P0300

I have a 2001 Silverado 5.3L. 120,000 miles, it recently started running rough at idle. During cruise its fine. RMP at idle will go from 700 down to 500 back and forth, sometimes it will die. Check engine light came on for random mulitple miss fires, as well as lean condition bank 1 and bank 2. Fuel pump is good. Any help please.

I have a 2001 Silverado 5.3L. 120,000 miles, it recently started running rough at idle. During cruise its fine. RMP at idle will go from 700 down to 500 back and forth, sometimes it will die. Check engine light came on for random mulitple miss fires, as well as lean condition bank 1 and bank 2. Fuel pump is good. Any help please.


have you ever cleaned the throttle body/IAC area ??? this is a start...
what was the fuel pressure ?

sorry, my bad. pay no attention to my previous remark.
so, you do have P0300 showing?
P0300 Code - Cylinder Misfire

Technical Description

Random/Multiple Cylinder Misfire Detected
What does that mean?

Basically this means that the the has detected that not all of the engine's cylinders are firing properly.
A P0300 OBD code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.
Symptoms

Symptoms may include:

the engine may be harder to start
the engine may stumble / stumble, and/or hesitate
other symptoms may also be presentCauses

A code P0300 may mean that one or more of the following has happened:

Faulty or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft
Defective computerPossible Solutions

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the , it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

this code only,,, is common with low fuel ,,,erradic fuel pressures ,, as well as what you mentioned...normally this code has other codes,,, with the area of concern , that corresponds with a defective operation ,, if it were a non fuel issue.

First thing here is to get a fuel pressure gage on it as mentioned, 58-62 psi.

Check your intake gaskets, they are common on those.