Boght my son a used 04 A6 2.7t Quattro sedan for $3200. The other day after he drove a short distance (3mi) he went in store and back out (15min) and car wouldn't start. I arrived after 45min and pulled fuel relay and replaced and still took about 10 second crank before starting at rough idle. Stepped on fuel to clear it out and it was good. Idled fine and he drove home. Today he calls and says it idled at 1200 rpm at start up then dropped to 900rpm. Usually idles at 750rpm. Someone told us cps was bad. Light in dash on since purchase. I am now understanding that there are 2 sensors? Can anyone give advice on this matter. Thanks

 

Pull codes, that is step #1 then you can action from there

 

Ok. Pulled codes at O'Reilly's and only thing showing is coolant temp sensor high voltage. Engine light on in dash. Smells of raw fuel when it does this as well. Left my son sitting twice yesterday and late for work.