EPC warning light, shaking and misfires on VW and Audi

Which cars and engines are affected?

Volkswagen, Audi, SEAT and Škoda petrol cars with TSI and TFSI engines. EPC is the Volkswagen Group’s own name for this warning light. For other work on these cars, see our Audi and VW specialist page.

What are the symptoms?

Owners describe:

• the EPC light, often with the engine warning light
• the car shaking when accelerating

The EPC light can also come on with a gearbox warning on cars with a DSG or S tronic gearbox, sometimes with only some gears available.

When you book, tell us which lights are on, when the shaking happens (from cold, under load, at idle) and whether the gearbox feels different.

What causes it?

The EPC light is a warning, not a diagnosis. Faults that can sit behind it on these cars include:

• A misfire on one or more cylinders. The engine shakes because a cylinder is not firing properly.
• A stretched timing chain on the 1.4 TSI and on some 1.2 three-cylinder petrol engines. As the chain wears and lengthens, the tensioner over-extends and the valve timing moves, which can bring misfire codes, reduced power and stalling at junctions.
• Carbon build-up on the inlet valves of direct-injection engines, which can cause rough idle, slight loss of power and duller response. See our intake carbon cleaning page.
• A gearbox fault on DSG and S tronic cars, where the EPC light comes on with the gearbox warning.

How do you confirm the fault before fitting parts?

A fault code is not a repair, and a misfire code tells you which cylinder, not why. Before we quote for any parts, we:

• read the fault memory in the engine and gearbox control units with our diagnostic equipment
• read the misfire data for each cylinder
• test the ignition coils, spark plugs and injectors on the cylinders concerned
• if timing chain wear is possible, read the intake manifold pressure at idle and check the static valve timing
• if carbon build-up is suspected, inspect the inlet valves

We then show you what we found and send a written price. No part is fitted until you give your written approval.

What does the repair involve?

We replace or repair only the part the tests prove faulty. That might be a coil, a set of plugs or an injector. If the tests point to the timing chain, we quote for a complete kit with the chain, an improved tensioner, guides and sprockets, not just the chain. If the inlet valves are carboned up, we clean the intake ports and valves.

Once the work is done, we clear the fault memory, check that the misfire has gone and verify the repair, including a road test where appropriate.

How long does an EPC or misfire repair take?

It depends on what the tests find. Replacing a coil is a very different job from a timing chain.

Before any work starts, you get a written price and a promised time for your next update. If the car needs to stay with us, ask about a courtesy car when you book.

Is there a recall for the EPC light or misfires?

Whether a recall applies depends on the individual car, so check your registration on gov.uk. Recall work is done by the manufacturer’s network, not by us.