Engine cutting out

[Henry9090]

Hi
I've a 2005 A4 B7 1600 petrol. ALZ Engine.

The engine has started cutting out. I'd be driving along and power would disappear for sometimes a few seconds and come back. Other times it stops for maybe 30 or 40 seconds whereby I need to stop and after turning it over on the starter for a while it starts again.

There is nothing very useful being reported by the ECU. The light came on and it was complaining about inefficient catalytic converter. I think this means that when it's not working it's still injecting petrol but it's not being burnt. Also, when it's in power down mode it occasionally backfires with a large bang, again suggesting fuel flow is OK (agreed??).

I replaced the ignition coil pack about 6 months ago and I'm starting to think it maybe has gone intermittent. This pack has two coils inside - each driving two plugs. I would have thought that if a coil was gone then two cylinders would still run, but in this case all cylinders stop firing. Maybe the pack has gone faulty in a part of the circuit common to both coils?

Also - if a coil was faulty then would the ECU detect that or not? I would have thought the ECU could have given more information.

Any ideas anyone? Should I replace the coil pack again?

[Henry9090]

Well, not much response so far!

I have now caught the failure using a VAG-COM log. See the attached log. It cuts out at around timestamp 417 and comes back around timestamp 440.

While the engine was dead the ECU was still trying to inject petrol (Inj. On Time). The ignition timing, according to the ECU, looked fine. The ECU appears to think everything is fine, even though it is not firing. I think if there was a sensor failure the ECU would likely stop injecting petrol.

Therefore I am about to invest in a new coil pack.:nervous:

If you think that's a bad idea let me know - quick!

I'll update in a few days with the result.

[Henry9090]

Well, the new coil did the trick.

So, the last coil that was installed lasted about 4 months. When I got it out there was no manufacturer marked on it. Looking at the web, there are a lot of these coils coming in from unknown manufacturers in China and I would guess I got one. I have been assured my new one is a Bosch, costing about £30 more than a Chinese job.

So, the lesson learned is to buy decent stuff and avoid unknown Chinese brands.

[VAGMAN54]

:buttkick: thats for being naughty,remember the forum is here to help and its peoples spare time that make it helpfull being sarcastic wont get you more help ,and you sorted it anyway :aargh4: