Regulatori

First questions.

My 93 C2 gets horrible gas mileage. Yeah, I tend to have a lead food but I'm averaging around 10-11mpg with a mix of freeway/city. I originally had an FVD chip and switching over to a Steve Wong but have the exact same results. I have a feeling it may be my 02 sensor...is there an easy way to check if it's functioning properly?


Second question...
I'm running an FVD exhaust that has no cats. I recently got it emission tested up here in Washington State and it passed HC/PPM with flying colors but failed the CO%. My results were...
CO% Cruise Limit: 1%...my car was 1.23%
CO% Idle Limit: 1.2%...my car was 2.60%

Do you think temporarily swapping out the Wong chip for my stock/OEM chip would improve my CO levels?

I did run my car hard for 30 minutes so the engine was nice and hot...it definitely wasn't that.

Thanks.

Makmov

If your check engine actually has a bulb in it and it works the light will come on if your O2 is bad.

However, there is a good chance the bulb has been pulled, because even when the O2 is working correctly the light comes on sometimes for no apperent reason and panics the owner into thinking it more serious. The only other circut the MIL or check engine light comes one is with an evap error. It is a pretty basic system.

A bad O2 will also acount for some bad mileage, but I am not sure about horrible mileage.

Another indicator will be the car will be flat up to 4000-4500 rpm and then go like stink.

A car with a good O2 will be much more even throughout the entire range.

However, I am not sure but I don't recall a bad O2 making it rich at idle just the upper RPM ranges will go rich. There could very well be another problem.

I am surprised they allow you no cats?

Regulatori

I definitely know my CEL works because I it used to pull a random code due to a dirty throttle spring.

I can't figure out the mileage issue. I try to stay under 3K RPM, only do few blasts (usually on the freeway onramp) to clean it out. My calculations are correct.....I usually average around 50-60 miles per 1/4 tank.

Washington doesn't do a visual inspection and it's common to hear people passing with no cats.

J richard

My suspects for poor mileage would be, provided it is regularly serviced and isn't due, in order:

1. Vacuum leak- breather line, oil cap seal etc...
2. One or more injector
3. Aux air valve

964s tend to run dirty w/o cats mine wouldn't pass smog without it...but you will have no chance if one of the above is an issue...

-nick

Not a 100% on this, but I believe an o2 sensor can slowly die and not trigger a check engine light. How many miles since it's been replaced, if ever? Older o2 sensor lifetimes are something like 60-80k miles. The sensors are neither expensive nor very difficult to replace.

J Richard has a pretty good list of possible culprits too.

Makmov

Could be a leaking injector, but the other symptom of that is hard starts when it warmed up.

Does the CEL light come on ever?

Regulatori

Thanks for all of the help.
The only time it has issues with starts is if it's an especially cold night and I had to park outside. It just takes a bit of extra gas for 10 seconds after startup to keep it running..and then it's fine after that.

I believe the O2 is original and the car has 75K miles. I was going to try another emission test but I'll wait until next week when I have to bring my car into my local mechanic to fix an oil tank hose leak and replace the distributor belt. I'll have him check the O2 sensor (and replace it) and various other things (vacuum leaks, injectors etc..) to see if he can find a culprit. Thanks.