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

_________________
JP
GT4DC Treasurer

Grey St185 RC
Silver BMW E46 M3
Multicolour yawn Honda VFR400
Silver Honda Civic Type-R

Temp sensor first port of call IMO

MAF cars will idle high, lean and lumpy if they suck air post maf - it's sucking unmetered air
If idle is solid, afr solid them IMO the ECU is driving it which likely points to a temp sensor issue

P.S.
Dont forget to remind him? he's a hairdressing woofta even if he does have good taste

I'm sure you've covered this already

Another option...

Air lock in coolant system?

Apparantly the dash temp gauge shows "normal" which they all seem to do anyway even when on cold start map.

Rad fans cut in, but IIRC that is a seperate temp "switch" on the rad and not a reflection of coolant temp sensor for dash & ECU.

_________________
JP
GT4DC Treasurer

Grey St185 RC
Silver BMW E46 M3
Multicolour yawn Honda VFR400
Silver Honda Civic Type-R

Erghh a GT28RS kit or a 3sgte conversion will be his only course of action to avoid "hairdressing woofta" remarks. I believe it is erghh a car for the other half

_________________
JP
GT4DC Treasurer

Grey St185 RC
Silver BMW E46 M3
Multicolour yawn Honda VFR400
Silver Honda Civic Type-R

Remember that with regards to the stock dash temp gauge - the ST205 gauge reads normal from water temps of about 65-110 degrees.

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GT4DC Events Co-ordinator
1996 ST205 UK