MOT failure High CO

[James3200GTA]

Hi all,

So I went to the MOT today. Car was in good in all respects but 1: The CO value is too high. Should be 0.5% vol CO at idle and it is somewhere in the 1.0 range.
It's in independent MOT station who only does MOTs. Suppose he's not looking for extra work. He also indicates it's not fully stable at idle RPM and lamba values are good and stable. I'm guessing an airleak somewhere.

FYI: It's fueled by V-power, although the car has been sitting for a while waiting for the dash repair.

Anybody any suggestions as to causes and solutions?

Thnx
J.

 

[Spartacus]

Take it for an "Italian tune up" or get the MOT station to use the donor Honda Civic round the back to do the Co2 test.

 

[safrane]

My MOT station always advised to make sure the can has had a good before the probe goes into the exhaust.

We're you able to do that prior to arranging?

 

[philw696]

Have you got the print out for the emissions ?
If it's been hanging about I would definitely give it a mobile decoke and even change the oil and filter.
Check the plugs too.
Good Luck.

 

[highlander]

happens. garage told me to take it for 30 min blast then bring it back in...........passed no problem. appears they like to be thrashed with a wet willow cane before they are happy

 

[jasst]

My GS passed MOT last week, CO was zero, he said I shouldn't be paying any road tax!

 

[allandwf]

Take it for an "Italian tune up" or get the MOT station to use the donor Honda Civic round the back to do the Co2 test.

How I used to get my Cerbera done lol

 

[James3200GTA]

I changed the oil + filter and checked the plugs about 2-3 months ago. Last test drive after that was abt 80 miles of highway and it has been sitting since then.

Coolant was at normal temp when at the MOT, although I suppose the engine was not fully warm as it was only to the other side of town.
I forgot to ask the other readings, but they were within regulation limits according to the mechanic. He was specific on the lamba values being ok.

While taking things apart again, I noticed the PCV was gooed up where I could not blow air through it with limited exhaling pressure. Cleaned it but now it's leaking in opposite flow direction. Of course SO at Eurospares which usually amounts to NLA.

I'll see if I can get my hands on one, or something similar which fits, run some engine cleaner stuff, give the car a good run for it's money and offer it up again.

Thanks so far and any other suggestions are welcome.

 

[joered]

happens. garage told me to take it for 30 min blast then bring it back in...........passed no problem. appears they like to be thrashed with a wet willow cane before they are happy

Oh you cruel beasty. Your poor car, you need reporting to RSPCA Royal Society for the Prevention of Cruelty to Automobiles!

 

[highlander]

Oh you cruel beasty. Your poor car, you need reporting to RSPCA Royal Society for the Prevention of Cruelty to Automobiles!

sometimes you have to give them what they ask for.............

 

[James3200GTA]

Small update on this issue. I've removed the PCV and attempted to order a new one. That was (of course) NLA. So nothing left then to soak it and give it a good clean.

Yeah baby, it works again after a considerable amount of time fiddling. The joys of small victories
In the meantime the fuel system cleaner came in. Never used that before but the reviews on this particular brand were very good FWIW.

Put everything back together, started the car without the cleaner, and it runs like a 1950's two stroke diesel shuddering the whole car at 1500 RPM. Seems to run really lean, which is counterintuitive to the high CO which is associated with a rich F/A ratio.

Upon further investigation the brake vacuum NRV is leaking. So apparently the PCV issue counteracted the NRV issue, resulting in a half decent running car.
Ordered a new aluminium one and a Kaiser valve as well while we're at it. May run to the car shop this week and change the rubber hoses as well, upto the Kaiser valve at least.

While the attempts are now dead in the water waiting for parts, I pulled the plugs again for inspection. Cylinder #1 + 2 are running a bit rich, which is consistent with CO measurements being higher one bank. Hopefully the cleaner can sort this, otherwise might have to pull the injectors and have them ultrasonically cleaned.

Always fun how one thing leads to another. To be continued...

 

[FIFTY]

Check for air leaks on the intake post MAF it's what failed mine.

 

[midlifecrisis]

Could it be a MAF issue? Genuine question.

 

[Zep]

Given the turbocharged nature of the 3200, I don’t think there is a MAF.

 

[CatmanV2]

Given the turbocharged nature of the 3200, I don’t think there is a MAF.

I've got MAF's (I think) curious to understand

C

 

[conaero]

Winding my mind back 2 decades I think there is an air thing inside or the top of each air box.

 

[Zep]

Back in the day turbo engines didn’t benefit from the modern controls we have now.


It looks like fuelling is controlled by a boost actuated fuel pressure regulator (so fuel pressure and so flow changes with boost levels) along with what must be a map, trimmed by the lambdas. I’ve looked and there is neither a boost sensor or a MAF. There is a rather cryptically named “Temperature Valve”.

 

[conaero]

Winding my mind back 2 decades I think there is an air thing inside or the top of each air box.

Ah, not in the air box but run along the wing and go behind the air box. Wash valves seem to be coming back to me through my brain fog

 

[Lozzer]

2 Map sensors on a 3200, One by the main fusebox on the bulkhead that feeds off the intake manifold, and one bolted under the fusebox on the offside inner wing, that feeds off the driver's side boost hose from intercooler to throttle body.

 

[midlifecrisis]

Given the turbocharged nature of the 3200, I don’t think there is a MAF.

Misread that.