car is a 2006 uk subaru impreza wrx hawkeye with full 3 inch milltek exhaust and milltek sports cat.

it just failed mot today due to emissions and lamda levels, I've had the car 5 months and this is 1st mot for me.

garage noticed 1 of 2 lamda probe not fitted to sports cat so could this be the lamda fail 'outside specified limits' - (7.3.D.4) on mot sheet. this lamda doesnt look like it will fit into sports cats current hole that has been bunged up. the other lamda is fitted further down the exhaust on the next exhaust pipe down from the sports cat.

and the high emissions - 5.2.5A, 7.3.D4 - could this due to not getting the cat hot enough on a good blast?

anyone know of a friendly mot testers in the hull, east yorkshire area - can u pm me please?

car has been remapped to 340bhp, 390 torque so if i get lamda probe refitted will car need a remap?

cheers, rob.

 

I've heard of a few people with all different sorts of cars using sports cats, and they always had to get the exhaust piping hot before managing to scrape through the emissions test.

 

Just spoke to the guys I recommended to you Rob, and he says the same, give it a good blast first, make sure its nice and hot and give him a call

 

Took mine in 10 days ago for the mot with the scooby world 100cel sports cat and the guy's in the MOT station had to rev the car for five minutes to get it hot enough to work properly which is normal. Once hot it passed fine. Hope you get it through fella.

 

Can you give us the actual values that were recorded for lambda and the various exhaust gases. If your car is not running at lambda (i.e too rich or lean) it can cause some of the gases to read higher.

Mines on a Milltek with Sports Cat and I've never had issues with the MOT (values are way under the limits and that's without having to cane the car before the test).

 

Your cat will only work correctly at lambda = 1 . Any richer than lambda=1 and the cat efficiency drops right off. Getting a cat really hot before testing burns of any sulphur and other contminants and gives the cat its best chance of working efficently when AFR returns to lambda=1.

The cat doesnt have any affect on lambda but lambda does have an effect on the cat.

As STI Freak says, give us your MOT emissions results so we can help more.

You should have a lambda sensor in the up-pipe to the turbo and after the downpipe sports cat.

I don't believe that you only have one sensor fitted, sounds like there is a boss in the sportscat downpipe that could take a aftermarket lambda sensor if you wanted to fit one. My H&S sportscat has the same.

 

Pretty sure my Bugeye only has one Lambda as std (just after the collector in the headers) I do also have a wideband in the downpipe now as well though. So the bung should be in your downpipe (I have the same exhaust) unless you have fitted an extra sensor.

Mine also passes without issue and without having to get too hot (Miltek with sports cat in centre section 3' Powerstation/Litchfield system) - your issue is your lambda is off which is a mapping/sensor issue.

 

thx for all the advice, just finished night shift, below is results sheet from mot.

 

was it properly warmed up i.e. Oil up to temp not just visually on the temp gauge (water) ? If not then this is your issue as mentioned above.

 

The mixture is too rich, so the cat isn't at fault here.
It sounds as though the primary lambda sensor either isn't fitted, or it's fitted in the wrong place.

 

I agree wuth Alan, doesnt look like anything wrong with your cat, HC values not too bad so it is working, just not enough to pass the test. Get your AFR to lambda=1 and it will be ok.

I would expect a missing lambda sensor to cause a larger problem and check engine light ( MIL ) to come on, although whoever mapped it may have turned of lambda diagnostics.

As always, difficult to diagnose without seeing the car.

 

thx for all the help so far. I just had a look today, I have 1 lamda fitted in engine bay (air filter side) that has a blue wiring sleeve.

the lamda thats not fitted has a yellow wiring sleeve if thats means anything? also it was mapped by andy forrest.

heres a pic of my lamdas


so if my lamda is reading low, could that be a faulty lamda sensor? or has the car maybe been mapped to run richer in fuel? or does it really need both lamdas fitted? there is a hole/boss in the downpipe right near where the yellow sleeved lamda is not connected - i wonder why its not connected.

 

Odd that the second lambda isnt fitted correctly. I assume that there is a bung in the hole and not an open hole ??

I suggest refitting it, check/clear faults in the ECU and go for a drive. If it still fails MOT then it would look like the front sensor isnt working correctly.

Very unlikely it has been mapped to run rich at the speeds/loads that a MOT test uses, it should be in closed loop mode and sit nicely at lambda=1

 

the 2nd lamda is just neatly tie wrapped up about 6 inches from bung near exhaust.

theres a mega tight bung fitted, I will get a garage to refit it and test/reset ecu etc then retest at mot garage.

yeah my Scangauge II obd reader currently says its in a closed loop.

 

Sounds a good plan.

Rear sensor doesnt do a huge amount, mainly used for diagnostics of the downpipe catalyst, so you should have a check engine light come on, however as its been mapped its most likely been turned off.

Fingers crossed it works

 

OK, the diagram looks right. Try it again, but you may have to investigate why the AFR itself looks rich. You may possibly have a duff primary lambda sensor.

 

ah right ok , thx all for the help.

 

update - took it for another mot at a different garage and its failed on emissions and lambda levels again (roughly same readings as before). both garages offered no help and didnt want to get involved with the car once i told them about mods/remap.

so took it to another garage (jap specialist) but they were no interested in helping either.

does does anyone know the colour of the signal wire on the 1st lambda to test it to see if its working? ie on early imprezas its white, so is it white on hawkeyes? as when i took a multimeter reading off the white lambda wire is was 2.5v constant (on 20v setting on multimeter). my car (2006 uk wrx hawkeye) has 4 wires - 2 black, 1 white, 1 blue.

so to recount

1- front pre cat lambda plugged in/wired in.
2- after cat/rear lambda not plugged into exhaust but wired in - i imagine to take a clean reading of emissions.

I'm going to ring a few more garages local on monday about just testing the 1st lambda/fitting a new one.

 

I would use a OBD tool with live readings to check the front lambda signal response, its a lot easier than messing around with a multimeter.

I see no reason for not refitting the second lambda sensor, you may find that its the cause of all your issues.

 

ah right i see, cheers. could you recommend a obd tool with live readings?

 

I have a Autel item from HERE

I have also used a ELM327 bluetooth OBDII adaptor from ebay ( about £18 ) paired with an app called Torque on android, this can display live data such as lambda sensor volts but I have not fully tested it on my Subaru.

 

ok thx alot, i'll buy one of those autels.

just bought one from autel direct on ebay for £60 delivered.