2001 A4 1.8T Q Avant

Ran fine this morning, idled fine on restart, started misfiring when put it in gear. Misfire started w/o warning, blinking CEL. Plugs are less than 5k miles old.
Set these codes:
P0411 Secondary Air Injection System, Incorrect flow
P0171 System too lean
P0302 Cyl 2 misfire

So I cleared codes and swapped the Cyl 1 and 2 coil packs. Ran it a few minutes, idled fine but misfired under load (just up and down the driveway). The blinking CEL came back but the only new code was P0301, cylinder one misfire.

So I should just get a new single coil pack and install it and I should be good to go? Or do those other codes (which didn't come back on the retest) suggest something more to worry about? Do I need to run it longer before I make assumptions?
Thanks,
KW

 

Coil swap cured it, looks like. Weird to see a lean code with a misfire--I'd have expected rich if anything.

The 0411 and 0171 may have been set earlier, tho. I had a CEL a few weeks ago that went away, I thought it was a fuel tank lid thing and ignored it. But it came on during a serious cold snap (that"s why I thought I hadn't turned the gas cap down tight--it was bitter out there). But perhaps the SAI solenoid froze or something...

 

You're probably good to go for now. The coilpack swap sounds like it took care of it. When you saw the SAP code in there, and then cleared it and restarted the engine, it wouldn't have reset since the engine was already warmed up and the SAP only runs when the engine is cold. If you throw the SAI codes again in the future, you may want to start budgeting for a new pump, as it may well be starting to die. Glad it appears that the misfire code is fixed though.

 

Makes sense, thanks. The car has just over 100k miles on it now, so everything that hasn't been done already is suspect--but we've stayed on top of the maintenance by the book and it's just stuff that's going to age out on us.

 

I've had the Secondary Air Injection System incorrect flow code come up before and just let it slide for two years. One day out of the blue I decided to trouble shoot it and found that it was simply the fact that the vacuum hose that goes to the selonoid on the back of the head had broken and as a result had allowed condensation into the air injection pump and burned out the fuse. After replacing my vacuum hoses, purging the water from the pump and replacing the big fuse in the ecu box the system worked perfect and has been ever since.

 

I also recently noticed the engine missing which had progressively gotten worse. This last Monday it got bad enough that it set off the CEL which blinked initially then stayed on steady so I went to Checker and they let me borrow their code reader after I gave them my ID and found it to be the p0302 missfire cylinder 2 code. Just as a shot in the dark I bought a set of Autolite plugs for $8 and cleared the code. I went home installed the plugs and now she runs great no missing at all. I have never changed the plugs in the 4.5 years I've had the car and after taking them out, they were all looking pretty burned and the gaps were all wide at three of them near .060+ and one about .043

 

Bah. Stop buying SAI pumps and just take them out and tune them out. Unitronic will do it for 2001s. Saves some weight, too. All you need to buy is the SAI blockoff plate. Of course, getting a tune costs more than a SAI pump, but it's something you should be doing anyway.