ourbabyq07

Hello,

We have a 1995 Chevy S-10 blazer with the 4.3l vortec, code "w" v-6 engine,with 193,000 miles,
The truck began to run erratically and lost all power and can barely get out of it's own way.We had the vehicle tested on a scanner and it pulled a code PO300,random misfire in multiple cylinders.But no one can suggest a reason for this code,or a possible solution.
Since then we have replaced the rotor and cap,plugs,a new MAP sensor,a throttle positioning sensor along with doing a stethoscope test to listen for any vacuum leaks,which there wasn't any.the vehicle has also had a new fuel pump and fuel filter installed within the past 3 months or so.
We have spoken with a knowledgeable worker at Auto Zone and he suggested that the fuel injector/fuel spider was bad but the vehicle has not set a trouble code for this problem. I have also spoken with a friend that said that his similar problem on a 1992 Pontiac Sunbird was resolved after replacing the MAP sensor,the IAC(intake air control) valve and theTPS sensor.Since we are about broke and frustrated with purchasing parts to no avail,could anyone have a suggestion as to why the PO300 code would be being set by the computer.
I would also like to add that each time a new sensor has been installed,we have disconnected the battery to reset the computer to recognize the new part.I would also like to add that the truck will run sometimes,but the engine surges and idles extremely rough.
When sitting in park with my foot on the accellerator holding it at 1000 rpm,the engine will surge between 1000 and 1500 rpm,
Could we be experiencing a problem with a fuel pressure regulator problem or worse the entire fuel injector assembly?
Please help if you can.
Thank you,
Jerry

old_master

If P0300 is the only DTC you're getting, the other sensors are more than likely working ok. P0300 can be caused by secondary ignition faults, (spark plugs, plug wires, distributor cap, rotor or ignition coil). It can also be caused by a problem with the fuel delivery system, (fuel pump, fuel pressure regulator, or leaking lines in the plenum). A fuel leak in the plenum may or may not set a DTC depending on how bad the leak is. Check fuel pressure and leakdown rate and post your results. Key on, engine off, pump running, pressure must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the pump shuts off.

kvn4

did you clean the egr vavle . surging problem on mine ,cleaned[ full of carbon]works smooth , just a sugestion