Right where to start... The Type S failed the MOT this year on high CO emissions and a leaking rear caliper, last year it was borderline on emissions but it got through, i had planned to look into this but never got round to it. Now this year its failed and not throwing any codes so i need some help as im really struggling to solve it!
I dont have the emissions readings to hand, i left them in the car with the garage that i asked to try to get to the bottom of the issue. Im picking the car up tomorrow afternoon as I've lost confidence in them so I can post up the readings then. The upshot is the lambda and HC readings are all a pass on normal idle and fast idle tests, but the CO is way up there on fast idle (fine on normal idle), i think it read about .85 whereas last year it was about .35
The garage mentioned they could smell a bit of unburnt fuel which id agree with and after researching this and the above results it seems to point to a rich mixture ie too much fuel, is that correct?
The car was due a yearly service so i thought ill start there:
- Spark plugs (platinum NGK's) are only 1.5 years old, originally i installed them 'pre gapped' but when i actually measured them they were all out of spec so i set them all to 1.1. They were also a bit sooty which would make sense of the fuel smell...
- Air filter is a K&N item which i cleaned and re-oiled but no matter how much you clean it it never really looks clean...
- Rear brake caliper leak turned out to be the seal below big nut on the handbrake mech which wasn't tightened down enough after i rebuilt all 4 calipers, tightened it up and cleaned it and its fine now.
- Oil was due a change and looking pretty black so i did a flush and added a new filter and oil
So now back to the MOT station for a retest and it failed again, a miniscule improvement (probably due to adjusting the plugs) but essentially same result. One thing we noticed is the car was hunting a bit at fast idle and the CO reading was fluctuating along with it (only by 200rpm), not entirely sure what to make of that except that it seems like the car knows it running rich and its trying to adjust the mixture to no avail, yet still not throwing a code...
Next thing im thinking is maybe that filter is a bit clogged despite cleaning so i order a new 'OEM' style cotton filter and just to be sure f**k it why not throw another lambda on as its cheap anyway and see what happens... So i install the filter and give the ECU a reset, let it get up to temp and see how it behaves, at fast idle it was hunting like before so i wasn't convinced it was solved. While it was hot i attempted to change the lambda but couldn't get it off, i even used a proper socket but all that did was open up as i tried to turn it
Not convinced i decided to look further into it and investigate some of the sensors:
- ECT, when i looked at this it was covered in oil from before i fixed a bunch of leaks so i unplugged it and sprayed it with some brake cleaner, looking closer i noticed what looked like a crack between the plug and sensor end, sure enough it was broken so i ordered a new one. Installed it and tried again but it still seemed to behave the same at fast idle.
- MAP sensor, when compared with the manual the voltage output seems correct, with no vacuum its ~2.9v and with the engine running its ~0.8.
- IAT sensor, i started by back probing this and got a resistance of 6k ohms which is way out when compared to ambient temps, i then unplugged it and checked again this time it was ~3k ohms which still seemed a bit high. So i went to the local breakers and found a 5th gen UK 2.2 and whipped the IAT out of that, when i tested it it read ~2.6k ohms that seemed better so i took it home. When compared to the old one they actually both read almost the same so i think it was actually fine and put the old one back in.
- Coolant was fine, no leaks and only a year old but i re-bled it anyway.
- PCV seems to work fine but took it off and gave it a clean anyway.
At this point i gave up and took it to a more local garage and asked them to check the emissions, if the CO was still out they would change the lambda... They checked, it was out, so they changed the lambda, tested it again and it was now marginally worse
The car has a JDM size cat on it as it should (its only 8 months old) and the garage are suggesting changing it for a bigger one which will of course mean hacking up the exhaust. I explained my next port of call would be the fuel pressure regulator, to which i was told no the issue is too much carbon monoxide so its too much air not fuel... As you can imagine this is the point i lost any confidence i might have had in them.The only other thing i can add is between the last years MOT and this one i had a new exhaust built by Infinity and while there we replaced the CAT with a new ebay item, unfortunately the secondary sensor (CAT overheat sensor) had no chance of getting out of the old CAT without being broken so we cut it off, welded the hole in the new CAT and i just grounded the sensor wire when i got home. I cant see why this is an issue since the sensor doesnt affect the AFR as far as im aware.
Its obviously an issue the cars sensors cannot compensate for so im thinking the FPR is next to look at, other things i thought to look at are exhaust manifold leak (already checked and couldnt see one) and maybe leaking injectors although when i cleaned them a year ago on a home made rig they didnt appear to leak.
So hoping all you lovely lude veterans can lead me in the right direction, please help this is driving me crazy!
Cheers
Max
