Passed Smog Test, but what do the numbers indicate?

[HKforte]

Hey guys,

I failed my California emissions test a couple times with High CO, then I did a carb rebuild myself and finally passed smog. With the numbers below, I think I barely passed. My 1978 40 does run well and is a daily driver, but I'd like to know if the numbers indicate any issues with the rig that should be fixed. What do these numbers mean and what can I do to improve them?

My timing is currently set at 9 degrees BTDC and I'm running a stock distributor with an advance and retard unit. I recently fixed a crack in the intake manifold, disabled the heat riser, placed an insulator between the intake and exhaust manifold, adjusted valves, but I do have a slight exhaust leak due to a bent exhaust flange that connects to the manifold. I'm also pulling steady vacuum at 18 inHg at idle.

Thanks.

 

[Mr. Toad]

Running a little rich (high hydrocarbons and CO). EGR looks like it's working (good NOx #s).

Does it stink?

 

[Flash1034]

If your Cal spec 78 is like mine, your distibuter is a vacuum retard type. FYI

Flash

 

[HKforte]

yes, I believe I'm running a little rich, but when I would lean out the mixture my HC level would go even higher.

 

[Mr. Toad]

yes, I believe I'm running a little rich, but when I would lean out the mixture my HC level would go even higher.

Could you be too lean, and the high HC (and CO) is from the mixture not firing in the cylinder?

 

[Flash1034]

I doubt it would have passed smog with a misfire or dead cylinder. The numbers look OK to me. Whats the problem?

Flash

 

[Buckwheat]

Emissions I/M

Your mixture is rich but legal, so, like the man said, why worry? The rich mix if leaned with bring all numbers down, until it gets too lean. Backing the timing off only will reduce HC, but you are only allowed 3 degrees either way, max. The CO readings are hardest to change but sometimes putting in a fuel pressure regulator will help, if fuel pressure is keeping the needle off the seat & allowing excess fuel into the mix. I always decarbonize the cylinders before a smog test to reduce potential cylinder hot spots & high NOX. Air injection could also be problematic, based on your high numbers across the board, & that is always supposed to be the first place for the technician to look for a problem. At any rate, you have 2 years to work on it.

 

[Pin_Head]

HC generally comes from either misfiring or from exhaust valve blow by. CO is incomplete combustion from a rich mixture, but at 15 and 25 MPH, it is not due to the idle mix, which is the only one that is adjustable. Make sure that the power valve line has vacuum on it or it will run rich at all speeds.

 

[HKforte]

I was also thinking my issue is due to air injection. How much of a bearing would the adjustment of valves have on this issue? I adjusted the valves by the book, several times, but I'm thinking that they may be too tight?

My float needle was leaking fuel and flooding the carburetor when I was failing smog, but I put in a new needle and float. Now the fuel level in the carb window stops a little above the halfway line. It doesn't have to be exactly in the middle, does it?

I installed a catch can between the PCV Valve and the intake manifold to see how much blow by I would catch. I've noticed that the can fills up with about 2 to 3 ounces of black oil, every 400 to 500 miles.

 

[Pin_Head]

A leaky/tight exhaust will cause a big increase in HC. Your numbers are very close to normal, so there is nothing to worry about.

 

[HKforte]

Thanks guys. If it ain't broke don't fix it, right? I often find myself looking for problems that don't exist and I break stuff on the cruiser in the process