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Pete
Pete, Auto Mechanic
Category: Chevy
Satisfied Customers: 16150
Experience:  14 years GM dealer Technician.
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i have a 2002 chevy blazer 4.3 ..code po300 ..what could be the issue

Resolved Question:

i have a 2002 chevy blazer 4.3 ..code po300 ..what could be the issue
Submitted: 2 years ago.
Category: Chevy
Expert:  Pete replied 2 years ago.
Hello,I will be glad to try and assist you with this,Welcome to Just Answer.

Hi.

One common issue is a stuck fuel injector or an injector that isn't spraying/atomizing properly,in allot of cases cleaning the injector wont correct this fault and thew injector has to be replaced.

This would have to be tested using a fuel pressure test gage and a scan tool to pulse each injector to see if the injector drop on all cylinders is within 1.5 psi of each other,any that are outside of this range need replaced since cleaning didn't correct them.

This can also be caused by low compression on one or more cylinders,a compression test needs done on all cylinders,they should all be right around the same compression,if you have one or more that are 15 to 20 pounds different in compression then compression is at fault and the most likely cause is valve issues in the cylinder head.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Customer: replied 2 years ago.

if the vehicle had such issues that you may be implying the engine would run bad...again smooth idle...lots of power...

Expert:  Pete replied 2 years ago.
O.k.

With a smooth idle and no running issues this may be due to the crankshaft learn as in some cases using a scan tool to relearn the crankshaft position can correct this type of fault here.

If this doesn't correct it GM has come out with a bulletin on the 4.3 liter engines to shim the crank sensor on the timing cover for this type of fault here.You can obtain this shim kit from a dealer,install one shim at a time,relearn the crankshaft sensor position with a scan tool and see if the fault is corrected.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Customer: replied 2 years ago.
how bout the simplest 1st...a battery issue, gas cap? 1 thing that happens when i start it cold is the lights flicker..inside, dash dome etc....could anything electrical be the issue...i have o2 sensors coming soon..i heard that was possible cause..im just so dizzy with this issue..i want to sell it but i cant with that light flashing...
Expert:  Pete replied 2 years ago.
With lights flickering this can be caused by low voltage from a failing/weak battery or failing alternator as these components can cause this here and need tested.Make sure your battery cables at the battery are clean and tight as well as this will cause these faults.

The electronic ignition switch is also common to fail internally and cause voltage issues but I haven't seen it cause misfire codes but it is possible if the voltage being supplied to ignition fuses is low from this switch.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Pete, Auto Mechanic
Category: Chevy
Satisfied Customers: 16150
Experience: 14 years GM dealer Technician.
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