Conaswr

Is there an easy way to adjust co2levels, my cat is in place and car was warm but went over co2 levels for emission testing. 86 cab no mods.

Thanks for advice

J. Brinkley

put up your other numbers to, o2, nox, co, hc
that way someone can help you out

J. Brinkley

maybe this is all the help you need

glenncof

I have an '85 Cab in California. Here we do dyno smog testing which is tough. I looked at this chart with all of my smog records trying to anticipate failing my first dyno test last time. As I understand all fuel/air mixture is set by the ECU and is not adjustable on '85/86.

I did replace was the oxygen sensor. It is rated to last 60K miles. I had been passing the non-dyno testing for 10 years even when the O2 sensor was probably long dead. With no O2 signal, the ECU reverts to preset which in my case was ok. So consider replacing if > 60K on it.

High CO or HC seems like fail mode, CO2 should be peaking per above chart.

Dirty injectors (use Techron per porsche) or dirty Mass Air Flow sensor wire could also do it (K&N air filter?). There is also an engine temp sensor that went from a 1 to a 2 wire upgrade (or something like that), check ohms per a service manual. I would only replace is out of spec.

Peter Zimmermann

The adjustment should be performed by a knowledgable Porsche technician. The adjustment is a specific procedure and requires a CO% machine that is accurate to 0.1%. I might offer that in most cases when CO is too high the air flow meter is at fault, but your technician should be able to do that diagnosis while setting the mixture. The above mentioned 1/2 wire sensor is the cylinder head temperature sensor, and my recommendation is to upgrade a single wire unit anytime that the engine is out, where access is easy, or during a routine, high mileage service. In other words, replace it before it causes a big headache, not after.
Pete