I have noticed that every day when I start the car, the first few minutes or so are when it runs the best, seemingly when it's still in open loop. Even when I let it sit for 3 or 4 hours it still does this. What gives?
The o2 sensor was replaced recently, although it had a bad encounter with the frame when I was putting in my headers (got a big dent in it). But I know it works, I have tested to make sure it goes into closed loop and it does after a min or two.

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White '92 Firebird w/ 305 TBI. Open element w/ non drop base, increased fuel pressure, TBI spacer, Hedman Hedders & y-pipe, no cat, cat-back exhaust

 

Tab,

What you are experiencing is the fuel enrichment and extra timing advance that occurs at lower CTS inputs. this is one of the main reasons most of us try to keep our coolant around the 180° F range or slightly below. The other reason for lower coolant temperatures is greater engine life.

Maybe you should be thinking about a different thermostat and/or custom PROM programming.

Later,
Vader

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"Some Body...Someone"

 

Well, I forgot to mention that I have a 160 degree stat and I now have a fan switch. I usually run a hash mark or two below the 1/4 mark.

 

Tab,

That being done, and having adequate fuel pressure for your intake improvements, the next item to check is the base timing. You may be able to sneak in a few more degrees of advance to take better advantage of your cooler heads.

Beyond that, and understanding that your TPS is non-adjustable, you may be looking at reprogramming. GM just about took all the fun out of tinkering with the fuel system with speed-density and fixed TPS. Enrichment and timing advance offsets are generally higher in open loop, and I don't know of a good way to "fool" the ECM on an SD system.

One other thing to note is that the EGR and EVAP are not at 100% duty cycle until the ECM is in closed loop and the coolant is above 170°F. You might want to experiment with that in mind, too.

Later,
Vader

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"Some Body...Someone"

 

Thanks for your help, Vader.
I have done the afpr mod, and I have the fuel pressure quite a ways up (at least I think I do...). I know in a tech article it speaks of using a digital multimeter and the O2 sensor to test my fuel enrichment, but in my chilton's it says that any current draw on the sensor will damage it...is this true?
Also, since it feels like the car runs better (because of more fuel enrichment and timing curves, like you said) in open loop, could a chip somewhat correct this problem? I'd ask what is recommended, but I can always look at the archives.
btw, the base timing is set to 7 degrees.

Thanks,
Brandon

 

Changing the Thermostat without having changed the chip is a big mistake especially with TBI. I have seen so many people think it will do so much for them, yet changing this will play games with the ECM because it is expecting a 180* or 195* thermostat and the EGR and EVAP will not work until the coolant hit 170* so it will go in and out constantly. Try a 180* if you want to stay away from a chip.

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1987 Firebird Formula
305 LG-4
Crane CompuCam 2030
700-R4 Trans
4 barrel quadrajunk remained by holley (this carb stinks!!!)
edelbrock performer intake
Hypertech Thermomaster Chip
Open Element Air Filter
No Cat with Straight pipe (Dynomax muffler rusted apart and fell off)

- Soon to be installed
Holly Spreadbore 600
Edelbrock TES
True Dual exhaust or 4 inch single pipe to dual 2 1/4"
Accel H/P Coil
1.6:1 Ratio Rockers
Set of New Valve Springs