First some info on the car: a 1990 Firebird Formula that was originally an LO3 car which I swapped out the TBI for TPI. I'm using a Walbro 190 lph pump with Racetronix hotwire kit and a stock '91 PROM with a Moates adapter to correct for 22# injectors and to disable the a/c request signal and the AIR system. First problem is that I can't pull any info from the ECM with my scan tool. Now granted it's an older Actron unit that read the car fine when it was TBI and reads my brother's '94 fine but won't read mine now with the TPI. The ALDL was checked during the conversion and I can pull codes through the SES light just fine but I'd like to see what the ECM is seeing when the car is running. The other "problem" is that the car seems to be unable to hold a long term memory. The car is not a daily driver and only comes out on weekends and for shows/cruises and such. If the car has sat for a week and I go to start it it will run for around 4-5 minutes with what I will call a rough idle (some would think a large cam was in there). After the 4-5 or more minutes it will idle up 2-3 times and settle into a normal idle which I'm pretty certain is indicative of closed loop mode. All power connections have been checked and there are no missing connections. The car runs great otherwise. The car also has a heated O2 sensor which leads to my last question: what's the potential life expectancy of a heated O2 sensor? I've always used Bosch with great results but I've had to put replace it twice in the past 3 years with one of them being since the TPI conversion in November '06. Any help would be appreciated.

 

Are you burning your own chips? If so, do you know which you used for a starter bin and where you got it?

 

No, I've not ventured down that road yet. The adapter was purchased from TPIParts. I gave Angel the 4 letter code on the PROM I'm using and he made the changes I previously listed.

 

There's a modified bin file posted on the net that causes the exact same symptoms you describe, being able to pull codes and the engine running fine, but not being able to datalog. Its for a manual equiped camaro. So i dont think your chip burner would have used that one. But who knows.

 

I've been considering swapping the 22# injectors out for a set of flowmatched 19# units and removing the adapter to see if it improves. Lowering the fuel pressure has helped some as well. I can safely rule out the ECM as the problem as well as I've recently replaced it chasing another issue and the current symptoms still exist. I'll be replacing the O2 sensor this weekend so hopefully that will help. As for the Actron unit I've been told that the newer units have no problem reading the TPI computers and that the one I was using is too old, but why will it read a '94 LT1 then?

 

Did you change the pin at the ALDL connector? The '8746 and '7730 ECMs go to a different pin. IIRC they are E and M, not sure which ECM uses which pin.

RBob.

 

Tried that as well, still wouldn't read the data.

 

And just to be sure of what you recommended I recompared the ALDL layout for both TBI and TPI in the GM Service Manual for the 1990 model year and they are both identical with "E" and "M" in the same locations. When I first ran into this datalogging problem I swapped their locations but it still wouldn't read. Right now I'm suspecting the PROM adapter is somehow causing this (don't ask me how), maybe 884+3 is on to something. Plans are to remove the adapter and see if anything changes this weekend.

 

Well, got the troubles resolved. Turns out the ALDL problem was due to incorrect wiring on GM's part. The serial data wire (CKT 461) is supposed to connect at both pin E and M according to GM Service Manual. Mine only had it at pin E and a tan wire at pin M (never did find where it went). After probing all the ALDL wires back to the ECM connections the solution was to tap into the wire to pin E and connect it to pin M's wire which allowed the scan tool to read everything that was going on. After replacing the O2 sensor the car's poor running didn't improve, I then removed the PROM adapter from TPIParts and the car was a totally different animal. Idle was smooth, throttle response is back to normal and all readings from the scan tool are right where they are supposed to be with exception of the BLM near 150 but that's not making sense. I would think that with 22# injectors on a 305 it would be trying to lean the car out but if I'm reading it right it's trying to add more fuel. Anyone got any thoughts?