my vehicle failed the high speed emissions test. the hc and co were high during the high speed portion, and i need to know what i can do (other than put it in the shop) to fix it. is there a certain part or parts that need to be replaced? oh yeah...the smell of the exhaust is rich, someone please help me.

thanks

What model and what size engine is it?

it's a 1994 trooper....don't know what model...i have the vin number...all i know is that it's a regular trooper with a manual tranny and 4 wheel drive...power everything....heated mirrors.....and a 3.2 dohc i think

When did you last tune it up? It could be a number of things it could be a bad sensor Wrong grade of fuel or just the wrong inspector.

i just got it and the inspection is due. i did an oil change..i'm going to change the plugs tomorrow, and i use regular 87 octane gas...is there an additive i can use that will clean the emissions?

I would give it a real good tune up. Plugs (wires if they are over due) fuel filter. And as the additives the only thing I can think of is injector cleaner I would go with a better brand and not a store brand.