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Matt
Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 21624
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Audi A5 doesnt accelerate smoothly through 1600 to 2000 rpm.

Resolved Question:

Audi A5 doesn't accelerate smoothly through 1600 to 2000 rpm. Engine seem to misfire. If feels as though I've gone over a large bump in the road
Submitted: 2 years ago.
Category: Audi
Expert:  Matt replied 2 years ago.
Hi

can you tell me what engine size and fuel type this is please?

also when was it last serviced and how many miles has it done?
Customer: replied 2 years ago.

It's a 3litre Diesel A5 TDI Quattro. 163,500 miles on the clock. Last serviced at 160,500 miles. It's been serviced reguarly from new.

Expert:  Matt replied 2 years 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 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.

If this is OK then also check the connections to the EGR valve, if either the vacuum pipe of electrical connection are damaged / corroded then the EGR can be on all time which certainly will hurt performance.

Its also possible that its a fault with the EGR valve so its worth removing the valve and cleaning it out with brake cleaner, if it looks particularly clogged then replace it.

Matt and other Audi Specialists are ready to help you
Customer: replied 2 years ago.

Thanks Matt,

This makes sense, but I will need to go to an Audi specialist to get the work done. Is there anyone in the South London area that you would recommend?