A few years ago I bought a 89 Camaro TBI automatic for the motor for my 86 T/A. I pulled the engine and wiring harness from the Camaro and installed it in my T/A. I only modified the wiring for the headlights, tailights, and pins for the instrument cluster to make it work in my T/A. The engine wiring etc is all 89 Camaro.

Now I got the car running but when the car is cold and running in open loop, the car runs very poorly. Once it hits about 170 degrees or so, it instantly runs perfect and has tons of power. Its seems as soon as it hit closed loop it runs perfect, but until then it wont accelerate, stalls, etc.

Now before I installed the engine I took the oil pan off to inspect it and notice it was a 4 bolt, looked further and found out it was in fact a 350, but still has the TBI. Now from what I have seen the Camaro did not come with a 350 TBI, so I am thinking the long or short block or possibly the whole engine was changed. I do not have the numbers off the engine so I am not sure what it is out of. The internals also appears to be fairly new, and poss freshly rebuilt. I have nothing further on the internals so not sure what was done in there is anything at all.

Now I checked the Temp sensor for the ECM and the map sensor and they are working fine. I do not get any check engine light at all when it is running, except once and it gave a lean fuel indication.

So my question, after all this, is could the ecm/prom be causing this? What I am thinking is that since in open loop the ECM/prom is set to supply enough fuel for a 305, could it not be supplying enough to run the 350 until it warms up and starts taking the reading from the O2 sensor into account, thus giving it more fuel? If so, what is my solution to resolve this issue? Custom Prom? Different ECM? I have a 89 K1500 that also has a 350 TBI but has a manual trans and the ECM service number is off by 1 number. It is 1227747 and the ECM from the Camaro is 1227746. Is it safe to try the ECM from that truck on that motor to see if that solves it with different service numbers?

Thank you in advance for reading this and any assistance.