91 s10 blazer engine stumble

I recently put a new tranny in my 91 and fixed the timing, but after that the engine light will go on and off every time i drive it. It runs crappy when the lights on and then when you let off or part throttle the engine will stumble like its about to die. if any one can help i would be grateful because this issue is about piss me off.

Welcome to Automotive Forums :cheers:

Have you tried a full tuneup?
If not that's the first place to start
Basicly follow the list on this page
http://www.automotiveforums.com/vbulletin/showthread.php?t=453370