Bad engine? Code P0300 random multiple misfire?

THESOUNDGUY

MEMBER
2002 CHEVROLET ASTRO
4.3L
V6
2WD
AUTOMATIC
256,000 MILES

New cap, rotor, wires, plugs, cam sensor, crank sensor, mass air flow, octane booster, sea foam, air filter and still a bad miss. Code P0300 random multiple misfires. Thanks in advance for your help.

Friday, August 12th, 2022 AT 5:32 PM

5 Replies

KEN L

MASTER CERTIFIED MECHANIC
42,833 POSTS

We should start with a compression test, or you can send me a video of the engine cranking over so I can tell if the engine is in good shape or not.

This guide can help:

https://www.2carpros.com/articles/how-to-test-engine-compression

If the compression is good and the engine has fresh spark plugs etc., I would do a fuel filter because they can clog up limiting the amount of fuel getting to the engine.

Here is a video of the job being done and instructions in the images below for your car:

https://youtu.be/cMa2bp4jbNU

Clear the codes after the job is done. Check out the diagrams (below). Please let us know what happens.

Images (Click to make bigger)

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Saturday, August 13th, 2022 AT 9:40 AM

THESOUNDGUY

MEMBER
4 POSTS

So sorry sir, but I put a new fuel filter on it too, I just failed to put it in the list.

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Saturday, August 13th, 2022 AT 9:46 AM

KEN L

MASTER CERTIFIED MECHANIC
42,833 POSTS

It sounds like the fuel pump is starting to go out. To be sure this guide can help you check the fuel pressure. I have also included how to change the pump out just in case in the images below.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Key On Engine Off .................... 55-62 psi

Check out the diagrams (below). Please let us know what happens.

Images (Click to make bigger)