Has anybody ever did a car that was 1991 tbi 305 to a maf tpi set up? I got 1988 ecm and harness under the hood but have fes bugs. No guages or NON FUNCTION ADAL PORT. I get a checj engine light under a load and have no clue because cant read with a scanner. But a and b work because we jumped then to reset the idle air motor.

 

Your ECM shouldn't affect your gauges. The gauges work off separate sensors on the motor. When you short A&B, what codes are you getting? What kind of scanner are you using? Is pin E or M populated on your ALDL connector? I think TBI cars use pin E (160 baud) and TPI cars used pin M (8192 baud). Let us know what you find!

 

i have done the 92 s/d tpi conversion to my 91 tbi and other than a speedo issue everything works fine.
i did a 86 maf tpi to an 88 carb that once was tpi. that was a mess. it is possible if you are not the original owner of the car, that the underdash harness has been modified or altered. i would get schematics or diagrams of the original underdash harness and go from there

 

1991 with 89 maf system. Had to move a few wires around in the c100 and c207 but other wise ran fine for years.