My car after a trip to audi service for a different cel(O2 sensors + lean) is throwing up another cel. This time its for a misfire in cylinder 4 & secondary air pump.

Now i have the one heat range colder copper plugs in and they were at the end of their 5000 miles, i tossed the stock plugs in to hold me over until getting new ones. Either way the car runs rougher than normal, nothing significant, but noticable. I have not repulled the code to see if its still cyl 4, but clearly i am thinking its a coil pack that is going, is this right?

As for the secondary air pump, wtf....seriously not sure what it does in these cars anymore, i know what its purpose was in older cars, but can it really need replacing/be faulty?

2002 a4 94k, apr chipped stage 1+, bosch injectors, copper plugs.

Thanks guys

 

Secondary air pump runs at startup and helps pre-heat the catalyst to cut down on startup emissions. I'm dealing with the same issue on my 02 3.0. Had the pump replaced and the CEL went away for about 60 days or so, now its back. Pump tests ok so I'm thinking vacuum, electrical or an actual clog in one of the tubes that feeds the pump or goes from the pump to the car.

I also had a misfire problem that went away when I changed out my plugs, car ran significantly smoother after I swapped them out too.

 

I had the secondary air pump code, it was a vacuum line that connects the valve covers had a leak. I also had some of the little vacuum lines that need replacement.

 

when i went in for the lean code they did a vacuum test and everything was all sealed up. They had issues diagnosing so they made double sure there was no vacuum leaks.