I have a 91rs 3.1 v6 that would start, run, no codes, as soon as you crack the throttle it would die. Things I checked before replacing ECM, Fuel Psi., timing, coolant temp. sensor., Tps, Iac Solonoid, Things I just replaced for GP because I got this Car from a junk yard, Ing. Module, Dist. rotor and cap cleaned rust off contact points under rotor, Plugs and wires, fuel filter, drained and filled tank 5 gall. prem., found a lot of play in the chain and changed it both gears and damper, fuel psi would not drop after starting changed fuel psi. regulator fine now and found one bad injector mine all read 11 to 12 ohms. but one, book says anything below 8 is bad. New Cat and clear pipes/muffs. Even got a code 13 once and changed O2 sensor and found knock sensor wire disconnected and hooked it up. So now after all that no change but as I read in the book I found a line that said that in the event of a ecm failure the cooling fan goes on to save from over heating. Bingo as soon as the car came down off of high Idle from cold start the fan kicked on. so that left me to thinking is it the ECM or Chip. I guess you have to think about the two like this when your dealing with them, Chips are the brains and the ECM is the body and the body is what more often gives out first, so I'm so glad this one did'nt have DE DE DE also.

 

I had a similar condition when I got my car - it ran rich as hell, and the fans would stay on all the time, but the SES light never came on. I found out that the SES bulb was burned out, replaced it, and still no codes. I also couldn't get any diagnostic info using WinALDL. I replaced the ECM with a junkyard one, and that time the SES light would flicker randomly, but I could get readings with WinALDL. The sensor values it showed were all wrong and messed up, so I replaced the ECM again with another junkyard one - and that finally solved it. I knew the 86-89 TPI ECMs were trouble-prone, but 2 bad ones in a row surprised me. The third ECM (the one I'm running now) came out of an S10 blazer with the 4cyl engine.