Lambda sensor emissions

andy007 · Post by **andy007** » 12 Jun 2009, 09:20

Hi
My M Reg 2ltri passed everything for MOT except emissions. Just over a year ago had complete new exhaust (with Cat) and passed fully. Car has only done 64k from new and is a fab car.
Problem is the Emission results which are as follows:
1st Id Test CO Actual 0.816 Fail
HC Actual 88 Pass
Lambda 0.973 Pass
2nd Fast Id CO Actual 1.496 Fail
HC Actual 123 Pass
Lambda Min Limit 0.970 Max Limit 1.030 Actual 0.951 Fail
Natural Idle CO Max 0.500 Actual 0.758 Fail

Dilema time. Garage wants to do a process of elimination as far as parts are concerned. They plugged in the diagnostic tool which just came up with ' clear all faults 'to start with. This they did and the engine management light went off ( it had been on for a while ) so they thought it would be ok for MOT. By the way it did seem to be using a bit more fuel over the past few months but as I only do about 20 miles a day in and out of traffic so never paid it much mind.

Does anyone have experience of these kind of readings and as what may be the cause? I want to put the car right but as everyone knows, garages have a habbit of playing on our ignorance. I do have a multimeter (sparky by trade) so if anyone can point me in the direction of some basic component tests I would be very grateful.

Thanks in advance
Andy

_kid_ · Post by **_kid_** » 12 Jun 2009, 17:32

im sure someone will be along to help soon but in the meantime have you tried posted on www.honestjohn.co.uk (go to backroom- then the technical section), they seem to have a few guys on ther who know about mot emissions.

MikeT · Post by **MikeT** » 12 Jun 2009, 19:19

If fitted, ECT, TPS, IAT, MAP/MAF give progressive resistances A few K to tens of K I think. O2sensor gives fluctuating millivolt in the 0.1-0.9 range only when up to temperature. etc. What you need is a wiring diagram and possibly the specs of each component you want to test.

Post by **RichardW** » 12 Jun 2009, 20:10

Those lambda values suggest running rich, which tallies with the higher fuel consumption. It might clear if you take it for a good hard thrash, but otherwise I'd be tempted to look at the coolant temperature sensor, or the lambda sensor. HAving said that my Dad's Xantia failed it's first MOT as the lambda was out - taking the ECU out and cleaning the contacts fixed that....

MikeT · Post by **MikeT** » 12 Jun 2009, 22:53

X2

...but I should have also asked if you'd done a service on it? Particularly air filter and oil.