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P0300 5.3 Need some help

Brad Kermes

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Brad Kermes Enthusiast

Brad Kermes

Posted
Posted

I noticed there's a couple other p0300 threads on here right now however my symptoms are a little different than the other users....

 

2004 silverado 1500 5.3L 186,000 miles 5.13 gears front and rear.

My truck has an engine light on for the wonderful code P0300, random misfire. (Flashes occasionally)
Symptoms: Rough idle, poor acceleration, ticking, occasional stalling (Usually happens when steering wheel is being turned at idle.)
I have been throwing parts at it the past couple weeks and have made no progress. I put in a new fuel pump, new crank position sensor and I tested all coils/plugs to ensure there was spark.
I dropped the truck off to a shop to have them do some "live scanning" however they gave it back to me and said just change the plugs and wires. They have never been replaced on this vehicle however I feel like my issue is somewhere else since my spark test was okay. Opinions?
Long story short, I really need some help because I am unsure which direction to head next. Could my intake manifold gasket be bad? Truck has had a small coolant leak for some time now....
Any help is appreciated because I’m 4 months passed inspection and if i can’t fix this I’m selling it.
Im borrowing a friend’s harbor freight cen-tech scanner to see if i can do some live data reading myself. Maybe its a bad o2 sensor or something.
Thanks,
Brad
ChevroletTough Enthusiast

ChevroletTough

Posted
Posted

I'd replace the plugs and wires, that's easy. I did that too chasing this (ended up being the crank shaft position sensor). I also had the intake checked for leaks. Sounds like you have 2 things right there that need to be addresses. That's high mileage on a single set of plugs and wires (if that is indeed the case). I've fired through 2 sets and I'm @ 120,xxx

anumber1 Enthusiast

anumber1

Posted
Posted

At that mileage and age, suspect the O2 sensors, Maf sensor, and associated wiring as well as the plug wires and spark plugs.

 

If you have not replaced the plugs, use original equipment. Anything but will be trouble eventually. If the truck has aftermarket plugs in it, put the original AC Delco plugs back in it.

 

Clean the throttle body,

Brad Kermes Enthusiast

Brad Kermes

Posted
  • Author
Posted

Thanks for the replies guys, I just picked up some plugs and wires, truck had bosch platinums it in and have lasted a while so I'm gonna put those back in it. A few people told me to check my fuel rail/injects as well because they could be clogged up. Gonna do some work to it this weekend.

Brad Kermes Enthusiast

Brad Kermes

Posted
  • Author
Posted

At that mileage and age, suspect the O2 sensors, Maf sensor, and associated wiring as well as the plug wires and spark plugs.

 

Ill check the 02 sensors as well but don't those usually throw a separate engine code, or am I mistaken?

Thx

anumber1 Enthusiast

anumber1

Posted
Posted

O2 sensors will throw a code of their own if they are really bad but many times they can be marginal and not throw a code but still cause problems.

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