Alright, I have an '89 Trans-Am with a 350 TPI. I had the PROM reprogrammed and long story short, all the engine management numbers off the computer now are wrong compared to whats actually going on. The O2 is reading normal according to the computer but in reality is running rich. The coolant temp. reads 100 degrees always, and when you dicsonnect it it doesnt read the default -40...stays at 100.

Here is my question. Is it more likely the PROM programming or the ECM itself? I havent broken in the piston rings on this engine yet and running it rich like it is isnt the best idea to break in rings. I was going to throw a stock ECM/PROM in there for a 305/350 just to break the engine in if I could but wanted to know if this sounded like PROM issues or ECM. Maybe I could just get a stock PROM out of a 350 instead of the whole ECM...only reason I ask.

Second question, I know the PROM is different from 305 to 350, but what would be the most likely result of using a 305 PROM in the car to break it in? Run rich/lean...by a lot? Could I get away with it just to get some miles on the car and get everything broken in and seated properly? Or do I have to get a 350 PROM as the 305's will kill the new motor. Ive heard that it will run close enough unless your running it hard...but for break in the 305's should work. To be honest, anything will be better than what its reading now...basically its running in default rich mode right now.

 

Double check the engine grounds on the back of the head(pass side)

Also try plugging in the other memcals and just go key on and see if anything changes.

I havent seen too many failures on 165 or 730 ecm's unless you have bad injectors and in that case it usually fries the injector drivers. Not saying it isnt possible just not the usual suspect.

If it makes no change with it connected or disconnected have you checked the wire from end to end(continuity) and one for 5volts and the other for ground. Also test the ohm reading of the sensor itself.

Also improper offset in the chip or memcal/chip with porr contact can also cause all manners of fun issues.

later
Jeremy

 

Grounds are good...triple checked them :-p I guess I will pull the PROM and make sure its properly installed. I dont have a spare PROM with stock setting so I have to get one and try swapping them after checking the memcal placement.