Civic VX Federal (original) wont pass CA smog

[wollbs]

Greetings all,

I have a federal '93 civic vx that runs well, but is not passing smog (it did 2 years ago)..see attached smog levels. Any suggestions for troubleshooting? It was running rough over the summer (lugging at low rpms) , so I did spark plugs, dist cap, wires, and adjusted the valves. This smoothed out the drive considerably...could the valve adjustment have caused the change in smog levels? There is a range of adjustment,....but what is ideal for smog purposes? Both of these smog reports were after the tuneup-->. The only thing changed between tuneups was the 5-wire oxygen sensor.





Thanks so much,
brandon

[wollbs]

One more bit of info: Check Engine Code 48 was in the history..prompting the o2 sensor (NTK) switchout. I have not seen the check engine light since (I dont remember seeing it the first time...but that was on a diagnostic note from mechanic.)
Thanks again,
b

[Patrick]

Have you changed/cleaned the air filter?

You also might try a catalytic converter cleaner.

I used to run the fuel tank down to a couple gallons of gas then add 91% isopropyl alcohol (2 pints, available at your local drug store for a couple bucks) to the tank and drive around for about a 1/2 hour before I went in for my smog checks. At that point the car was making oxygen. This may not be legal where you live, so check the law first.

[Ladogaboy]

It looks like you are running VERY lean. That might actually be a fuel delivery problem.

[wollbs]

Originally Posted by Ladogaboy

It looks like you are running VERY lean. That might actually be a fuel delivery problem.

Thanks for the response...Which numbers suggest that it is VERY lean? Could my valve adjustment have caused it to run leaner?

[wollbs]

Originally Posted by Patrick

Have you changed/cleaned the air filter?

You also might try a catalytic converter cleaner.

Thanks for the reply. Yes Air Filter is changed. When you mention catalytic converter cleaner, and then talk about isopropyl...were these the same thing, or two different suggestions?

[Patrick]

Originally Posted by wollbs

Thanks for the reply. Yes Air Filter is changed. When you mention catalytic converter cleaner, and then talk about isopropyl...were these the same thing, or two different suggestions?

Different suggestions. The cat cleaners are usually petroleum based.

[jakobnev]

Originally Posted by Patrick

The cat cleaners are usually petroleum based.

I think they might contain a splash of unicorn liver oil too.


Worth knowing is that a sensor fault code doesn't have to mean that the sensor is broken, it only means that the ECU doesn't get the signal it expects from it. This can have many causes.

When's the last time this car got a new fuel filter?

[user removed]

Unburned HC means fuel that has not been completely burned in the combustion process.
Potential sources of incomplete combustion are many.

Fuel injector spray pattern bad.
Ignition signal-spark marginal
EGR system not functioning properly.

Ignitors are common problems.
Clogged EGR passageways also common.

Before you embark on what could be a complicated process, I would try either sea foam or having the injectors cleaned and balanced. Plugged EGT passageways in the intake manifold are common enough to actually be a maintenance process, meaning do them at any mileage over 120-140K even if an issue is not detectable.

Typically when EGR is low you get a high CO reading so the injector clean-balanced flow may be your best first step.

While a fuel filter is good maintenance it will not affect emission readings unless it is really plugged up. Then it would act as a governor, only allowing a certain level of load to be applied to the engine before it would not produce more power.

regards
Mech