2.0 TFSI Occasional Misfires on Partial Load

[lafa3ro]

Hi,

I recently monitored the misfires on my 2012 A3 2.0 DSG (stock) with OBDEleven just out of curiosity. To my surprise I noticed that every now and then, I'm seeing random misfires under partial load. I've seen those on the highway (cruise control active) or normal roads wit cruise control off. Nothing when idling, nor under heavy load from my tests. They occur on every cylinders, randomly. I did 2 run of about an hour each and got around 10 misfires per run.

What should I look for? Could these be considered normal in any way? I'm planning to go stage 1 sometime this summer, is this something that should be fixed before?

Thanks!

 

[samuelh_888]

There is a about 5 posts currently active re misfires at the moment. Have a read of them but consider looking at your plugs, coils, fuel filter, injectors.

No point tuning with a known misfire issue.

 

[lafa3ro]

I read the other ones but felt like it didn't relate much since the condition under which it happens for me seemed different. I think my fuel filter is quite old and wanted to replace it so I might start with that. Dont see how plugs, coils or injectors would go at the same time though, since I have misfires on every cylinders. Thanks for the tip on tuning, looks like I'll have to postpone that until it gets fixed then.

 

[Daveyonthemove]

I don't think the fuel filter is part of any of the service schedule, so it will probably help things if it is changed.
I bought my car last April and booked it in for a cambelt change and asked the garage to change the fuel filter at the same time.
According the the mechanic, the filter was fitted at factory and my car had covered 104k miles!
Needless to say, it felt more responsive on the drive home.

 

[samuelh_888]

I read the other ones but felt like it didn't relate much since the condition under which it happens for me seemed different. I think my fuel filter is quite old and wanted to replace it so I might start with that. Dont see how plugs, coils or injectors would go at the same time though, since I have misfires on every cylinders. Thanks for the tip on tuning, looks like I'll have to postpone that until it gets fixed then.

Plugs, coils and injectors won’t necessarily go at the same time but the plugs and coils is the cheapest place to start and a DIY job. If your coils are factory originals then they are 7 years old. Not old in the scheme of things but if one is starting to pack up then the others may or may not follow. You may as well replace all together and keep the others as spare. Plugs, if they have never been changed then will be due, they are only about £30/set.

If this doesn’t resolve the issue then maybe look at getting the injectors cleaned. R-Tech do this (at the time of mapping) and worth the additional charge. My car had a slight miss which was down to a reduced spray on one of the injectors. My injector couldn’t be revived so a new one fitted.

 

[lafa3ro]

Plugs are about 1.5 years old (16k km) but coils I honestly have no idea. In wanted to replace them before the tune anyway so that would be a good idea to try that too. Injectors were supposedly fine last year when I had the valves cleaned (by a Audi dealership) so I'll keep that for later.

I did charts of live data with OBDEleven to find scenarios under which the misfires would happen, I looked at RPM, engine load and misfire counters on every cylinder. Is there any other readings I could monitor alongside the misfire counters to possibly help pointing to the source of the problem?

 

[Daveyonthemove]

Check airflow just in case it's getting a false reading and that's causing the ECU to alter fuelling.
Might not give you much, but it might rule out the MAF.