I've got a 1990 greddy miata and just failed because of HC, would leaning the crap out of the car help? It's a 2 speed idle test, and I passed the 2500 rpm test but failed the idle test.

Here are my results:
Idle
RPM: 856
CO2% 13.30
O2% 1.60
HC max:120 measured:173 FAIL
CO% max:1.00 measured:0.01 PASS

2500 RPM
RPM: 2545
CO2% 13.60
O2% 0.90
HC max:140 measured:57 PASS
CO% max:1.00 measured:0.29 PASS

I think I'm going to do new plugs, but am not sure what else I should do along with that. Maybe disconnect the fuel pressure regulator?
Thanks for the help.

 

Oh, and I have an AEM wideband and it was reading about 15 while during the 2500rpm test, didn't notice it during the idle test though

 

HC= hydrocarbons, too high = unburt fuel =too rich.....

what is your setup related to fuel?

 

If its the car he bought from me, just the Greddy-supplied Vortech regulator.

Would a timing adjustment help?

If it helps at all, when I smogged 2 years ago, it had a used FM cat on it, so it might be going bad.

 

you dont want to mess with the regulator, that wont do a damn thing because it only kicks in when you get into boost. What you probably need to do is raise the timing up to like 10* because i bet it is set to like 6* right now and I could see that causing a slightly incomplete combustion at idle. Other end of the spectrum would be too high of timing causing high NO2. Dont forget to set the timing back to like 6* and dont get into boost while your timing is raised up.

 

It is the car I bought from Exhondaman... it's a basic Greddy kit on it plus a J&S Safeguard.

So plugs and timing?

If it was a bad cat, I think the CO% would be higher also, so cat should be good for now.

 

Run a compression test.

 

Exhondaman said he did a compression test just before selling it to me and got 170 on all cylinders.

 

Check timing, I set it crazy-conservative after turbo install to be on safe side.

 

timing should fix your issues set it back to 10, then after the testing retard it back for safety

 

running a lower grade fuel can also help. Regular will ignite easier and burn faster so there will be less unburned HC's left over. Obviously stay the hell away from boost with the crap fuel in there.