Questions and Answers

GMC Suburban Code 43 Q. I have a 1991 GMC Suburban 4x4, 350 motor, automatic transmission, fuel injected carburetor and about 130,000 miles. My vehicles problems are black smoke from tail pipe at start up, runs a little rough like its missing or something (sort of studders ?).

I did a diagnostic trouble code and came up with 43 - electronic spark control circuit. I don't know what to do with this or where to find it or if it even relates to the problems mentioned earlier.

A. The black smoke makes me think it's running too rich. Possibly a leaking injector or pressure regulator. At this mileage, I would consider a new throttle body if the regulator is leaking. The code 43 could be an ignition fault like the module starting to go. After shutdown, remove the air cleaner and watch for dripping fuel from the TBI unit.