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camarochris, Chevy Mechanic
Category: Chevy
Satisfied Customers: 87
Experience:  10 years personal experience with GM, Specifically Chevy's
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99 Tahoe-OBDII code PO305-engine cylinder 5 misfire

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That means that the number 5 cylinder isn't firing all the time you might notice it when you are accelerating or going uphill. To fix this problem check the distributor coil, cap, wires and spark plugs. Then go to your nearest parts store and ask them to clear your vehicles trouble codes.
Customer: replied 8 years ago.
What I notice is a slight pinging when I accelerate. The service engine light comes on and goes out sporadically.
sound like your are getting a spark knock not a misfire. Try and run some premium fuel in it or a good fuel injector cleaner/octane booster and see if that helps. The computer might be confusing the spark knock for a misfire. If it goes away with the change in fuel you might want to consider switching to a different gas station to get your fuel. Some places like wal-mart gas stations do not use a good quality gas and can cause the spark knock.
Customer: replied 8 years ago.
I just started using Red Line fuel system cleaner which was recommended by another JustAnswer expert. The vehicle I'm using it in was just purchased used so I'm going through it to fix whatever I find. Would it be feasible to first replace the spark plug (I intend to change them all anyway because I'm told they get fouled around 75K miles-have 67K on vehicle) in the #5 cylinder and if it stops after clearing the code I found my culprit. If not, change the spark plug wire, if not then comes the distributor cap and wires. It's cold out and have to work outside, so Ill be waiting for a not so cold day to finish the tune-up.
That would be a good place to start. The number 5 cylinder is the third one from the front on the drivers side. Please keep me updated.
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