Hi guys, I'm at a loss and I have no idea what to do, any advice would be massively appriciated.

I own a 1992 registered subaru impreza Wrx import. I have just had it in for mot, and it failed on emmisions, but only on the lambda reading on 1st and 2nd fast idle. It was also only out by about 0.1%.

It failed on a couple of other bits aswell so I took the car home and fixed those bits, banged a bottle of emmisions cleaner, took the car for a spirited drive to get her warm, drove onto the ramp for retest and poof!!, as if by magic every single reading on the screen was massively high. The Co reading had gone from a pass to 4%+ and the others where as bad. Took the car away again bewildered, read the ecu and it was showing an ivac fault. Cleaned and resolved that and ecu fault codes are now cleared. Also replaced the lambda with a denso replacement, took back for another retest after a thrashing to get hot. Was better but still nowhere near a pass, Co was about 3%. Any ideas what could be going on and why it seems to have changed over night? I will say the car is decatted, however this was done before the initial test, and the mot tester informs me that with the car being a 92 it is before the manditary year of 93 for a cat. Also have the usual cone filter etc, but again all done before I first took it in and passed on those readings. Car is now out of mot, my missus is baking a sprog and it's the 7th day for free retest tomorrow so I desperately need it legal. Any suggestions on something I can do to even scrape it through the mot so I can get it resolved before next test in a year's time. P's unfortunately it's not the sort of garage where you can leave 20 quid in the ashtray and the emmisions magically pass lol. Please help guys. Thanks

 

is it being tested as a 92 import? i believe cat was not applicable on even late 90's IMPORTS.

No expert but cone filters are a detractor -get rid IMHO

out of interest what does your log book claim the car to be? it's bound to be wrong, eg GL (ignore, I re read and you wrote 'registered')

 

thanks for the reply, I've asked a couple of times at the mot station and they're adamant there testing it for the right car, although when I look at the emmisions printout it's stated a 1993 uk registered car, originally fitted with calalytic convertor. It's a real head blagged tbh.

 

There was something I read about the very early imprezas that if the mot guys can't find the exact model of car on the database then it gets a very relaxed emissions test. I'll ask my mate, he a mot tester.

 

think that might be the issue then

 

Does this help? From the VOSA book on emissions.

 

Oh, and I couldn't find your car in the annex that's mentioned, so 3% is a pass for you.

 

Thanks for that piehole1983, it's funny you posted that as I was just reading something similar myself. I'm pretty sure they're testing the car on the wrong settings but convincing the garage of it seems to be another issue. I've asked the 3 times and they're adamant it's correct. I think they feel like I'm trying to tell them their job. Maybe showing this will help. Thanks again

 

If they're testing it as a UK Turbo, or Turbo 2000 then according to the annex it 0.5% maximum. Because your exact model is not in the annex then it has to go to the 3.5% CO maximum and also importantly, no lambda test.

 

Show them this:

https://www.gov.uk/government/upload...th_edition.pdf

 

There actually a newer version of that document but reads exactly the same for your car.

 

As above, garage are testing against later model-year, UK-spec regulations, not the less-strict earlier import regs they should be. That said, wayward Lambda readings usually suggest unmetered air getting into the intake somewhere, or exhaust gas leaking out somewhere it shouldn't be. How steady does the car idle or hold a fixed amount of revs when it's warmed up?

 

Really appreciate these reply guys as it's putting my mind at ease that what I was thinking was correct, they are testing it as the wrong car. As far as I can see my car is not on that list as the model code is either non existent on the vin or if you count the dash it's a 0. Do you think I could speak to someone at vosa who may ring them and point out their mistake? Again thanks for the help guys.

 

Thanks for the reply mark, that's the most annoying thing as the car runs beautifully better than any impreza I've owned before. As far as I can see there is no lambda test on the less strict test either.

 

sit-rep?

 

Nobody can help you properly if you don't post the readings exactly as presented;

I don't understand what you mean by lambda is out by 0.1%. Most emission testers reports lambda as a ratio of air to fuel, not a percentage.

The target is 1.00 the limit range is 0.97 to 1.03, where 0.97 is rich and 1.03 is lean - the latter (lean) is very common with exhaust leaks and intake leaks between MAF and turbo. The former (rich) is common due to sensor faults or air leaks between turbo and manifold (including aftermarket dump valves).


Carbon monoxide is measured as a percentage...are you mixing it up with that???