Predictable emissions MOT failure! - Alfa Romeo Forum
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(Post Link) post #1 of 2 Old 20-06-15 Thread Starter
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Predictable emissions MOT failure!

Mr GTV (tasty 2000 3.0 V6 variety) just failed it's first MOT in my hands - completely unsurprised! It actually didn't fail on as many things as expected.

- Play in track-rod end
- Degraded CV boot
- Emissions failure!

The MAF managed to actually die in the middle of the emissions test - car died and refused to even start properly until I disconnected it completely. After that it ran super rich and wasn't going to pass in a million years! Weirdly it only failed the fast idle tests - and it passed on HC (easily) and lambda (by the skin of it's teeth). CO result was 1% (limit is 0.3%) though, thus the fail.

I'm a little confused - the lack of a MAF should cause it to run super rich - should that fail on hydrocarbons not CO? I'm trying to work out if the problem is MAF, thermostat (which is doing the dropping to 70 thing that apparently means its broken) or maybe the CAT?

Car recently had a cambelt change at Autolusso, it's been running rich for a long time thanks to some suspicious amateur cam timing, so I'm worried that might've killed the CAT.

Anyone had similar emissions tests results and successfully diagnosed the problem? Any advise would be hugely appreciated!

Last edited by Tomelliott; 20-06-15 at 16:12.
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Don't think lack of MAF would make it run rich, that would be damaging to engine. ECU probably defaults to a mean setting. Lambda sensors should try to correct for rich mixture but without MAF, ECU can't know the amount of air entering engine. New MAF and see how you go.
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emissions , failure , mot , predictable

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