i have an 03 audi a6 2.7t i have replaced all the coils and spark plugs. and the vavle cover gasket on the drivers side . all parts from the dealership. but i still have a misfire is cyclender 6 and sometimes 5. what else could be causing it.

 

Did you have misfires on 5 and 6 before the recent service or is this a new issue after the service was done?

Is it misfiring at idle only / under load only / or all the time?

Are you sure the correct plugs were installed? FYI the plugs are factory gapped and attempting to change the gap can damage the tip.

 

Just like K04 said, make sure that the gap is what the factory gap is. You can buy cheap spacers to measure the gap at any local automotive store. Smoothly bend the tip of the spark plug to change the spacing in between.

 

Factory Spark Plugs for the 2.7T should not need to be re-gapped as they are correctly gapped at the factory. Checking the gap to ensure all six plugs have the same gap prior to installation is a good idea. Caution as the electrode tip can be easily damaged on the OEM plugs if one tries adjusting the gap manually.

 

What's the mileage on the car? Could also be the Ignition Control Modules. There are 2. Swap them and see if the misses move from one bank of cylinders to the other...if it does, I'll bet it's an ICM.

ICM Link