S4 b7 misfire on Bank 1 2 and 3

Hi I’ve seem to have a strange issue I’ve had a few issues with my car my fan control module was faulty and kept killing my battery, since sorting that problem out my car now has a misfire on bank 12 and 3 I’ve changed the coils plugs and injectors done a compression test and all okay there plugged it to 3 machines and vagcom but nothing has come up can anyone shine any light on this

You say nothing came up with Vagcom but do you mean nothing besides the misfire codes? 1, 2, 3 are all on the right bank so check the wiring harness going to that side for a start. 4.2 V8 right?

Yes thats the only thing that came up was the misfire, I’ve had people look at and nothing apart from that is coming up very strange it runs fine when the car is moving its just on idle

Did you try to move the injectrs. Sometimes the injectors an cause issues. You said compression was ok does the car still have cats

Justincredible yea I’ve moved injectors around but no change, yea I still have cats on the car, I’m going to replace the fuel filter as the misses ran out of fuel in the car its driving me mad I’ve had 3 people look at it 1 vw specialist and no one can find a fault

Try punching out the cats. They might be bad. Missfires are generally a sign of bad cats on these cars. If you’ve moved the injectors/ plugs and packs. I would say that part is out of the way.

You can also pull the valve cover just to make sure there isn’t a lifter issue.

I agree with justincredible on checking the Cats. Don’t remember on the B7 S4 if it is easier to bump them from the top or bottom. Maybe a wooden dowel if you can’t hit it with a rubber mallet and see if you hear a secondary rattle. Injectors is also another possibility. How many miles on the car? Do you have Vagcom available? If so check the Cam phase timing. I think you want Blocks 91, 92, & 93.

When you say punch cats though do u mean make a hole? Cars on 80k miles I’ve swapped injectors around and the fault stayed in the same place

Just remove the cats. If the car sits for a long time you can also get misfires from the lifters bleeding down.

The car hasn’t sat there I had an issue with the fan control module and coz my battery was dead I didn’t stop for fuel my Mechanic came over and looked at it and it ran out of fuel I filled it back up and added redex and then the misfire started don’t know if it could be due to redex or the fan control module

you can always just unplug the fan control module and I doubt it would be that. I don’t know what redex is or why you would add it.

I’ve done that to the fan module and redex is a petrol cleaner or so it says I added as I ran out of fuel and thought it would be a good idea to clean the system out