[:@]1992 Chevy k1500 4x4 350 auto
When slowly pushing the gas petal and standing on the brake the rpms start to decrease, like it is going to stall. But then is picks back up.. Up and down up and down... Also when not under load it feels like it “skips” when easing on the gas…
Higher RPM and speed truck runs fine.
Truck has 171k miles, temp seems normal. I have already changed the following:
Cap, rotor, wires, plugs {I gapped them} EGR, TPS, PCV, Air filter, Fuel filter, fuel sending unit and pump, TBI base gasket, fuel injectors

Question will a bad O2 sensor cause this problem?
Any other ideas?

Zamaro

 

sounds like a restrictionin the exhaust, like a crushed pipel/muffler from wheelin. im thinking it could be an intake leak too.i would use a multi meter and test your o2 sensor, if for no other reason just to rule it out.

 

The symptoms you describe are commonly associated with the engine fighting to keep the air/fuel mixture in the correct range, given poor inputs - often that poor input is in the form of a failing oxygen sensor, but it can also be a result of poor fuel system pressure, clogged injectors, restricted airflow, etc. I see you changed the fuel pump, air filter, fuel filter and injectors, soHOPEFULLY those items are ruled out.

I would most definitely test the oxygen sensor first to rule it out (that actually would have been the first test I would have performed given these symptoms, right after changing the fuel filter if I was unsure of how long it'd been in there). Here's a couple of pages describing how to do that if you not familiar with it:

Testing Oxygen Sensors
O2 Sensor Info/Testing

If the O2 sensor tests fine, I'm fresh out of ideas, as you've already changed the fuel pump (and that would have been next on my list after a fuel filter)

So to directly answer your question, YES, a bad O2 sensor will DEFINITELY cause these symptoms.