I have a 96 A6 avant, 2.8l. It sat for about a week with no use. Started it on Sunday, idled VERY rough, I was shaking a bit in the driver seat. Car wouldrev sporatically, sputtering and popping. In the engine bay it sounded like jiffy pop when you got the engine to rev.

I got a VERY strong sulfer (exhaust) oder in the cabin. CEL was on, codes were misfire cyl 4&5, mass air flow, TB position sensor.

The car seemed to be chocking on its own exhaust as if the EGR was not letting the exhaust pass and too much was being directed back into the combustion chamber screwing up the mixture thereby causing misfires.

Any advice?

Thanks.

 

Check your scanner for the "egr monitor", to see if it is working. If the "monitor" is working, then it is not the egr.

 

A bad mass airflow sensor can cause cars to run like that and can cause cars to misfire. What I would try first is to get some MAF cleaner at your local parts store and clean your MAF sensor. If it runs better after that then you know that was the problem, if not you can go on the other two codes. The EGR valve wouldnt cause it to misfire as bad as you describe. The EGR valve is for emission control and can cause your car to idle rough but usually nothing too major. Id start with the MAF sensor and see how that goes.