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Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 20384
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Volvo V40: HiI have a 2006 Volvo 2.0 V40 and Im having

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I have a 2006 Volvo 2.0 V40 and I'm having a problem with acceleration as I go through the gears. Once up to speed it goes perfectly. I've had the spark plugs changed and the fuel filter but it still does it. Some days are worse than others. The car is also using oil. Please help!!

Hello Janine

when you say you've having trouble accelerating - does the car stumble / stutter when you press the accelerator?

also does it idle smoothly or is the idle speed up and down ?
Customer: replied 3 years ago.

Hi Mat


Yes it does stumble/stutter and it doesn't idle too smoothly.


Regards, Janine

Hello Janine

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 cleaning out the throttle body as well as these move back and forth to control idle speed a nd can get gummed up - if you pop the intake pipe off and use a rage with some brake cleaner this is pretty effective .

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
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