misfire help welcomed

[ajcruz]

Hey all, first post, just wanted to get some input on this before I go and start buying parts.

car had been running smooth, fast, explosive. around 2 weeks ago I started to notice it take a extra second or two to crank in the morning but thought nothing of it as I live up north and it’s pretty cold super early in the mornings. Earlier this week I went to start up the car to let warm up and went inside for 5-10min. i came back out and the car sounded a bit off , i got in and noticed a cel and epc light and the car shook hard. i proceeded to turn the car off and back on , cel stayed while epc light went away. I drove it down the drive way and the car was not driving great. could immediately tell it had bad misfires. Ordered new spark and coils as I wanted to replace them already and was finally able to do so today. car turned on immediately after being parked outside in the cold for 4 days. the car felt 10x better at idle than it did before but i still felt a little shake. also a very strong odor of fuel coming from the engine bay. scanned it and got this. Anyone have any experience with these? Car will continue to stay parked until fixed.

[P0302] Cyl. 2 misfire detected

[P1238] Cyl. 2 fuel injector -N31- open circuit

[P0420] Catalyst system, bank 1 efficiency below threshold

[P2442] Secondary Air Injection system switching valve stuck open, bank 2

[P130A] Hide Cylinder


2015 Audi S4

[SwankPeRFection]

Possible bad fuel injector on #2.

The CAT efficiency code on bank 1 could be a trickle down effect of a leaky injector and the ECU not being able to dial back enough fuel to keep it from running extremely rich (beyond the limits of the CAT exhaust gas cleaning. I’d fix the injector issue first before you jump to the conclusion that that bank’s CAT is blown out. It all depends on the timestamps as well.

The secondary air issue is just that, most likely clogged runners and probably needs a cleaning on both banks. Considering that will require uncoupling the exhaust to let the water out (if done per factory manual procedure) I’d have them scope the CATs at the same time to see if you need to replace them (if you’re worried about it). It’ll save on labor as they’ll already be in there.

[SwankPeRFection]

To retest everything since you did replace everything, you could run some injector cleaner and then clean all DTCs and see if and what codes come back.

[ajcruz]

I appreciate the input, I was able to find an injector from this volkswagen dealer in Texas for 200 and couldn’t pass up on it. They only had 2 in stock though, so I figured just the one for now and later down the road hopefully replace the rest as well or clean them all. Should arrive by next week so i’m able to hopefully fix that issue and move onto what’s next. Seeing this car parked knowing how fun it is to drive but I can’t is infuriating.

[S4'ed]

The Secondary Air Injection DTC code is because one of the switching valves, or the vacuum solenoid that control it, is bad. Clogged passages cause an "Insufficient Flow" type of DTC code.