My A4 B5 is not firing on cylinder no. 1

[FrenchAudi]

It's been very hot here the last couple of days. It reached 40C on Tuesday when we drove down to Figueres in Spain, the last hour on motorways cruising around 130 kph.
The motor was running perfectly, but on arriving in Figueres we stopped for a coffee for about 15 minutes, and when I started the engine it was misfiring.
By disconnecting the coil packs one by one I found the fault was on cyl no.1.
A garage I went to insisted on replacing all 4 plugs and coil packs despite my asking them to just check no.1.
After this it was still misfiring, so they replaced the original plugs and coil packs and I left, as they were too busy to do any more.

Later I left the car twice in cool underground parks for an hour or so, and it didn't misfire when I started it again, but the misfire returned when I stopped and restarted after a short time, when the engine had not cooled down..
This suggests to me that a component is overheating somewhere, possibly inside the ECU.

Back home this afternoon I pulled no.1 plug and coil pack, put a spare plug in the hole, reconnected the coil pack and ran a wire from the coil pack contact to the plug laying on the cylinder head. There was no spark at the plug.

I don't think it can be a bad coil pack or plug, as replacing these made no difference, nor a broken wire, as the engine ran on all 4 pots twice after cooling down.

I think the fault must be in the ECU. Any other suggestions please?

Any recommendations for ECU repair??

[FrenchAudi]

I just started the engine after it had cooled down overnight. No.1 cylinder is still misfiring, so the problem is now no longer intermittent.

[Noony]

Have you had fault codes read via OBDII port?

[Crasher]

Running a coil pack in open air can damage it, start with a code read.

[FrenchAudi]

Thanks for the replies. There is a lot to do now we're back. I will check for fault codes this afternoon.

[FrenchAudi]

I just ran the Automatic test sequence on my VAG 1552 tester, which is contemporary with the car.

There were only two faults stored, both on Engine Electronics. They were 00575, "Intake manifold control pressure not reached", and 01249, "Cylinder 1 injector output open".

I'm not sure of the relevance of 00575, I have seen it once before and ignored it. 01249 was stored because I disconnected the plug on no 1 injector so that it didn't waste petrol when driving back from Spain.

I erased the fault memory, reconnected the injector, and ran the engine for a few minutes. The faults did not reappear.

Incidentally it is still not firing on no.1 cylinder.

I am about to remove the shields below the windscreen so I can access the ECU to get its details.

VIN is WAUZZZ 8DZ TA234305 8D5 OHA 1437495

[FrenchAudi]

That's about how long it took to remove the wipers, plenum cover, and ECU cover to get its details.

This is my ECU:

ECU.jpg

Can anyone recommend someone in UK who can repair it as necessary, and tell me if there are any problems involved in removing and replacing:-

1) The same ECU after repair?
2) A replacement 2nd hand ECU?
3) A new ECU?

The only ECU I have replaced was the one in my VW T25, which doesn't care where its ECU came from, so I carry a spare which has been tested in the vehicle.

[Crasher]

All ECU repair companies are charlatans… new it has been obsolete for ten years this month and Audi Tradition don’t have any.

[FrenchAudi]

I just checked the ECU signals at the coil pack connectors with an LED probe.

No.1 - no signal. The others are OK.

So 99% sure it's the ECU. Surely someone can fix a faulty component?

[FrenchAudi]

All ECU repair companies are charlatans… new it has been obsolete for ten years this month and Audi Tradition don’t have any.

So far I can't comment on that statement, as only one French company responded to my enquiries, and they said they can work on ECU's only through a garage, as they can affect safety. I'm guessing they have had problems with customers making faulty installations and have to protect themselves.

I also have a suspicion that many "repairers" clone second hand units to the failed ones rather than actually repair them.

Only one UK repairer responded, but he's so busy it took him 5 days to do so.

Maybe just as well I didn't send it off, as I just discovered that some or all versions of the A4 Avant with AEB engines, around 1996, have an extra component, N122, between the ECU and the ignition coil packs. It's variously called the Ignition Amplifier/Power Output Stage/Ignition Control Unit/Igniter, Audi no. 4D0 905 On later cars this was incorporated into the coil packs. My car has this component.

Apparently it is prone to failure. It is mounted on a finned aluminium heat sink on top of the air inlet so that the fins are in the air stream, so it obviously gets hot. That might explain why it failed when I stopped for coffee after an hour on the motorway in Spain with the temperature around 45C, and it no longer had fresh air going over it. Surprising that only one out of its four channels failed.

Amazingly, I also found my Bentley manual for the A4 has instructions on how to make an LED test probe for the ignition and injection signals from the ECU. It's just a single LED with a 330 ohm resistor in series, so I'm looking for bits to make it up.

Pencil probes with LED's are easily available, but I feel safer using the resistance value in the manual when checking the ECU outputs.

I have also ordered the component from Auto***, who had by far the best prices, and who have my car listed correctly with the correct parts for my VIN.

Prices range from €25 to around €100 for Febi etc. I ordered Vemo, a reasonable brand, at €45.

If the problem does turn out to be in the ECU I may be looking at getting another car. At least we still have the Alfa running and serviced up to date. The VW is still waiting for its new engine to be installed.