ok, my blazer is misfiring/shuddering usually at 45-65 range in overdrive, ive replaced both o2 sensors on both banks, got a new injectors, new plugs, wires, rotor, cap aand its still doing it. The blazer is a 2001 4 door with a 4.3 vortec 4wd autotrac.

 

Is the engine light on ?

 

yes it is and we ran scantool on it and it was running lean but the pressure in the line is at 60 so the pumps good and my 4wd drive lights on but its just a bad switch.

 

Shuddering could be to due to Torque Converter Lock-up....try this, when you are driving it at 45-65 and the shudder occurs maintain that speed and tap the brake pedal(do not take foot off of gas maintain the speed)lightly. If the shuddering stops it is a Torque converter Clutch problem. The TCC locks up the shafts to make sure there is no stall speed occuring.

If nothing changes then I would double check all the plug wires to make sure they are fully seated and locked on...at the distributor and the plugs themselves.

 

hmmm never thought of that ill give that a try thanks!

 

You ever get a chance to test out your torque converter?

 

yes i did and it does stop the shuddering but not every time i hit the brake though but ill ask my instructor and see what he says.

 

im gonna put additive in the tranny oil and see if it works then it be the torque converter as the friction discs are worn out

 

yep put the shudder stop additive in it and it stopped it so now we know its the torque converter!!