A140 High CO Low HC HELP!!

[tcook]

Hi can anyone help me please.

I have a 1999 A140, i had trouble with MAF in Jan this year, i sent the MAF/ECU to be repaired by BBA-Reman ( very quick and very helpful). Had MAF/ECU re-fitted and car ran fine (better than it had in a long time) Took car for mot and it faild on emissions.

Fast Idle Test
CO - 13.67% Fail
HC - 1343 ppm Fail
Lamda 0.61 Fail

Second Fast Idle Test

CO - 13.27% Fail
HC - 1148 ppm Fail
Lamda 0.63 Fail

Natural Idle Test

CO - 12.79% Fail

Took car to a Mercedes Specialists and they did a star diagnostic and found the front oxygen sensor faulty and a pos ECU/Air mass fault.
Took car to another garage and they found a small ( i mean very small ) hole in the front part of my exhaust, had that sealed.
Had a new front oxygen sensor fitted and took for another mot, failed again on emissions

Fast Idle Test
CO - 0.011% Pass
HC - 8 ppm Pass
Lamda 1.097 Fail

Second Fast Idle Test
CO - 0.011% Pass
HC - 6ppm Pass
Lamda 1.116 Fail

Natural Idle Test
CO - 10.546% Fail

Any ideas on what the cause could be? and or any ideas on how to fix this would be very helpful, everyone i go to from here on seems to be stumped many thanks

Tcook

 

[Silver_Star]

High CO usually relates to the lambda sensor or the cat.

An italian tune up may sort it then take it for the gas test again with it all hot.

 

[npuk]

Words of Warning 17/06/09 and in conclusion

If you have had your MAFS repaired by BBA Reman in recent years you need to check to see if the small 1/16" hole drilled in the top, back edge of the casing which is drilled as part of their repair procedure is sealed.

Left unsealed and you are likely to expose the ECU to possible water/moisture damage which will write off the ECU.

If you had to adjust that screw (Pot)to get your car to run then get your fuel/air mixture checked.

If you are still intending to use the services of BBA Reman for your repair:- Please be aware if following repair and refitting of the ECU/MAFS your engine does not run correctly, then you will need the expert help of a garage with the correct equipment to set the fuel/air flow mixture correctly, adjusting the (POT) screw installed by BBA Reman which forms part of their repair procedure. Without checking the fuel/air flow being delivered to your engine on suitable diagnostics equipment your car may run rich, thus failing the MOT on emissions and the car burning more fuel than it should, or indeed the car running weak, thus you will have less power than you should and you stand a good chance of burning out your inlet valves in the longer term.

For this adjustment to be done professionally as BBA Management have indicated to me it will of course cost you extra money on top of what you have already paid for your MAFS repair.
Further more the document sent out with the repaired ECU's by BBA of which I have a copy does not spell out clearly what adjusting the screw does, or that the adjustment should be undertaken by a professional

From http://www.aclassinfo.co.uk/mypage.38.htm

 

[tcook]

Thanks for the quick reply, i had it set by Mercedes specialsit and have spoken to bba, they have told me that if my pot has been turned to its minimum (which it has) then they may need to pick it up and adjust further!!!!??? but then all emissions would be out not just CO????

 

[Alex Crow]

IMPORTANT, and often neglected in these cases, also not mentioned on albert rowe's pages...

when the a-class MSM ecu has been repaired with a new air mass sensor, the 'boot strapping' operation must be performed before any other work in cases of emission problems. very often this is the only fault - a reprogram with STAR.

the emission test results above suggest this may be the problem in this case, do we know if the boot strapping has been done yet?

 

[tcook]

had another emissions test today and hc co and lamda are up, guy said it s my cat, does any one no where i can get a cat for cheap????

 

[Alex Crow]

had another emissions test today and hc co and lamda are up, guy said it s my cat, does any one no where i can get a cat for cheap????

we are trying to help, but if you want to waste money on a cat go ahead...

 

[star]

IMPORTANT, and often neglected in these cases, also not mentioned on albert rowe's pages...

when the a-class MSM ecu has been repaired with a new air mass sensor, the 'boot strapping' operation must be performed before any other work in cases of emission problems. very often this is the only fault - a reprogram with STAR.

the emission test results above suggest this may be the problem in this case, do we know if the boot strapping has been done yet?

Spot on.

 

[npuk]

had another emissions test today and hc co and lamda are up, guy said it s my cat, does any one no where i can get a cat for cheap????

If you read the whole part on Albert Rowes page about BBA-REMAN and their repair prcoess it does warn if the pot screw is not adjusted correctly and the car runs rich you have good chance of runining the cat.

But have you read what alexander patient has posted? That would be the first thing to check before replacing parts.