My a4 is sick... several codes, need help
 

So I just replaced my cat thinking that would resolve the cel issue, but now I got these other codes -

p0300, p0303, p0304, p0420

random/multiple cylinder misfire, sporadic, cyl 3 and 4 sporadic misfire,

catalyst efficiency below threshold, bank 1 (that may have been fixed w/ the new cat)

any suggestions would be appreciated, thanks

Re: My a4 is sick... several codes, need help
 

02, 1.8, 99k, apr stage 1+, hfcat, borla exhaust... fyi

coilpack issue?
 

I replaced the coilpacks a little over a year ago, could they go bad already?

Yes they can, especially with more aggressive software. Looks like you need
 

coil packs 3 and 4 only based on the codes (P0303 and P0304). Those are the two towards the end closer to the battery.

here's the update...
 

so I went back to the dealership when the light came back on this afternoon and the same code 0420 (catalyst sytem bank1) was there... my dude said the sporadic misfires are the least of my worries and he thinks its the cat. (They did all this for free btw...)

If it is the cat, then I'm pissed cuz its brand new and I don't wanna pull that s.o.b. off again. I'm gonna call Labree Motorsports and see what they say. How could it be bad if brand new?

Free?? Do you have warranty still? Nice dealer!

nope, my dad had his 911 mods done by them (like 6 grand) so they hook me up now

Was it a new OEM cat or aftermarket?
 

There has been posts in the past where aftermarket cats often throw codes in our cars even though new. One of my local indy shops that work exclusively on Audi, Porsche and BMW has told me the same in the past. Go OEM cat if you can.

its a new hfc, i'm considering replacing the o2 sensors next

I disagree. I'd fix the misfires first with new plugs or coilpacks. I think
 

he wants to sell you a new $$$$ cat rather than cheapo coil packs ($25 each, DIY). My suggestion:

1) Move the coil packs around 12 > 34 and vv.
2) Clear all codes.
3) Drive and see what comes back. If the P03xx codes return in different places, fix the coil packs, clear the codes, and do it again.

Coil packs are a lot cheaper to fix than a cat or O2 sensors. Swapping them around is a free evaluation, too.