On my wife's 98 the code started coming on and off for sometime know with a few times not wanting to turn on. The code would leave and come then finally this past tuesday it was time for a tow truck. She would turn over but that was all, fuel was good, had spark but it sort of looked like a weak spark. Just for the hell of it I swapped out the coil and the module with spare ones that I have and still no good. Took a shot at the cranksensor thinking maybe it was not sending a good signal and still the same. Took the cap off and it looked pretty dirty so got the spare one in and then I noticed the rotor was bad. The center of the connecting probe had cracked completely off. Put in the spare rotor and thank god she turned on and was very smooth. Took for a drive and great, yesterday my wife was driving and the P1351 came back on and then cleared up. Where else should I start looking at. Any help would be highly appreciated, thank you.

 

This would be an excellent place to start: https://blazerforum.com/forum/diagno...plained-35134/

Follow the steps in the flow chart, it will take you to the problem.