I have a 1991 366 cu. in BB on propane only, I have been getting codes 12,43,44. I found a broken wire to the O2 sensor, now I only get code 12 and 43. The truck hardly has power. I have a Super Fix 1 P/N 8789-6M electronic box on the system. It is supposed to prevent codes 43,44,45, 13 and 32. I have checked the wiring of the unit and it appears to be hooked up correctly. I am wondering if anyone is familiar with these super fix 1 boxes and know if there is any way to tell/troubleshoot if it is working properly? I have replaced the knock sensor, O2 sensor, ESC module, cap rotor, ignition module, wires and CTS. Manual timing says 10 degrees The pickup coil in the distributor shows 0.1 ohms to ground. Vacuum gauge does show late timing indication when hooked up. It starts and idles very good. Any more ideas would be great. Thanks..

Have you tried checking mechanical advance. I don't know much about propane, but all engines need proper spark. Do you know what codes 12 and 43 are? that may help narrow down your problem.

This HEI distributor, known as a Type 2, does not have a mechanical advance, it is all done electronically. You need to unplug the electronic advance wire to the distributor and check the timing with a timing light. Mine is sitting at 10 deg advance by the distributor. I think this is common for big blocks. 6-8-10 deg. It just seems like it is not getting the electronic advance required when trying to move? Codes 12 is to tell me that a code has been set, ie;43. code 43 is ESC circuit of which I have replaced the parts and this Super Fix 1 box is supposed to prevent this code, and advance accordingly when on propane. I have not had any experience with this Super Fix thing.

366BB, on propane, in a truck. So... Why are you on this forum again??