I'm searching for everything because I have a problem that just wont go away so I want to learn everything about how my 305's ignition system works. My focus will be pretty much on the computer controlled timing and reasons of why it would change. If I had the book right now I would give you the error code but I dont have the book. The Error code points to the ESC module anyway, the Electronic Spark Control Module. I have replaced this module with an old one that came from the same year thirdgen, only difference is it being out of a Camaro and not a Firebird, but same engine.

Symptoms, after driving for quite some time the check engine light comes on and the engine looses its power. Look up the code to read that it points to the ESC (electronic spark control) All items in the book have been checked.
>The check engine light will come on sooner if these following conditions are increased... 1. Hot weather or heat under the hood. 2. If you Romp on it (excessive acceleration) 3. Car has been running then parked for less then 8 hours, heat still exists under the hood, engine not completly cold.

Car's info,
89 Firebird Formula
5.0FI 305 LO3 with TBI
>no mod work other then headers, exhaust, open element air cleaner
>rebuilt engine bought from someone 3 years ago, same issue the whole time, it was never solved. No other problems have been around to cause this one.

What I think,
A computer module or sensor heats up causing wires to connect and share electronic passage confusing the computer system as it tries to re adjust the timing to resolve the issue when in fact, it makes the issue worst.

My soon resolution,
Trial and error, find out exactly how the spark controll system operates, eleminate the most lily cause first and proceed untill the check engine light no longer comes on. I will find what causes the timming readjustment even at the last replaced componet, I WILL NOT CONTINUE TO LOSE MY HP!!! lol Thanx for the help and if you cant help and made it this far down in reading well.. Thanx for reading down to this far on the page and taking the time to do that much.