Continuous Misfire

[tel200]

I have a 1997 A4 with 20 valve ADR petrol engine which misfires all the time ie on tick over and when revving. It drives rough. I have tried new plugs and leads, cambelt, 2 used coil packs, lambda sensor, hall sensor, airflow meter, fuel pressure regulator.

The compression test on no.1 cylinder is slightly down on the rest by about 5psi.

The camshaft timing marks are aligned correctly.

Its been on 2 diagnostic testers. 1 tester said it was a mechanical problem. 1 tester said it was airflow meter which I changed but it made no difference.

I do not know what to try next. Does anyone have any suggestions.

[yaman]

If you get it tested on VAG-COM and post the codes on here, we
will have a better idea.

Regards
Jim

[bannedbiker]

I had a similar problem with mine which was the TPS. Like yaman said though, find out the fault codes and post them here, these guys know their stuff!(Not me, I aint got a clue, but everyone else seems pretty clever...!)

[rhencullen1989]

Have you got separate coil packs for each cylinder? try to determine which cylinder is at fault, removing the coil wiring one at a time if it runs rougher then that coil is ok, when you remove one and there is no difference, then thats the faulty one.

My 1.8T AEB was misfiring on cylinder 2 and turned out to be the ignition amplifier, this is bolted to the top of the air filter and has an electrical plug on both sides of it. There is a way to check this, try doing a search.

[Quattros]

just to mention, check the exhaust system for blockages, easest thing to do is remove lambda sensor, and see if the exhaust gas can escape, if you have a partial blocked cat/exhaust it would mis-fire throughout all rmps.

[tel200]

Just to let you know that the fault turned out to be a blocked fuel injector. Runs fine now. Thanks to all for your suggestions.

[yaman]

That's a good result, did you have to get a new injector
or clear it with a fuel additive?

Regards
Jim

[tel200]

It was a used one I got from a breakers yard. We had tried everything we could think of and been disappointed and this was the last thing we could think to try before we gave up. It was almost a half hearted attempt as I was pretty much convinced we would never solve it. But boy did it feel good when it worked! I didn't realise a fuel additive could clear it.