My freshly rebuilt 1979 Rx7 engine failed the Colorado emissions test on hydro carbons and CO. It's not burning all the fuel. How do I adjust the carb to lean it out at idle?

 

how are they testing it? is it a dyno test or just a stationary idle test.

i don't really know the in's and out's of the Thermal Reactor system, all i really know is that it needs to be HOT to work.

you may also need to be richer for it to work better. there is an idle mixture screw on the carb, right under the giant air bleed screw. turn it until it runs the best, and then about 1/4 turn richer is usually about where it wants to be for emissions tests. for normal driving you want it where it runs the best

 

check your cat's if you don't have them you WILL fail them also having the RAT's nest also helps A LOT replaced my cat's (from factory) to bolt ins from RockAuto insta passed. also my state is Idaho (if that helps) and drive the car till its nice and hot don't turn it off and red line it for a second or two before your car goes in for the test

 

The 1979/1980 doesn't have cats. It uses a Thermal Reactor exhaust manifold.

 

What he said... follow j9fd3s advice on carb adjustments,will likely improve(reduce)emissions to pass the sniffer test.

 

well ****, learned something new....

 

I've always heard the Kali guys say to run it until good and hot and leave it idling until the test. Seems to work for them.

 

I've always made sure that my tank was about 1/2 full and with the highest octane available. I also would put in at least 2 liters of Methyl-hydrate. That really seemed to help burn everything off and give a higher oxygen reading to the equipment they were using. Just a thought...

Dom

 

Dom, What is methyl hydrate? So turn the mixture screw clockwise until the engine starts to "Hunt" (I presume that means "stutter" or miss.) then back up a quarter turn. Herb

 

I too was curious so I googled: Methyl hydrate is also known as methanol, methyl alcohol or wood alcohol.

No experience using it in fuel.

 

the emissions devices work from heat, particularly the THERMAL reactor.

example 1. i went to smog my 79, back in like 2007, and i drove it there, left it running and we pre tested it. it easily passed, really clean actually. the smog guy turned it off, and restarted it ~40 seconds later for the actual test, and it almost failed.

example 2. i had a 190E Mercedes that the former president wanted to buy, and one of the quirks of the cash for clunkers program was that the car had to be registered, and in CA that means it needs a smog. so of course it fails. by like 150hc's. i ask the smog guys if they could do anything and they shrugged, and said drive it around the block? so i did.

with my foot to the floor. the thing had enough brakes to do the speed limit, and it was a BIG block (2 miles?).

when i brought it back, pulled it on, and it passed the test with room to spare.

 

Dom,
I now understand that Methyl Hydrate is Methanol. I understand that Methanol burns much hotter than gasoline. What kind of risk is that putting on the engine?
?
Herb

 

If you are not boosted then it just runs a bit hotter and will make the thremal reactor more efficient. No permanent harm from doing it cause I know you are not boosted and NA.