replied 1 year ago.
Hi
do you still need help?
Customer: replied 1 year ago.
Hi thereI will be talking to my mechanic on Monday about your suggestion. Hopefully he can do something
Expert:  Matt replied 1 year ago.
Understood good luck
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Expert:  Matt replied 1 year ago.
hi do you still need help?

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