When my problem started, it only happened when the Blazer was cold and usually only durring the first start of the day. It would stumble at low speeds (5-20mph) like I was hitting the gas and then stomping the brakes in rapid succession.

After a while it got worse and started doing it all the time. I changed the O2 sensors, MAF unit, fuel filter, and checked every fuse, wire, connector, and vaccuum hose.

This seemed to clear it up for a while but it just started to do it again very slightly like when it started originally. Any Ideas?

97 Blazer LT 4x4
4.3L, Automatic

 

When was the last time that you did a full tune up? Plugs, wires, cap and rotor?

Does it do this more when it is damp outside? If it does, then this could indicate a fouled cap as the more humid air allows the spark to scatter more when it jumps from the rotor to the terminal in the cap before travelling down the wire to the plug.

 

I think it was about 2 years ago I did the tune up on it. I changed everything.

It did do it more when it was damp. I'll check the cap once I figure out my major electrical problem...something is shorting out and wires are starting to burn. And every light and buzzer in the truck goes crazy when I try and start it.

 

besides the tune up, including a new fuel filter I would check out the cat too. A partially plugged cat will cuase too much restriction for low rpms, while higher rpms can still push past the restriction.