dazebreak

This is a stock '95 Civic DX Sedan. I checked and adjusted timing and idle a few months ago, and the belt isn't due. No check engine light.

It passed all visual checks. Here's what I was given for emission test results;

RPM 667 ; %CO2 13.2, %O2 2.6, HC(PPM) max. 100, ave. 17, measured 199 (this is the problem), CO(%) max 1.00, ave. 0.00, meas. 0.08

RPM 2622 ; %CO2 14.8, %O2 0.1, HC(PPM) max. 130, ave. 12, measured 14, CO(%) max 1.00, ave. 0.10, meas 0.02

OH YEAH I AM IN CALIFORNIA

Thanks!

dazebreak

BUMP

I don't know if this makes a difference, but when I brought it in, the gas tank was almost empty.

Also, when I changed spark plugs recently, I found there was oil on the plugs, but not on the contacts. So I think maybe the spark plug head seals or whatever are worn.

I can do a compression test, would that be helpful?

Any other tests or adjustments to try?

It had a new CAT put in last time I got it smogged, but maybe I need another?


Thanks!

24TEN

iTrader: (2)

HC is unburned fuel if I'm not mistaken. I failed for the same last year:

https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/smog-failure-over-hydrocarbons-3079979/

Had my injectors rebuilt (not cleaned) and the results at the 15mph were 13 and at 25mph 6 compared to the original results in that thread. It also dropped the CO% to 0.01 on both 15 and 25mph tests. Apparently sticky/leaky injectors (not fully closing) were the cause of the high HC readings on my 15mph test.

dazebreak

Great thanks for the info.

mx73lol

HC - unburned fuel
CO - inefficiency gas, the lower the better. As close to 0 as possible. Higher numbers mean incomplete combustion.
CO2 - efficiency gas, the higher the better. Somewhere in the 14% range, product of complete combustion.
O2 - should be close to 0, meaning all the oxygen is being used for combustion.
NOX - produced when combustion temps are above 2,500 degrees.

I'd say possibly a small vacuum leak that's getting picked up by the O2 sensor which thinks its running too lean and causing it to dump more fuel causing the HC to be slightly higher and the O2 to be slightly higher also. A leaky injector could definitely cause HCs to be higher but not the oxygen without causing CO to be elevated which it isn't. Don't take my word for it I'm just thinking out loud.

dazebreak

I'm sorry, I should have written back sooner...

The fuel injector route is pricey, so I started revisiting the smog...

It failed at idle, but it had been sitting around before they tested it.

Then I decided I needed to revisit the maintenance points that might contribute.

The oil wasn't too old, but it was pretty dirty... long story short, I changed the oil and filter, the fuel filter, put some techron from a bottle in there.

Removed the throttle body, cleaned it up, changed some seals and o-rings on the throttle body, as well as the throttle body to intake gasket.

Rechecked timing and idle.

Drove it around for a day and my girl who drives it took it to work as usual.

Drove on freeway 20 minutes to smog place, tested that morning.

HC at idle? 17

And their idle was around 1000 rpm instead of the 600 or so at the other place.