mrk_h

Hi all,

Just failed the MOT on excessive CO2 emissions (off the scale) , and the retest as well, with a different 02 sensor . Can anyone suggest anything really straightforward to check before it goes to the dealer?

It's MY 99 with PPP, Blitz Induction ,ScoobySport downpipe and Power Engineering Sports Cat centre section . It was spot on last year with the same mods. Idle is fine and the fuel consumption is okay ( well, normal..!).

Thanks in advance.

ozzy

Well it's either not fuelling right or the cat's not doing it's job. Have you tried with an OE cat. I would suggest the MAF sensor is checked too.

My MY99 passed easily with TSL DP, OE Cat and STI backbox.

Stefan

Dark Blue Mark

That Blizt induction kit is a seriousl libility to your MAF. Get shot of it.

As Ozzy says, the MAF will be the culprit. You can get one from the main dealer at about £90.

Just wories me how many MAF failures are picked up only at MOT time, meanwhile its probably been running quite lean, every time you boost it

MB

ozzy

Usually a faulty MAF makes the car run too lean, but would this cause poor emissions? I thought it would need to run really rich to do that. That was the symptom when my O2 sensor failed.

Having said that my Dad's Vectra failed on emissions and we only changed the MAF (£150 from Vauxhall, robbing barstewards)

Stefan

Dark Blue Mark

Mine failed the MOT on a dead MAF. CO2 was sky high. I didn't think the MAF would affect the fast idle, but Mr Banks explained it to me, and apparently it does.

MB

mrk_h

Ouch, thanks all for that. I didn't think a MAF failure would make the CO2 emissions go high at all. I 've been lurking on SN for a long time and can't remmber seeing it come up before .

Can someone clear up what ozzy saysis the engine running lean or rich with these emissions? I would have thought rich, but if it could be lean, I will drive much more gingerly 'til its sorted

I think the induction will go too, I kind of knew it was a liability, but it does sound nice .