"99 Blazer 4.3, manuf. control ignit. system or misfire

[sunnygrl027]

we have a 99 4.3 blazer, 147,000mi, bought used after sitting for about a year. ran fine to begin with, now it has a major misfire/sputter/hesitation when accelerating, check engine light comes on at random.

my husband has replaced the crank/cam shaft sensors, egr valve, fuel pump, distributor, rotor button, thermostat, plugs and wires. still same problem, now some when idling.

computer shows "manufacturer control ignition system or misfire". he's wondering if it could be the timing or O2 sensor, and if not, what should he check/replace next?

pls. help! he's getting frustrated and he's talking about selling my blazer!!!

[ls1s10onair]

i believe there was a service bulletin about faulty distributors for that vehicle (for excessive play i believe).... there is no timing adjustment .....