MOT failure CO level too high - cure by thrashing the car

[RumblingGrunt]

An odd one here. CLS63 failed MOT on Friday as CO level too high. No faulty exhaust or sensors, all visually good. Technician asked if I tended to drive gently, as they thought the converter might be sooted uip. Answer was 'Yes, as I don't want to lose my licence".
"Can we drive it around Milton Keynes at higher revs than usual?" Well, OK if that will make it pass - and so it came to pass!
Any suggestions on how to avoid this daftness next year?

 

[V6Matty]

An odd one here. CLS63 failed MOT on Friday as CO level too high. No faulty exhaust or sensors, all visually good. Technician asked if I tended to drive gently, as they thought the converter might be sooted uip. Answer was 'Yes, as I don't want to lose my licence".
"Can we drive it around Milton Keynes at higher revs than usual?" Well, OK if that will make it pass - and so it came to pass!
Any suggestions on how to avoid this daftness next year?

Drive it like you mean it

 

[brandwooddixon]

The good old Italian tune-up!
Do you tend to do low mileage and speed journeys?
Most cars benefit from a spell at higher revs occasionally and getting up to temperature for longer periods.
You can achieve the same by selecting lower gears to get the revs in the 2-3000 rpm bracket occasionally and a longer motorway journey.

Seriously though, I thought that as part of the test they were meant to run the engine at 3000 rpm before performing that test, just to clear out the exhaust.
Could this just be an excuse?

 

[tpn]

Put some Dipetane in the tank. Great stuff

 

[harrye500]

As V6matty its a 63' so drive it like your life depended on it (from time to time, legally) bla bla, that's my legal get out clause!

 

[alexanderfoti]

I use this philosphy on every engine I own.

So far never had a clogged egr, never had a clogged PCV, never had sooted up plugs. I say it so much, my wife makes fun of me when I say "drive it hard!!!"

 

[Blobcat]

I use this philosphy on every engine I own.

So far never had a clogged egr, never had a clogged PCV, never had sooted up plugs. I say it so much, my wife makes fun of me when I say "drive it hard!!!"

If it’s not banging off the rev limiter and the valves aren’t “floating” then it needs canning a bit more…

Imagine it’s a holiday hire car and you’re late to check-in…

 

[LostKiwi]

Seriously though, I thought that as part of the test they were meant to run the engine at 3000 rpm before performing that test, just to clear out the exhaust.

Exactly what my MOT guy does.
If it fails on first run he holds it at 3k rpm for about 2 minutes then immediately retests.
It actually says in the guidance notes to do that.

 

[BPD07]

Take it up Chichley Hill (just past Newport Pagnell). Wait until you’ve cleared the bridge to see if there are Federales in the lay bay and then floor it. It’s known as an Italian Tune up, you don’t need to go illegal just floor it and get the rev counter round to the naughty side a few times.

 

[rayhennig]

'Yes, as I don't want to lose my licence"

Chop it in for a 200D.

RayH

 

[alexanderfoti]

If it’s not banging off the rev limiter and the valves aren’t “floating” then it needs canning a bit more…

Imagine it’s a holiday hire car and you’re late to check-in…

Much of our customer use that philosophy with our courtesy car. I can always tell who

 

[Blobcat]

Much of our customer use that philosophy with our courtesy car. I can always tell who

Bet it’s never failed an emissions test though…

 

[alexanderfoti]

Bet it’s never failed an emissions test though…

Not only that, its a 2005 with a DPF that I HAVE NEVER TOUCHED!!!

 

[AMGeed]

Take it up Chichley Hill (just past Newport Pagnell). Wait until you’ve cleared the bridge to see if there are Federales in the lay bay and then floor it. It’s known as an Italian Tune up, you don’t need to go illegal just floor it and get the rev counter round to the naughty side a few times.

The problem with that is you are well above the NSL within seconds in a 63, even in lower gears.

 

[alexanderfoti]

90 mph at the top of 2nd on the s class....

 

[noonboots]

An odd one here. CLS63 failed MOT on Friday as CO level too high. No faulty exhaust or sensors, all visually good. Technician asked if I tended to drive gently, as they thought the converter might be sooted uip. Answer was 'Yes, as I don't want to lose my licence".
"Can we drive it around Milton Keynes at higher revs than usual?" Well, OK if that will make it pass - and so it came to pass!
Any suggestions on how to avoid this daftness next year?

Do a few miles on the motorway or the local bypass to get the cat hot before the test is the usual solution. That's all they were doing. As a catalyst gets older its gets less effective.
For the same reason, cars fast idle when cold to get the catalyst to warm up quicker, as soon as a certain temp is reached the idle goes to normal.

 

[JBell]

Drive it like you stole it

Corrected that for you