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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22750
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a vw golf mark 6 fitted with a 1.6 tdi engine and dsg

Customer Question

I have a vw golf mark 6 fitted with a 1.6 tdi engine and dsg gearbox.
For the past two weeks when I start the engine it is impossible to rev it much over 20002200 revs in neutral, and even then it feels breathless and has to build up to these max revs. However, when driving it seems to operate normally..
I am shortly about to undertake a trip of several thousand miles and would not like an unpleasant surprise en route...
What do you think the problem may be? And what should I have my garage check?
Many thanks.. K
Submitted: 3 years ago.
Category: Car
Expert:  Matt replied 3 years ago.

if the car seems to drive normally then this may be an issue with the transmisson not allowing high revs in neutral

if there's no check engine or other fault light and the car accelerates well then I'd do check of all fluids and also check for 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