MOT Emissions Failure

First MOT since I picked up the beast in August....
Few advisories on bushes but its being fully poly bushed in the next few weeks so no problem...

CO % max allowed was 3.50 and my value was 4.19
HC ppm vol max allowed was 1200 my value was 1298

All means very little so thought I would ask the knowledge base for tips tricks etc... from the Guru's

need more info than that! and live data readings from diagnostics but at an educated guess lambda probe or probes faulty (you have 2) cat converters.

change the plugs and air filter, give it an oil change. probably sort it out, if you have got cats, then give it a bloody long run at highish speeds.

As pointed out before, assuming the standard service items are in order, if it has a cat take it for a hard drive just before the MOT to get the cat nicely warmed up. To bring your hydrocarbons down try adding a bottle of Lucas Engine Oil Stabilizer to the oil - I'm not into snake-oils but this stuff really does work. It cuts oil consumption drastically and reduces hydrocarbon emissions. None of the other "equivalents" (STP etc) I've ever seen actually work - Lucas does - trust me! Assumption#2 Of course your engine oil isn't over-filled is it? Which will cause high HCs on the test.

ashbash2403 said:

First MOT since I picked up the beast in August....
Few advisories on bushes but its being fully poly bushed in the next few weeks so no problem...

CO % max allowed was 3.50 and my value was 4.19
HC ppm vol max allowed was 1200 my value was 1298

All means very little so thought I would ask the knowledge base for tips tricks etc... from the Guru's

Click to expand...

Get the multi meter out and check your air flow meter. Assuming you're running hot wire injection, do a search in the V8 section, plenty of info in there about how to check AFM especially CO trim.

6704nathan said:

need more info than that! and live data readings from diagnostics but at an educated guess lambda probe or probes faulty (you have 2) cat converters.

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Unfortunatley thats quoted direct from the emissions teston the MOT nothing else to add to it...

1992lse said:

change the plugs and air filter, give it an oil change. probably sort it out, if you have got cats, then give it a bloody long run at highish speeds.

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Plugs Filter and Oil all done in last 300 miles... proper NGK expensive jobs from a friend, Filter is the K&N Red one which fits in the std trumpet. Oil done about 1 month ago and about 300 miles if that done on it. Cheers

Its has a new Stainless exhaust system properly fitted. Will look for the Lucas stuff and give it a good blast out before the MOT... problem is you can't pre check easily unless you have the kit to do it which I don't.

6704nathan said:

need more info than that! and live data readings from diagnostics but at an educated guess lambda probe or probes faulty (you have 2) cat converters.

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From my experiences of failing lambdas (not on the Rangie) the mixture normally goes a lot richer than 4 odd percent CO - unless it's just mildly contaminated or something. Checking the output(s) with a decent digital volt meter would soon verify the lambda probe(s) anyway.

also in my experience failed lambda probes usually get up really high into the 8% co range and cats failing would be around the 4% mark BUT another forum member in the last couple of days had an mot fail with similar figures to yours on emissions and had a duff lambda probe but he had live data readings to go on.
your co% is to high for service items really need to get it plugged in else it is all just guessing and could get expensive when you start replacing lambda probes cats air flow meter etc!

All sorted.... He said ! Adjustment on the airflow meter & dizzy timing was way out. Good run and print outs showing it running leaner now. Drives smooth and may get a bit of mpg boost. !

MOT Retest passed with flying colors....
CO Max 3.50 actual 2.42
HC Max 1200 actual 542

Bosh! Another year... now just to get the Polybushes all in and heavyweight Rear arms

Nice one - another year's Ranging!

ashbash2403 said:

Adjustment on the airflow meter & dizzy timing was way out.

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There's a shock! (NOT) It's usually something simple. Do keep a check on both timing and AFM, every few months should keep it right.