chopsaw84

Howdy, my first post...

On my 98 A8 4.2 I started getting a misfire, so I pulled codes, cylinder #4...

I swapped coils with #2, still getting misfire on #4... Okay.

Swapped out spark plug with a new one just in case, still a misfire on #4. Plug looked fine.

Fine, I'll swap the ignition modules (amplifiers), did that and sure enough the misfire jumped to a new cylinder. Cylinder #3...

I swapped them back to verify and sure enough it goes back to misfiring on #4.

I expected the misfire to swap banks so now I'm not sure what's going on. Am I missing something?

I'll also add that sometimes I'll start it and everything fires fine, no codes or problems all day, makes me think I fixed it but it comes back the next day, no correlation to outside temp or engine hot/cold.

I'm new to Audi's but familiar with engines otherwise. Am I correct in understanding that the passenger bank is 1-4 front to back and the driver side is 5-8 and that the ignition modules service either one bank or the other, right?

Also, is the top module the 1-4 or the 5-8?

Any help would be appreciated..., I think I can slog through this and figure it out eventually but if anyone has some experience to share that can save me some time and money or could point out something newbie I'm doing wrong that would be great.

--James

I did like the fact that swapping things around on the Audi is very easy and doesn't require being double-jointed.

Prospeeder

obviously thats what is bad. The power stages DO NOT go bank 1 bank 2, Its like 1357 on one and 2468 on the other. which would explain why it goes from 4 to 3 when you change it. There on the same portion of the circuit in the powerstage thats failed.

chopsaw84

Thanks!

That clears that up,

I'm not sure where I read (or maybe I jumped on my own) that the modules were bank specific.

Any opinions on quality of aftermarket replacements...?

Again, thanks...

danielellis

I am having the same type issue. Where do I locate the ignition modules (amplifiers)? I swapped coil packs and still get the miss on the same cylinder.

chopsaw84

The amplifiers (on my 98 A8) are located under a plastic cover that swings open, it's located right in back of the airbox on the passenger side. The amplifiers themselves are right next to the fill for the windshield washer fluid stacked on top of each other.


The top module sends ignition signals to coils 1,4,6 & 7.

The lower one is for coils 2,3,5 & 8. (so I've been told).

Good luck, I replaced mine with a $28 unit off of E-bay and it's been working well so far.