Auid A3 engine problem

[maix27]

Hello folks,

Got a bit of an issue with my 97 A3 1.6. First my engine overheated and I found I had a blown (read destroyed) fuse box (the one on top of the battery) got that sorted but whilst sorting it i noticed an engine misfire and the occasional pop (coming back up the inlet pipe, not through exhaust).

I fitted new HT leads suspecting a poor spark; plugs were cleaned but were nearly new. Air filter is clear.

I plugged a reader in last night and pulled of a few error codes, rubbish ones except one telling me the upper Co2 reader on the Lambda sensor isn't reading (code: 00557)

I'm going to jack it up and clean the Lambda tonight.

I have two questions! One: anyone know the best way to get to the lambda on the A3, I can't see it from the bay.

Two: has anyone had similar problems, lack of power, pop on overrun and misfire on rising revs? Was it a lambda problem or MAF sensor, as I get the impression it's going to be that!

Thanks for any help in advance!

Mike