1.6 GTi - MOT Emissions Failure

Hi All,

Had my 1982 1.6 GTi MOT'd earlier today…..unfortunately it failed on a few minor bits and bobs, but the major one is emissions. Carbon Monoxide (CO) was 5.0%, the limit being 4.5%. The HC was 4620PPM, which is massively over the 1250ppm limit.

I've done a few hours searching on the forums, and can I just confirm that i'm barking up the right tree with regards to resolving this…

1) CO is high due to running rich? This would make sense as even when the car has warmed up, the exhaust fumes absolutely stink of unburnt fuel! Should I attempt to trim the mixture down a touch with a 3mm allan key in the fuel metering head? If so, how much by?

2) HC is high due to problem with ignition system. I've checked all wires, vacuum pipes, plugs are new, as are leads, filters etc. Would it be worth investing in a timing strobe and trying to sort this myself?

Any other tips and hints are welcomed, as I only have 10 days to get this sorted and get restested!!

Thanks

Matt

Yep, the mixture needs turning down, but unless you have the gas analyser, its hard to know how much by. Smelling the exhaust, needless to say, is very inaccurate.

High HC is normally due to a misfire. You can normally find out which cylinder its on, by pulling ignition leads off one at a time, and noting how much the idle speed drops, or roughness increases. The suspect cylinder is the one which it doesn't get worse on.

New plugs, new leads and cleaning up the inside and outside of the dizzy cap and rotor, normally solves things. Also, look for cracks (dirt will build up here and the high voltage will track across it, reducing the strength of the spark). Also, check the HT connections are secure.

Many Thanks for your help Paul - Think would make sense as the car is a little "rough" at idle, so i'll give the HT leads and Dizzy a check before I go any where near the mixture screw! Plugs are new and gapped, so I think i'm happy to assume they are OK

Luckily the MOT place are willing to give me a couple of goes on the analyser before the final retest

I'll keep this thread updated….

Could also be the injectors arent delivering a finely atomized spray.

Mine failed on this the other day (Carbon Monoxide (CO) was 7.5%!!).

One thing the tester did point out was that a really dity Air filter does not help matters. For a the sake of a a few quid I changed mind and took it back for them to adjust. All done and passed ! Happy man!!