O2 sensor or MAF? VAGCOM xls linked

[NickMartin]

Hi All,

My car is really really sick at the moment.

Ive run VAG COM on it, and only fault codes are for the n495 and the dumpvalve. But ive had these for a while and she was running ok - gonna get those sorted later on...

Anyhoo... She is now running very very slow & lumpy, almost stalling on idle sometimes...
Ive logged several 3rd gear runs and put them in the following spreadsheet....

Could someone please confirm with that either the O2 sensor is knackered - or the MAF is knackered (100g/s for a 180bhp 20vt seams low?) which is causing the odd O2 sensor readings.

When i unplug the maf she is better, but not anywhere as smooth or powerful as she should be.. All runs in the linked spreadsheet are with the MAF connected. Ive formatted and removed crap data to make it easier to follow...

http://www.computervisions.co.uk/vagcom.xls

Many many thanks NM.

 

[Martyn]

Dude, fix the leaks/issues firstly then re-log in 4th gear.

100g/s is low, you should be seeing about 135-140g/s, if the readings are still low after fixing the issues and re-logging you'll probably need a new MAF.

 

[NickMartin]

Ok

Gonna take it to my mates audi garage later and we're gonna replace n495 and dv. Will log a few runs and see how she behaves... We're thinking that a faulty n495 is really leaking boost - as a st. 20v 1.8 lump produces 125bhp max, which is what mines giving me.... Would also explain maf and O2 stuff....

Is a 4th gear run better than a 3rd? 3rd @ 6k is much more practical on these roads than 4th @ 6k....

nick.

 

[Martyn]

4th is better as it produces more load and doesnt rev out as quickly, if you can't do 4th gear runs then 3rd should still be ok.

I still think that MAF is your problem.