I have suspected that my 91 rs 305tbi has been running rich. Exhaust smells a bit more than I'd like. Completely stock car.

I have rebuilt the TBI and put new injectors in(made sure to get the right ACDelco injectors for a 305). Chased as many vacuum leaks as I could find. It's muchbetter but still running rich in my mind. I bought an ALDL cable and plugged her in. Logged my commute to work (about 10 minutes).

The log shows the :Rich Flag: being triggered on and off the entire time, about every second or two. No error codes, the o2 sensor (new unit) seems to be all over the place from .004 volts to .850 volts(maybe this is what triggers the rich flag?). BLMs and INT are both around 128 +/- 7 or so the whole time. I attached the log in the hopes that someone could shed some light on how it's running or any glaring issues. Thanks so much everyone.

P.S. What the hell is "Old High Gear Flag?" Yeah the 4th gear is about 40 years old at this point, I know....

I attached 2 files, one is the raw text, the other is converted to excel.

 

Just curious do you know how a o2 works ?

 

From my understand, it's supposed to go up and down to keep the air fuel mixture to stoich, but I am not completely sure.

 

Not really a fan of winaldl but if your o2 is swinging and when the flag happens with or reading on the higher side of .450 mv it’s rich for that swing only if it’s lingering above .450mv for a extended time. Tunerpro rt you can see the o2 and graph with $61 adx. Since you’re saying int/blm are 128 it wouldn’t appear it’s rich. Have you done a plug read since your thinking it’s rich or getting poor fuel economy that’s making you believe it’s overly rich?

 

So I took at look at the excel file...

O2 is bouncing around normally... you want it to be oscillating back and forth, indicating the ECM is continually adjusting trying to keep the voltage centered around ~.450V.

BLM and INT look pretty good. But that's only looking at the driver side where the lone O2 sensor is mounted.

If you have some sort of issue on the passenger side (bad spark plug, bad plug wire, etc), you could have a poorly burned mixture going out the exhaust. But the ECM won't react to that since there's no O2 sensor on that side.

 

Thanks, I would not have thought of that. I'll check everything on the passanger side.

 

This is the issue. The majority of the time it is a mechanical issue due to aging parts. If you still have your vapor canister connected, inspect it for leaks. Check for any hairline cracks in the fuel lines from the tank forward not just the engine bay, and make sure your fuel filter isn't leaking at the saginaw fittings, the slightest leak will produce a raw fuel smell without effecting air/fuel. Pull the plugs as well, check to see if anything stands out indicating an issue with a valve seat...

- Rob