Car has just passed its MOT, but only just got through the emission test. The tester had to re try it several times and get the cats very hot. I'm also only getting about 16mpg around town driving very sensibly (i'm surre it was better than this when i forst got the car 6 months ago). I'm still getting 24-26mpg on the motorway. Could this be MAF, o2 or/and lamda sensor failure?? The car has done 89k miles, so it shouldn't be the cats.
Car has just passed its MOT, but only just got through the emission test. The tester had to re try it several times and get the cats very hot. I'm also only getting about 16mpg around town driving very sensibly (i'm surre it was better than this when i forst got the car 6 months ago). I'm still getting 24-26mpg on the motorway. Could this be MAF, o2 or/and lamda sensor failure?? The car has done 89k miles, so it shouldn't be the cats.
Could be O2, could be spark plugs. Car seems to run well, but run a dynamic MAF test too.
Regards,
Jerry
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If the MAF's were dirty, this would cause the mixture to be lean, which if anything would make it easier to pass the MOT test. I presume you're not getting an engine warning symbol on the dash, and that the car is running OK performance wise? Starts OK and revs cleanly to the redline in the gears? No stuttering or flat spots?
What part of the emissions nearly failed? Several things are measured, and it would be good to know which bit is marginal. If you can post the whole set of results you got on the printout, that might help pin down the problem.
I don't want to be the bringer of doom, but it just could possibly be the catalysts are on their way out. At 89k miles, it would not be completely unheard of, though I have to agree it would be unlucky Sadly, there are many things which can poison a catalyst, including something as simple as a 'bad' tank of fuel.
Basic fault finding for advanced emission test failures:
If a vehicle fails for high CO at idle and /or fast idle then.... if Lambda is too low, the mixture is too rich. This can be caused either by a misfire or by a faulty Lambda sensor. If it's running very rich, the 02 and HC will be higher than normal.
if it has a high Lambda and high 02 (0.5 to 1.5%), the "CAT" could be faulty. Before condemning it make sure its hot enough to work, the Lambda and other sensors are working OK and the exhaust downpipe hasn't got any leaks.
if the vehicle fails for high HC then ...if the CO passes, the vehicle is probably misfiring. Or if the CO fails and the Lambda reading is too low, the mixture is probably too rich and it may also be misfiring.
if the CO fails, the Lambda reading is high and the O2 reading is high (0.5 to 1.5%) the "CAT" could be faulty. Again check out the simple measures above before condemning it.
if the Lambda fails then...if its too high the Lambda sensor may be faulty, the mixture may be too weak or there may be a hole in the exhaust downpipe. If Lambda is too low the sensor may be faulty, the mixture may be rich or the vehicle may be misfiring.
Where vehicles fail the advanced emission tests, remedial action should concentrate on fundamentals such as plugs, timing, air cleaners, mixture settings and the oxygen sensor before changing expensive catalytic converters. Leaks in the exhaust system are a common source of problems.
I'm waiting for an opinion from Thorney motorsport. Results below:-
Any chance the machine is out of calibration? I know nothing about these machines (fortunately) but before i started dumping money in a car that runs good, I would want to be sure I really had a problem. Maybe do normal plugs, O2's maintanence and wait for the next test results.....You passed that's what counts! The person that finishes last in medical school is still called Dr.
Any chance the machine is out of calibration? I know nothing about these machines (fortunately) but before i started dumping money in a car that runs good, I would want to be sure I really had a problem. Maybe do normal plugs, O2's maintanence and wait for the next test results.....You passed that's what counts! The person that finishes last in medical school is still called Dr.
ernest
Yeah, not too worried, she passed so thats the main thing. But will be getting her properly checked out asap.
Sadly, there are many things which can poison a catalyst, including something as simple as a 'bad' tank of fuel.
See The Pic's------->
Linear Mode
