P0300 1996 K1500

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Sterek

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I just bought a truck with a random cylinder misfire. Little back story on the truck, it was this guys brothers who passed away, he parked the truck and it sat for over a year. I went to look at it wouldn't start, i noticed a spark noise which i then saw coming off the distributer was chewed through by a rat. He grabbed one from another truck and it started right up. Truck was misfiring badly, which it threw the could p0300. Could the gas that is in it atm be bad we put a gallon of fresh gas in but still running rough. Thanks for reading and feel free to ask any questions.
 

RawbDidIt

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I just bought a truck with a random cylinder misfire. Little back story on the truck, it was this guys brothers who passed away, he parked the truck and it sat for over a year. I went to look at it wouldn't start, i noticed a spark noise which i then saw coming off the distributer was chewed through by a rat. He grabbed one from another truck and it started right up. Truck was misfiring badly, which it threw the could p0300. Could the gas that is in it atm be bad we put a gallon of fresh gas in but still running rough. Thanks for reading and feel free to ask any questions.
Sitting for a year? Yeah, the gas is probably bad. There could be other issues too, but I'd start with siphoning out the old and putting in fresh gas. If the problem persists, run a scanner and visually inspect all wires and lines.

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dirtautoguy

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I agree with raw. I had a snowmobile that acted similar. I kept getting oil/water milkshake at the cylinders (2stroke oil injection) then eventually it wouldn’t run at all. I finally dipped a stick in the tank and went a long ways away from anything flammable and found that the gas on the stick wouldn’t even start to light. Draining the tank and fresh gas it ran perfect. It’s a little different vehicle but same concept and a simple place to start.

Also, I had a similar issue on my 96 K1500. It had some bad misfires that cleared up after a good time up but I still got a po300 code fairly often. It also would crack distributor caps about every 3 months. I finally replaced the whole distributor shaft and haven’t had any issues since. I’m not sure what was wrong with it but it was the last thing I hadn’t replaced.
 

Sterek

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Sitting for a year? Yeah, the gas is probably bad. There could be other issues too, but I'd start with siphoning out the old and putting in fresh gas. If the problem persists, run a scanner and visually inspect all wires and lines.

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okay i will attempt to get some fresh gas in it later and update you guys.
 

Sterek

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Make sure you Siphon out the old first. It's not doing you any favors.

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well the truck has very low fuel like on empty so i i couldn't siphon anything out. im gonna grab gas from the station and add some enzyme furl treatment.
 

RawbDidIt

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well the truck has very low fuel like on empty so i i couldn't siphon anything out. im gonna grab gas from the station and add some enzyme furl treatment.
Ok, that little bit mixed with a full tank of fresh grass should be ok. Let her pump the fresh fuel in on her own, the seals and moving parts above the oil pan are going to be dry until she runs for a minute or two, so be patient and don't spin a bearing before she gets a chance to get oil to it. I'm a fan of seafoam, but that's a personal preference, anything you can add to stabilize the new fuel and blow out the cobwebs should be ok.

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Schurkey

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Do you REALLY have a P0300 code, or you you have a cheap code reader that's providing GENERIC codes instead of the proper, specific code?

The REAL code might be P0302, or P0305, or whatever cylinder is actually misfiring.

Gasoline a year old wouldn't bother me a bit. I fill all my portable gas tanks in the fall, so I have fuel to run a generator in the winter if I have to. I spend the rest of the year using up that fuel in my TBI pickup, riding lawn mower, and other garden equipment.
 

Sterek

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put 5 gallons in and cleared codes. Started it up and it was rough, set same code right after. I have a AutoLink scanner sure it isn't the most sufficient compared to snap on but im pretty sure it would be able to see if just one cylinder was acting up
 

Schurkey

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Amazon has an Autel AutoLink code-reader for $35. No, it's not going to give you specific codes. You'll get generic codes at that price level. The description even says it doesn't provide "enhanced" codes.

https://www.amazon.com/Autel-AutoLink-AL319-Scanner-Automotive/dp/B007XE8C74

'Course, I've been wrong before, and I've never used an Autel code-reader.

Pull the plugs, look for obvious problems, test the plug wires--maybe you have an open wire, or one that's grounding. Test the cranking compression of each cylinder. This could be fuel-related, but ignition and compression are easier to test.
 
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