Spark plugs were replaced 30,000 miles ago; there is no missing after initial cold start and warm-up period of about 20-30 seconds. Once the car idles down the engine vibration disappears and the engine runs smoothly, accelerates fine and the check engine light does not come back on if reset after initial cold start. All 4 coils were replaced by VW under recall so they are brand new.
I have researched and am wondering if the MAF sensor could be the problem.
Plugs are factory and were installed at the VW dealership. I don't think it is the plug or it would run rough even when engine warmed up.
If not the coil and not the plug causing the misfire on cylinder 4 when cold start, then what else upstream can be checked? Is there a fuel temperature sensor on the engine that might be bad?
No, I cannot read fuel trim values with my Diag tool. High pressure fuel pump was replaced 3-4 months ago by VW so that is probably not the problem.
The car idles roughly for the first 30 seconds during cold start only. After the engine idles down, the check engine light comes on with the P0304 code engine misfire. This message is always related to cylinder 4. What could cause this if spark plug and coil are good on cylinder 4? Is there an ICM (Ignition control module) on this engine? They had problems with the ICM on the 1.8T engine.