Hi my name is mike im new to blazer forum so i really dont know too much about blazers so let me get you guys started by telling you that i have a 1995 4dr 4.3 vortec cpi. I bought the truck from my relatives the truck was sitting for about 7 months. Idrove for maybe 2 days and the cel comes on. So i figured it needed a tune so i bought plugs and wires. I gapped acdelco to .45 and bought xact wires from advanced auto along with cap and rotor and i went through hell trying to find a cap and wires because it is a horizontal mount. Before i went and bought all of this i went to advanced and had then put the obd on it they came up with these codes p0141 o2 sensor heater circuit malfunction-p0172 running too rich bank 1-p0300 random/multiple cyclinder misfire-p1406 manufacurer control auxiliary emisssion controls. So after i put plugs wires cap and rotor i went and replaced the o2 sensor on bank 1 sensor 2 .the cel went off for 2 days and came back on now. also the gas gauge acts funny when i take off the gauge moves up and stays up but when i come to a stop or just sitting there idling the gas gauge go to i guess the normal reading. so i really dont know how much gas i have until i stop. also it run kinda ruff sometimes the oil pressure will drop from 40 to 20 outta nowhere i have reset the computer a few times to clear the ecu but the light will come on after a day or so maybe 60 miles or so. Can somebody please help me

 

P0141 - HO2S Heater Circuit Bank 1 Sensor 2
P0172 - Fuel Trim System Rich Bank 1
P0300 - Random/Multiple Cylinder Misfire Detected
P1406 - Exhaust Gas Recirculation [EGR] Position Sensor Performance

The P1406 is possibly causing the P0300 code. It could also be the reason for the P0172 code as well. I recommend you remove the EGR valve and give it a thorough cleaning with some sensor safe carb cleaner. Replace the gasket with an updated gasket which has an integrated screen. Reset the PCM and see how things go.

The P0141 code deals with the B1S2 sensor which has no bearing on fuel delivery, only emissions monitoring. You can swap the B1S2 (directly ahead of the catalytic converter) and the B1S3 sensor (directly behind the converter) and see if the code follows the sensor. If it doesn't, then you may have a problem with the wiring leading to the sensor. If it does, then the sensor is bad.

On the oil pressure, so long as it doesn't drop below 10psi, you are fine.

 

i also forgot to tell you that i did take the egr off and cleaned it very well the problem still exsist and replaced the o2 sensor behind the cat another question is there 3 o2 sensors or only 2