We have a 1998 Blazer (4.3l V6, 4x4, 4dr stock) that developed a problem a few days ago.

When the vehicle is traveling around 60km/h, the vehicle lurches forward at a rate of 1 lurch a second. The lurching happens on flat ground and inclines, when the drivetrain is under engine power.

No recent maintenance has been done on the Blazer recently (last major work was in the summer - the fuel pump and filter was replaced; the distributer cap and rotor was replaced when the fuel pump died...) the vehicle did produce a P0147 (rear O2 sensor heater) about the same time the lurching started (Code was cleared, but no work done - code has not reappeared yet)

Does anyone have any ideas what to do? Only thing I can think of is to change the plugs, as I have not done that yet.

 

what is lurching?

 

The torque converter clutch will just be starting to enter full lockup around 40MPH (~64KPH). You may just be in that region where the torque converter is locking, then unlocking, causing the 'problem' you are experiencing. If you lightly tap the brake, does the 'lurching' subside for a bit?