89 CRX HF with 1st generation B16A with USDM P30 running OBDI.

Before the 1st attempt, I replaced spark plug, new 4-wire O2 sensor, New TD44U distributor at 16 degree timing and also ran full tank of G2P Smog. I always warm up the cat before the test (drive about 15 min High way and 20 min City).


The result was…..
1st attempt
%CO2 %O2 HC (PPM)
15mph 14.2 1.6 MAX 95 Mean 150
25mph 14.5 0.9 MAX60 Mean 119


After the 1st attempt, I replaced the thermostat, catalytic converter, and used Heet but didn’t really made any difference.

2nd attempt
%CO2 %O2 HC (PPM)
15mph 13.9 1.8 MAX 95 Mean 155
25mph 14.2 1.2 MAX60 Mean 114


Anyone had a similar problem failing only the HC? I had no problem passing the CO (%) and the NO (PPM) but seem to have some kind of problem with HC (PPM). Any help will be thankful.

Forgot to mention but the test was taken at the CA Ref Station.

 

A high hydrocarbon reading is usually unburnt fuel. If the CO reading and the NOx readings are below the limit then look towards an ignition problem. but you swapped that all out...so its either you got a sticky injector, your timing is off or could be gas vapours from a leaky gas tank....on 4 gen f bodies the charcoal canister is back near the tailpipes in the rear quarterpanel and the purge solenoids fail and emit gas vapours in the air so when one goes to do emmisions testing the hydro carbons are through the roof...not saying your charcoal canister has failed but perhaps you have a leak near the rear emitting vapours that gets picked up by the sensors while doing your test.

 

Did you happen to try the test without any additives in the tank?
Additives often mess with the readings and make it hard to tell what you should be looking towards fixing.

It would be awesome if you could get a test done with factory timing, no additives, and the lowest octane gas you can run without pinging. That gives a really nice base to see what direction to go.

How long did you have the new cat on before you tested again? NEW ones need to be run a while to burn off manufactuing residues before they light up and function really well.

Running high octane gas with the timing retarded will drop the NoX level on cars without an EGR. However, your Co will go up so don't over-do it.

 

Thanks for some of the info guys. Will see what happens next....

I barrow the cat from a friend who previously pass emission with a flying color and he only had it on for about 2 month.