91 honda civic dies at low rpm is running on all cylinders runs smooth at higher rpm could it be oxy. sensor?

Question

engine will also backfire through carb

Answer 1

most likely a hung EGR valve if the problem is under 2000 rpm and smooths out over that engine speed.  A hung egr valve would flood out the engine with air and  lean out the fuel mixture and cause the engine to have very little power until you got up over the 2000 rpm when the valve is normally open.  it would also cause a lean backfire.

Any unmetered air could cause this condition so check fo vacuum leaks from any and all of the rubber hoses.  make sure the carb base is tight and that the gasket is not leaking.

It would not be the oxygen sensor.

you also want to check the ignition components--distributor cap, rotor, wires etc. and make sure the fuel filter is not restricted as those could also cause the lean backfires.

hope that helps

Answer 2

honda guy is most definitely right, an EGR valve can make your vehicle run crappy at bottom end. My truck does it too, and when I clean out the EGR valve, it clears up for a while.