mot fail - high co

[big_al]

evening people,
after spending 3 days on and off replacing front shocks , front disks, overhauling the calipers , new arb bushes and droplinks, adjusted front ride height, fixed leak which was flooding the drivers footwell, and a bit of the obligatory welding thrown in for good measure the old girl was looking in pretty good shape for her yearly medical.

she breeezed all the bits i had doubts about and failed on high CO !

well, i have only had a brief chance to look at it . i took all 4 spark plugs out (yes its the 2.4 petrol version) and they are all light grey-brown . obviously this would indicate running slightly lean and healthy.

i am doubtfull whether its the cat. i have no history of this vehicle since i bought it at auction , but when i bought it last year the cat looked fairly new , and the emmisions last year were extremely low (and commented upon by the tester).

short journeys can kill lambda sensors fairly quickly (housewives syndrome) which is all the old girl does , but this normally soots up the sensor and causes the engine to run rich.

if it failed on high CO then surely it should be running rich ? any advice? i just hate someone having my pants down and the garage i took it to seems to be a lttle slow on business at the moment. normally you need to book a week or two in advance. at the moment its next day.and i never thought at the time , but they never produced the analyser readings with the failure ticket.

cheers, Al

 

[Deleted Member S]

Oooo you should have got that to prove it fail on the co test :roll: If the lamba is'nt stuck fast you could try & remove it & give it a clean with some carb cleaner. I would then give it a good drop of red ex & then scream the life out of it down the road or drive it at over 3k rpm for about a mile. At 3k rpm the vales rotate aswell as go up & down this then helps to break the carbon off the valves :smile:

 

[big_al]

thanks sweety i'll definately give that a try . but if the plugs look fine and healthy then wouldn't that indicate that all is well engine/lambda wise ? or have i got it wrong . testing time was 17.15 so personally i think the tester didnt heat it up long enough as he was late for his tea or something

cheers, Al

 

[rustic]

Something else to look at is not enough oxygen getting in to convert the CO (carbon monoxide) to CO2 (carbon dioxide) ie have you checked the air filter.

It is worth giving the old girl a thrashing (not the wife) you probably need to get the cat to a high temperature to burn off the deposites that have naturally built up on the cat, you need to go on a long journey and get the cat roasting hot.


best regards, Rustic

 

[(RIP) PLANK]

how much difference it will make i dont know, but they recon most cars run cleaner with clean oil! when was the last time you changed it?

I would also ask for the print out to prove the co2 emissions! otherwise how do you know waht you are trying to fix! if they have to put the probe up again to do it, this will prove it one way or the other for sure!

 

[Jocky]

You can get this problem if the inlet manifold gasket is leaking. It doesn't need to be much of a leak.

I've had this problem with an Astra & Cavalier. These were single point injection motors.

Don't know what the T2/Mav petrol set is like. Is it single or multi point injection. If you can get near the manifold have a listen with a long screwdriver.

:smile:

Sounds dodgy to me if he didn't give you the print out. I'd take it else where and get it tested :!:

 

[big_al]

it was booked in today for fault finding , re mot'ing etc . i've had little time in the last couple of days to have a better look at it (i've been looking at pathfinder aventura's 8) ). anyway , it seems my fears were unfounded . The 8 mile journey to the garage this morning was spent in 3rd gear almost all the way at about 4k rpm. The garage was very apologetic when i asked for the analyser print off and offered to show me it fail there and then. Being in a hurry i just left it with them. It has now passed . all they did was add some kind of petrol additive (probably redex as stated above) , gave it a good thrashing and it passed ok . He did say it had a bit of a missfire at low rpm but didnt look into it because it passed . Free retest and an hours labour . Sounds good to me :smile:

cheers for the replies chaps . good stuff to know for the future.

 

[Deleted Member S]

Glad to hear it's now pasy :smile: But driving for 8 mile in 3rd has given it a good work out & prob removed a lot of carbon off the valves making them seal better

 

[big_al]

since i'm selling it to the father in law i better give this missfire a looking at .
does anyone know the spark plug gap there should be on these things?

oh and i better change the oil too since i have no history of it ever being changed

 

[Deleted Member S]

does anyone know the spark plug gap there should be on these things?

I would think Hummingbird & Mav will know as they as they have 2.4 petrols. (sorry can't think of anyone else at the min )

 

[Terranosaurus]

Plug gap should be 1.0-1.1mm or 0.039-0.043".

If you buy new plugs and they are not gapped correctly it is because they have been dropped on their ends, these days plugs come ready gapped, I've not had to adjust a st of plugs in a long time. In th days of "CCC" (anyone remember that mag) Dave Walker (master engine builder) recommended returning plugs that weren't gapped correctly - and CC folded over 10 years ago.

Check the condition of the rotor arm and dizzy cap, they tend to get neglected these days as so few vehicles have them now everything is distributorless.

 

[ronypony]

I always take my vehicles to our local M.O.T Testing station rather than a garage....the testing station does not do any repairs to vehicles..they only M.OT. them. This means that I can be absolutley confident that any reasons given for failing my vehicle are genuine.

I then either fix the problem myself or take it somewhere if I can't do the repair myself...back to testing station within 14 days and they don't charge a retest fee.