ive had my99 uk turbo moted this week and it flew thought but the emissions are mental high.
the exhaust is standard apart from a magnex 3" down pipe and it had a new lamba last year but it just wont go though. its only been run on v power too.
the tester says it could be the maf, could this be right as i dont wont to shell out £350+vat if its not needed. he also said that when the maf fails the engine runs lean witch causes pistion 3 to fail resualting in a blown bottom end. is this right plz help

 

This downpipe. Has it got a catalyst in it?

Two things there. First of all new MY99-00 MAF sensor inserts are around £90 to £100 from a Subaru dealer so where you got £350+VAT from I have no idea.

Secondly, how exactly did it fail? CO too high? If so, before you go any further, answer the question above about the presence of the cat in the downpipe above. If you have a decat DP it's hardly surprising it won't pass, even assuming you've kept the OE centre cat. If you have a sports cat then that complicates issues slightly, but we need to know before we can advise you more accurately.

This is largely true - although it's not just the No. 3 piston that can suffer from this, lean running (with consequent knock) can do a number of detrimental things. No. 3 tends to be the weak link as it's at the "far" end of the standard fuel rail and, coincidentally or not, nearest the heatsource that is the uppipe and turbo.

However, it is unlikely that a duff MAF sensor would cause an MOT emissions fail so this doesn't in itself suggest that your sensor has gone. Tell us about your downpipe and all may become clear.

 

Its just a 3" magnext with no cat or sports cat, but the center is standard as is the up pipe and headers.
Is it not possable to scrape through with just the to cats in place?

The garage informed me it would cost £350+vat for a new maf, i have no idea what they cost.

everything is fine apart from co2 its reading anything from 600 up to 15000 and 300 or less is a pass.

 

try cleaning the maf sensor and changing or regapping the plugs first get a new air filtercheap one still cheaper than getting a new maf take the car for a massive blast so that the cats are warm just before mot and it should pass once u change anything on the car reset the ecu by removing the battery terminals should be ok done this on mine as I thought my maf was playing up and my emmisions were the best I have ever sen on a 10 year old car

failing that try putting std downpipe back on and resetting ecu

 

you need the cat on the down thats the one that maters dont get sports there poo if you have a mate with scoob put his or hers on if not ebay if not try offer a drink that worked for me but no cat no pass so dont spend money on anything else hope this helped

 

you wont pass without the cat in the downpipe

 

Which impreza has two cats?

I thought the centre section just has a sound deadening resonater

 

ok ive got hold of a down pipe i will try that and post the resaults

 

QED. Your car is failing because you've removed the main cat (i.e. the one in the downpipe). The only one left is smaller and less efficient, because it runs colder.

Two? Your car only has one cat in it at the moment, the one in the centre section. Sometimes, if you are lucky, you might just be able to get it to scrape through provided the centre cat is in good nick and you get it really hot first. However, it doesn't sound like you've got a monkey's given the CO numbers you posted. You need to put the OE downpipe back on.

Proof positive that this garage knows very little about these cars. If you still have the OE downpipe, put it on. You can always take it off again afterwards.

The ones that don't have one, or three.

On your car that's correct. UK/EU cars of the same era have a second cat in the centre section.

 

cheers splitpin thanks for the help
and everyone else
much appreciated