Friend has a MR2 Roadster with the 1.8 140bhp engine. (import car)
It has just failed the MOT on emissions...
1) idles at 1600rpm
2) Lambda = 0.975 (= 14.33:1 AFr so running rich)
3) CO = 0.65
4) HC = 52PPM
Apprently has been to Toyota and they charged him £90 and said they don't know what the problem is!
My thinking....
From the 5-gas analysis chart http://www.autoshop101.com/forms/h56.pdf
it is running rich and the high CO is in keeping with the 14.33:1 AFR
therefore.. Items to check for
1) vacuum hose leak somewhere (hence 1600 rpm idle)
2) check throttle plate & ISC valve for gunk and clean.
3) clean MAF
4) dodgy o2 sensor/sensors?
5) engine water temp screwed hence still on cold start map.
My thinking is that as it is consistent rpm & AFR the lambda is screwed (not going in to closed loop). (or engien temp sensor) I would have expected it to idle high but AFR correct if it was just a vacuum leak. Alternatively with a rich mixture from dodgey O2 this would cause idle speed to be higher than normal (what I think is happening)
I have no idea how to check for codes or O2 sensor operation (is it wideband / narrow band etc) but suspect it will need a MrT diagnostic or OBD2 type code reader.
So any bright ideas/comments on my thoughts/you idiot comments
