in california trying to pass smog. before smog check peformed oil change, plugs, cap and rotor, pcv valve, wires.
smog test results
15mph

HC max 135
HC meas 188

CO max 0.87
CO meas 0.27

NO max 1058
NO meas 476

25mph

HC max 115
HC meas 115

CO max 1.08
CO meas 0.21

NO max 918
NO meas 470

last time it passed ok. now since then the cat got stolen! i know for a fact my dad installed the cheapest one there like $100 i think. so should i just intall a CA one from like kragen or autozone? is the universal cat thats on there preventing me from passing? oh and the engine was rebuilt maybe like 20,000 miles ago.

 

Throw some alcohol in there

 

Can't buy them from the local auto parts stores anymore. They have to be installed by a licensed installer, have to meet basic OEM quality standards, etc.

EB may be on to something- tossing some alcohol in may help.

Now, it's only your HC's failing at lower RPM's so it's probably not the converter. Considering the CO is relatively constant, dropping at higher RPM's, supports that. Your NOx readings are well below fail, even at low RPM's, and thus also support proper converter operation.

Verify your valves are adjusted properly and to spec, and if you can, try advancing the timing a bit. That will raise the NOx some, but should also lower HC's.

 

it is proly gunked up, do a couple of seafoam treatments through the engine, WHILE IT IS HOT, and see if that doesn't fix up the prob... if not, then time for a new CAT.

 

Be like all the carbed guys, spray an entire can of carb cleaner into the throttle body while it's running..
Then run the #$%# out of it before you get there.