[Mk2] [NA] Mot Failed HC emission help

[GMLMR2]

My 2 failed its mot today on HC emissions , my reading is
MR2, Rev 2 1993 3s-GE no engines mod all stock

HC: 255ppm (limit 200ppm)

last years readings were 112ppm for HC with new lambda, and my old lambda always came out at about HC 54ppm but CO was very high is the new sensor a duff because the HC seems to have jumped now yet lower CO

I changed the lambda sensor last year 2009 and bought one from wwwjustlambda.co.uk because emissions were high in 2008 mot so thought I best replace that before the next mot 2009 which it pasted with lower emissions, but this year there incredibly high for a new sensor and failed on HC weighing in at 255ppm, yet it passed on CO2??? Is my lambda kacked again or is the cat on it’s way out, before the test I did a full service, checked the plugs which are clean and burning right I might add, engine doesn’t smoke and runs well so I’m at a bit of loose end here, any help would be appreciated

[Si_Crewe]

I'm no expert but I thought the cat is supposed to deal with carbon monoxide?
If your CO reading is low then the cat isn't the problem.

High HC sounds more like it's running rich or not combusting properly.

That's all just theoretical though. I have no idea how that applies specifically to an MR2.

[Chris]

HC's is unburnt fuel, a set of plugs could sort it.

[Ian Geary]

in my old VW golf, the following got me through a re-test on HC

- new plugs
- new air filter
- spraying 10k boost (or similar) fuel cleaner intoo the engine with air cleaner off


it worked for me, and was fairly cheap.

Ian

[John145]

You get CO when there combustion is lacking in oxygen. So when you're running rich. You get HC from incomplete combustion, this can be from running rich or lean, or not getting a good burn. ie. ignition system.

How old are the spark plugs?
How are the HT leads look?
Dizzy cap/rotor arm?

I wouldn't worry about the air filter because CO is low

[GMLMR2]

in my old VW golf, the following got me through a re-test on HC

- new plugs
- new air filter
- spraying 10k boost (or similar) fuel cleaner intoo the engine with air cleaner off


it worked for me, and was fairly cheap.

Ian

Thanks for the replies guys

Well I put in a new set of plugs last year NGK ones, I don’t know if the leads have been replaced though, I’ve certainly never replaced them since I’ve owned the car and I’ve had it for 3 years, they’ve got 1993 written on the side of them so I’m guessing there the original ones id say sees as the car is 1993,

I’ve noticed in recent months that there is a strong smell of petrol when ever I have the window open driving I just put it down to a dickey charcoal canister but after reading the post about plugs I went in to Toyota and got a new set and popped them in, I’ve noticed the engine seems to be quieter, livelier, I gapped them to 0.8mm and the smell of fuel seems to have disappeared when I’m driving so I’m guessing it’s helped, I replaced the dizzy cap last year too, and air filter was replaced by a Toyota one last week when I gave it a service.

The car does misfire a bit when first started for about a minute then it evens out but I thought that was normal, at least it says so in the Toyota manual so I didn’t think anything of it.