ECU warning light and spurious misfire - electrical problem?

[porterclough]

Hi,

I've got a strange recurring issue with my 2005 2.0 FSI A3.

Several times now in the last month the car has developed an apparent mis-fire, or possibly gone into limp mode, after an hour or 90 minutes driving.

The first time this happened a while ago on the motorway, had to pull over as as well as the engine light, EPC light, and traction control light coming on, power was reduced and wouldn't go over 40mph. Stopped the engine and restarted, light still on but ran fine and I drove home. Next day no warning lights and worked fine. Got a mate to plug his laptop in to get codes off a week or so later but no codes.

So, didn't worry too much. But then a few weeks before xmas it happened again, this time didn't seem to run properly after stop and restart. Called RAC expecting it may be an ignition coil problem. They were busy so sent a recovery truck instead of a mechanic. Got towed home, then in morning car still had engine light on but seemed to be running better. Called Audi, they said don't drive it. So called RAC again, they read codes and it said multiple random misfires. RAC guy wrote codes down and cleared codes, advised I drive it until it happened again to narrow down which coil it was.

So, a week driving around town and it was fine. Next motorway journey, happens again. Got to services in limp mode, still misfiring after stop and start. Called RAC. When they get there 30 mins later, engine fired properly. So RAC guy read codes, wrote then down and cleared codes. Drove home, but after a 10 miles, happened again - but this time after a couple of minutes on hard shoulder started up properly (warning light still on) and I got home.

Took to garage (local one, not Audi dealer), they read codes, replaced two ignition coils.

Drove round town for 2 weeks without problems. Then, motorway journey, did nearly 2 hours before misfire, had to pull over to hard shoulder. Turned engine off, restarted, ran fine but with ESP and engine and EPC light on. Stopped and started again, EPC light went off but engine light and ESP light still on. But running fine, drove home 40 miles with no problems.

Next day, no warning lights and running well around town.

I'm not sure what to do next. I can't keep taking it to the garage for them to replace ignition coils constantly - I suspect something electrical or electronic is wrong and the warnings are spurious, and the engine is going into limp mode in response to an incorrect sensor or something like that.

Has anyone any ideas how I could debug this?

cheers,
Chris.

Edit:

PS. Opinion of first RAC man - "It can't be the coil packs as it's running fine now"
Opinion of second RAC man - "It might be a crack on a coil that only becomes a problem when engine hot"
Opinion of mechanic at garage - "Funny things, ignition coils"

Anyway, if get to the point where I've replaced all four ignition coil packs, what next?

[porterclough]

Thought I should follow up in case anyone else is looking at this.

I found a couple of similar posts on other forums (I would post link but is that allowed?) where people had same or similar symptoms on VAG group FSI engines (various car models) and suggestions were:

1. Faulty air mass sensor (MAF)
2. Faulty throttle body / throttle potentiometer
3. Split in vacuum hose (not entirely sure what this means)
4. Faulty lambda (exhaust oxygen sensor)

Does this ring any bells with anyone? Why would these faults lead to various fault codes on the computer none very helpful? The really odd one is the ESP light coming on.

I'm wondering how best to tell if the problem is with the MAF sensor as opposed to the lambda sensor, for example.

If anyone can recommend someone good in the Sheffield area I'd be grateful.

[crisis72rdh]

Hi,

I have the same engine on my A3 which had the exact same problem. I spent hours looking online with many trips back to the dealer and it seems to be a specific problem on the 2.0 FSI (Non turbo) engine. I had my coil packs replaced 3 times in 2 months! All under warranty. After each time the car ran fine for a few weeks then started misfiring again, eventually the car went into permanent misfire/limp mode with black smoke at which point it had the EGR valve replaced.

This again was fine for a few weeks but started randomly misfiring for a second or two every now and then. The dealership took it in again and cleaned or replaced some of the engine management cables. The car hasn’t misfired since then going on about 7 months now, so fingers crossed its resolved. I have however since then needed a new catalytic converter and thermostat!

This particular engine model combination seems to be buggy, just google 'audi 2.0 fsi misfire' and you will find a few others with the same problem. I have read recently that VAG is doing some kind of unofficial recall on certain coil packs which they have acknowledged to be faulty - http://www.autocar.co.uk/forums/t/17883.aspx. Perhaps you should give your local dealership a ring to find out if you are eligible?