(P0300 P1153) (P0158 P0151 P0174) 1996 Chevy stock Impala SS engine

Question

I'm shuffling back and forth between these sets of codes.  The engine briefly studders/hesitates upon accelaration and I throw a misfire code during highway driving.  The dealership already found wires melted on the passenger side next to the headers..and repaired which cleared up the O2 sensor codes.. However Now I'm stuck with misfires (mostly cylinder 4 P0304).  I found the spark plug wire cylinder 4 at the distributor loose and tried my best to secure.. I also found a thin air hose that attaches in the back near the firewall to I think the 2 fuel lines... it runs from there back into the head of the engine.. I think that was my vacuum leak..I've taped it up..(haven't yet bought the replacement part but my rough idling has improved).. But I mainly wanted to find out about the P0300 / P1153.. .if it its possibly my distributor cap? All 4 O2 sensors have already been replaced.  Also is there any wiring diagrams available for this engine?  I want to systematically begin replacing my wiring harness...especially related to emissions....       Thanks in advance.

Answer 1

P0300 - Random/Multiple Cylinder Misfire Detected

https://www.autocodes.com/p0300.html 

P1153 - CHEVROLET - HO2S Insufficient Switching Bank 2 Sensor 1

P0158 - HO2S 22 circuit condition (Heated Oxygen Sensor Bank 2 Sensor 2)
The powertrain control module uses the oxygen sensor to calculate the air/fuel ratio in the exhaust.

Probable Cause[s]

1.Oxygen sensor defective
2.System running very rich or lean-check other codes first
3.Engine misfire condition-repair
4.Fuel pressure very high or low-fuel pump or pressure regulator
 

P0151 - HO2S-21 (Bank 2 Sensor 1) Circuit Low Input
 

Air leaks in the exhaust system, intake manifold, vacuum lines
Engine misfire condition present (look for P0300 series codes)
Fuel system too lean (possible low fuel pressure, water in fuel)
HO2S signal circuit is shorted to the sensor or chassis ground
HO2S is damaged (i.e., cracked) or air reference hole clogged
PCM has failed

P0174 - Intake air leaks
- Front Heated oxygen sensor may be faulty
- Mass air flow sensor may be faulty

it could be the fuel filter but it could also be a vacuum leak, at your intake gasket.