Looking for ideas and input. Own a 1997 ZR2,4.3 new factory replacement engine about 3 years ago. Have also done the following work, 2mos ago rebuild on the transmission, new injection spider and upgrade, new fuel pump and regulator, all new O2 sensors, new plugs, new wires, new cap rotor, MAF cleaned as well as throttle body, and the dizzy was changed with the new engine.
Truck starts and runs fine until I get to freeway speed it bogs, misses, and if I accelerate to pass someone it backfires and just runs poorly. Never throws a code or triggers the check engine light.I feel I've tried it all, any ideas or solutions would be appreciated....


Jim

 

Fuel pump, cap, rotor and plugs need to be AC Delco. If not, you did very well getting 3 years out of them


If the check engine light is not coming on, the problem is something that the OBDII doesn't monitor. Here's where to start looking: https://blazerforum.com/forum/2nd-ge...eakdown-88305/