BMW E91 318i Failed MOT on high CO
Discussion
Just wondering if someone might be able to point me in the right direction here, wifes car has failed on CO reading for first and second idle test, we had similar issues (car blowing smoke) last year and the crank case breather was replaced at that time. He has apparently checked the breather and think it is ok. Car does occasionally still blow a bit of blue smoke.
Mechanic seems to think it is something serious in the engine and out of his comfort zone from what impression I got from him. Car I believe might have been tested cold, Engine oil Temprature was "bypassed - temp guage checked", car failed Lambda on first test but not 2nd
Car has just over 120k on the clock and was fully serviced by same mechanic around easter time
Output is as below
Fast Idle Test
RPM (2250 min to 2750 max) actual 2661 (pass)
CO (No stated min to 0.200 max) actual 1.008 (FAIL)
HC (No stated min to 200 max) actual 89 (pass)
Lambda (0.970 to 1.030) actual 0.969 (FAIL)
Second Idle Test
RPM (2250 min to 2750 max) actual 2661 (pass)
CO (No stated min to 0.200 max) actual 0.664 (FAIL)
HC (No stated min to 200 max) actual 89 (pass)
Lambda (0.970 to 1.030) actual 0.982 (pass)
Natural Idle Test
RPM (550 min to 900 max) actual 870 (pass)
CO (No stated min to 0.200 max) actual 0.141 (pass)
Mechanic seems to think it is something serious in the engine and out of his comfort zone from what impression I got from him. Car I believe might have been tested cold, Engine oil Temprature was "bypassed - temp guage checked", car failed Lambda on first test but not 2nd
Car has just over 120k on the clock and was fully serviced by same mechanic around easter time
Output is as below
Fast Idle Test
RPM (2250 min to 2750 max) actual 2661 (pass)
CO (No stated min to 0.200 max) actual 1.008 (FAIL)
HC (No stated min to 200 max) actual 89 (pass)
Lambda (0.970 to 1.030) actual 0.969 (FAIL)
Second Idle Test
RPM (2250 min to 2750 max) actual 2661 (pass)
CO (No stated min to 0.200 max) actual 0.664 (FAIL)
HC (No stated min to 200 max) actual 89 (pass)
Lambda (0.970 to 1.030) actual 0.982 (pass)
Natural Idle Test
RPM (550 min to 900 max) actual 870 (pass)
CO (No stated min to 0.200 max) actual 0.141 (pass)
MissChief said:
Italian Tune up.
Get it up to temperature then rag the absolute nuts off it. 5,000RPM+, full foot to the floor type thing. Then take it back, see if it still fails. Sometimes works! Chances are it hasn't seen the other wide of 3k RPM for months.
Thanks, was thinking this.. Might take it for a good run tomorrow to open the taps on it and empty the tank a bit which is very full then drop some Cataclean or Forte treatment into it and book it in for next week at another garageGet it up to temperature then rag the absolute nuts off it. 5,000RPM+, full foot to the floor type thing. Then take it back, see if it still fails. Sometimes works! Chances are it hasn't seen the other wide of 3k RPM for months.
helix402 said:
Thanks, it's an N46 variant so looks like it was tested to the right specs given the VOSA data sheet (v19)
te in the catalytic converter. helix402 said:
Ah well, was worth a try! May be the doom and gloom 2nd option.
Thinking it's the Valve Stem Seals having done some research this morning, trying to decide now on chopping the car in, paying for a repair or getting the tools and parts and doing myself tho that means Mrs buying a run around to give me the time to do itBurning oil will give high HC first, when yours is within tolerance and constant - CO is little affected by things like valve stem seals - I think that idea is a non-starter.
Lambda damn-nigh on but CO high = get the cats properly hot via the Italian tune-up, for an extended drive, then take it back for the retest - its free if within 10days of first presentation, iirc.
ETA: afterthought, also check for slight exhaust leaks between engine and cat/lambda sensor - entrained fresh air here will have the ECU trim back towards lambda = 1 but could be slinging too much fuel through to compensate for, hence high C0. Just a thought.
Lambda damn-nigh on but CO high = get the cats properly hot via the Italian tune-up, for an extended drive, then take it back for the retest - its free if within 10days of first presentation, iirc.
ETA: afterthought, also check for slight exhaust leaks between engine and cat/lambda sensor - entrained fresh air here will have the ECU trim back towards lambda = 1 but could be slinging too much fuel through to compensate for, hence high C0. Just a thought.
Edited by Huff on Monday 1st June 19:28
Gassing Station | BMW General | Top of Page | What's New | My Stuff