I am trying to help a friend with troubleshooting his misfiring car.
It is a 2004 A4 1.8T

The engine is shaking, obviously misfiring/not running on all cylinders.

I immediately found a whistle from the diverter valve (putting finger on the crack/hole makes the whistle disappear but does not change engine shake).

Scan log below.

He says the issue occurred right after he ran the gas tank dry and filled up (93 octane).

Any suggestions?

I suggested to:

- pull all plugs and see how they look like
- pull one coil pack at a time until one is found that does NOT change engine shake

Misfire is shown on 3 cylinders, but can't be that all 3 are not running. Engine shake feels more like running on 3 cylinders.

Could the bad DV valve cause misfires?

Any other suggestions?

 

is his mil light flashing if it is then its the coils. If its not then i would guess vac leak.

 

You probably have one bad coil, its causing several misfires. This is what you do, erase all the codes, start the car up and scan it again. It should immediately give you the cylinder thats misfiring before the other cylinders start to register. Then you can swap that coil to a different cylinder to verify its the coils. I would replace all of the ignition coils with bolt down Hitachis if thats the case.