Hi, I own an Audi A4 B7 2006 2.0T Quattro and my car had been misfiring for about over a week so I thought. Ended up being something wrong with my MAF (mass airflow sensor). I bought a dealers sensor and changed it and my car still has problems running it sounds as if it's coughing. Whenever I step on the gas to accelerate it doesn't. Also my check engine light has been on so I went into auto zone and I got the codes.

P0303 - Cylinder 3 MisFire Detected
P0089 - Fuel Pressure Regulator 1 Performance
P0299 - Turbocharged/Supercharged Underboost

i have no frickej idea what it wrong with it and what I need to change on this car. I was told it could be something with the whole fuel system or something like that. But, currently I'm running out of options and I don't know what to do. Please help me?

 

Check the cam follower first. Failure there has been known to cause several of these codes. If that's good, P0303 could be something as simple as a bad coil pack. Swap it with another cyl and see if the problem moves. You can do the same with a spark plug (or just replace all 4). I would say the P0089 is likely the low pressure fuel pump (had this with mine).

P0299 - that one could be worse. Anything from the diverter valve (if you still have the old style) to a bad wastegate/turbo. Try to solve the other two first and work from there.

 

If you haven't changed the diverter valve I would start there. It is inexpensive and not to difficult to swap out. I got the P0299 when mine went. Do what King states and check/replace the cam follower. If that thing wears through it can cause major damage.