My 1997 Blazer 4.3 with 121000 consistently miss-fires at about 30 MPH. It doesn't matter if the engine is warm or cold, it will do it when I am accelerating or letting off the throttle. The good thing is it only does it the first time the vehicle reaches 30 MPH. It will perform normally until I shut the engine off and start it again. I haven't done much to fix it yet. Last change plugs, wires, rotor and cap around 99000. Thanks for any suggestions.

Could be...

- simple - timing is bad - make sure you disconnect your ESC bypass wire (read the instructions on the fan hood)
- ignition module (base of distributor)
- bearings on distributor (get one from junk yard)
- computer (doubt it)

Fix it soon

Could be...

- simple - timing is bad - make sure you disconnect your ESC bypass wire (read the instructions on the fan hood)
- ignition module (base of distributor)
- bearings on distributor (get one from junk yard)
- computer (doubt it)

Fix it soon

The 97 does not have adjustable timing.
But camshaft retard setting can be adjusted.

My 1997 Blazer 4.3 with 121000 consistently miss-fires at about 30 MPH. It doesn't matter if the engine is warm or cold, it will do it when I am accelerating or letting off the throttle. The good thing is it only does it the first time the vehicle reaches 30 MPH. It will perform normally until I shut the engine off and start it again. I haven't done much to fix it yet. Last change plugs, wires, rotor and cap around 99000. Thanks for any suggestions.

If you are getting a dead miss or a misfire.
Areas to check would be cap and rotor and wires and plugs to start with.
What kind of plugs did you use?
Have you checked for codes or run a fuel pressure check?
On the 97 another thing to check is the camshaft retard setting.