MOT fail on V high emissions - M104 3.2. Ideas?

[mccrackenj]

Chaps

The E320 (1995 W124 3.2) failed MOT today on emissions. Last MOT (less then 500 miles ago) was 0.16% CO2. This time 8.32%!

What could have changed to make such a massive difference? The test nation is about 8 miles away and I idled for a bit, so should have been warm enough.

Is my cat fooked? Or something even worse?

Thanks

[MRichards99]

I'm not an expert on this but did the car sit around for an hour or two before the test (did you wait for the MOT to be done or leave the car with the MOT testers)? If I have any concerns about emissions, I'd get the car burning hot - good little hoon and on the motorway for a junction or two then wait for the MOT to be done there and then. Cataclean can help, though there's mixed opinions on this product. If the last MOT was < 500 miles ago, that implies you haven't run the car that much over the previous 12 months - maybe the car just needs an extended drive to clear everything out?

[PositronicRay]

This'll be an HFM car so 1st step will be to read the codes.


A faulty temp sensor may be holding things a bit rich. They also had the infamous failing engine wiring loom, a proper electronic diagnosis is in order.

IIRC upper CO2 limit is 0.20 so you're way off.

Edited by PositronicRay on Friday 21st September 17:07

[mccrackenj]

MRichards99 said:

I'm not an expert on this but did the car sit around for an hour or two before the test (did you wait for the MOT to be done or leave the car with the MOT testers)? If I have any concerns about emissions, I'd get the car burning hot - good little hoon and on the motorway for a junction or two then wait for the MOT to be done there and then. Cataclean can help, though there's mixed opinions on this product. If the last MOT was < 500 miles ago, that implies you haven't run the car that much over the previous 12 months - maybe the car just needs an extended drive to clear everything out?

No, it didn't sit. MOTs in NI are done at govt test centres, so you have to remain with the car at all times. I sat outside for 15-20 mins beforehand, but the car was idling for at least 5 mins of that time. Maybe it does just need a good run.

1 other piece of info, it had an rough idle problems a local mechanic fitted a new AFM on Tuesday which cured that. Is there any chance the new AFM could be at fault? That would be typical of my luck with this car!

[ruhall]

Was the AFM /MAF / HFM fitted a genuine part? There's a good chance that the two issues are linked. Not familiar with that particular engine (well, can't recall much about it now) but a check that all hoses/clips etc are connected properly would be a start.

What's the air filter like. Might be worth trying some new fuel, perhaps super, and giving it a good run to clear things out if it's been stood around for quite some time.

As already stated, check for error codes.

[mccrackenj]

PositronicRay said:

This'll be an HFM car so 1st step will be to read the codes.


A faulty temp sensor may be holding things a bit rich. They also had the infamous failing engine wiring loom, a proper electronic diagnosis is in order.

IIRC upper CO2 limit is 0.20 so you're way off.

Edited by PositronicRay on Friday 21st September 17:07

Wing loom all replaced (£££!!!) so I hope it's now't to do with that.

[mccrackenj]

ruhall said:

Was the AFM /MAF / HFM fitted a genuine part? There's a good chance that the two issues are linked. Not familiar with that particular engine (well, can't recall much about it now) but a check that all hoses/clips etc are connected properly would be a start.

What's the air filter like. Might be worth trying some new fuel, perhaps super, and giving it a good run to clear things out if it's been stood around for quite some time.

As already stated, check for error codes.

I'll be sticking a new air filter on it and leaving it in to a local mechanic for investigation. Fortunately I still have the old AFM, so if that's all it is I'm laughing.


Cheers for the responses everyone. I'll let you know how I get on, just for info.