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mattiekane

MOT fail on emissions

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Right guys, Impreza failed it's MOT on emissions.
 
CO fail(high)
HC pass
Lambda pass
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Also noticed when your driving and lightly press the throttle there is a missfire sensation.
 
Cleaned throttle body
Checked pipe work
Had lambda sensors
New injectors
New spark plugs
 
No fault codes, no engine management light......no fricking idea haha
 
 
 
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Maybe nedes a tune up/plugs etc? Did you give the car a hard run just before the MOT? Hot cats work better I think.

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Yeah, tanned is behind to the test centre still no luck, even tried it with no air filter in on the off chance

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**Update**

Since doing injectors, CO is down to 0.02(Pass) HC 57(pass) lambda 1.4~(Fail)

It's also hunting at idle and what sounds like a misfire when rev are held steady at 2000rpm-2500rpm



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Assume you've got the standard cat in place ? Have you tried taking it for a long drive before the test to heat the cat (hot cats work better) .

As for the misfire without a code , spark plugs ,coilpacks ,air leaks , tgv's, did you fit the injectors with new seals , icv clean , maf clean .

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Only just seen this, I've put it into a local garage as time restrictions and a poorly child is preventing me from getting this sorted, everything pointing at the mass air flow sensor been duff now, but gonna wait and see what the garage comes up with

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If your running a aftermarket  "oil'd filter" or induction kit, (like a k&n ) it might have contaminated the element. So you might just get away with cleaning the maf element with some brake cleaner .

Hopefully it might solve the issue completely and would be Much cheaper than buying a new maf .Then possibly finding out it makes no difference to your symptoms,  cos it's something else at fault 😉

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Yeah I tried that lol
Unfortunately (possibly fortunately) the car is pretty standard, just DV and cat back blitz nurspec.

£150~ for the maf was the cheapest (definitely)genuine item I found. Found a few denso's for £60ish but couldnt confirm they where genuine

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Haven't got anyone local that you could swap maf's with to see if it resolves the issue before parting with hard earned?

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Unfortunately not, the joys of living in the middle of nowhere haha

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@savagebulldog

What would you take from that lambda sensor reading?740e69d31fbf9cb8d14fcb772774e311.jpg

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Oh, and the garage tried a maf in but didn't make a difference, that have been through it and can't find a reason for it running the way it is, so I'm going back to the lambda sensors I've fitted, questioning the quality and going to refit the old ones on the off chance the injectors actually fixed the fault but dodgy lambda sensors have introduced and second fault

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My wideband reads 14.2 at cruse and hot idle 11.2 on boost ,which is pretty spot on for a boosted boxer lump.

Yours seems to look like its missing or flooding on 1 cylinder , did you fit the cleaned injectors with new seals?

Are all the spark plugs the same colour ?

 

If one is wet with fuel or black with oily residue it might help diagnose if it's a particular cylinder at fault 

 

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Fixed it tonight, swapped lambda sensor back to the old one and hey presto, new one must of been duff

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You an me both, was getting quite stressed with it lol

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Just to confirm, have give it a good run out this morning and drives nice again, no hunting, no hiccups and nice and smooth

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