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cylinder 7 miss fire

how do I identify cylinder 7?

cylinder 7 miss fire

Postby kjfalk1 [OP] » May 22 2020, 2:17pm

I have a cylinder 7 miss fire, how do identify it and what could be the reason other than bad plug?
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Re: cylinder 7 miss fire

Postby ricka182 » May 22 2020, 2:26pm

Welcome to the forum. The cylinders are numbered from front to back...so looking at engine from front of truck, it would go #1 front right, #2 front left, etc... #7 would be on the driver side, closet to the cab...nice and east to get to.. not as bad as #8, which is a real bear, but it's not that bad to get to #7.

I would check the plug, the wire, and the coil. You could replace all 3, or one at a time if you wanted to try to toss parts to fix the issue. IMO, I would replace all plugs, and wires...if it doesn't go away, it could be the coil(s). If you replaced all 3, on each cylinder and still had the issue, you have a more serious problem.

But at the least, check the plug at #7... You can post a pic here and we can see if there are any telltale signs of what is causing the issue. But just a bad plug alone could do it, and if you don't know when it was last replaced, it's fairly simple and not a lot of money to replace plugs and wires for all of them.
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Re: cylinder 7 miss fire

Postby kjfalk1 [OP] » May 22 2020, 2:40pm

I had all plugs replaced about 35000 miles ago by the dealer
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Re: cylinder 7 miss fire

Postby ricka182 » May 22 2020, 3:05pm

Then I would just check the #7 plug then. Shouldn't be too difficult, but you'll the right adapter on your socket to get it out. You also want to pull the wire with the right tool to avoid damaging it. Neither are a lot of money, and good to have if you ever plan to do your own work. If you just yank on the wire, you could damage the internals, and you'd have to replace it anyway and possibly the plug as well.

Once you have the plug out, if there is a lot of damage or carbon, etc...maybe check another plug. if only #7 is bad, you have a different issue that you may want a dealer to diagnose.
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Re: cylinder 7 miss fire

Postby kjfalk1 [OP] » May 22 2020, 4:18pm

Thank you, I really appreciate the help
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Re: cylinder 7 miss fire

Postby tsuintx » May 22 2020, 4:47pm

Try those suggested above and see what happens. One thing to keep in mind is, however, that cylinder #7 is one of the ones that has the AFM crap that fails. But hopefully that's not your issue.
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Re: cylinder 7 miss fire

Postby nealinator » May 22 2020, 5:10pm

I would only be worried about that^ if there was any ticking noises. If so... not good.
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Re: cylinder 7 miss fire

Postby kjfalk1 [OP] » May 22 2020, 8:05pm

I just got back from my mechanic. So he changed the plug and coil of number 7 with number 3 and the problem stayed with number 7, so I was beginning to get worried that this is gonna turn into a costly repair. But then he checked the oil level in the motor and it was 2.5 quarts low, so he leveled it off and the problem went away. He drove for about 2 hours and I drove for a while and she runs straight as an arrow. It sure made me happy :D :D :D
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Re: cylinder 7 miss fire

Postby tsuintx » May 22 2020, 8:24pm

2.5 quarts??? When was it full last time? Adding 2.5 quarts of oil gets rid of cylinder misfire? Interesting, but good for you. Keep on trucking, then.

All GM products consume oil, but just so you know, excessive oil consumption is also one early sign of failing AFM lifters. And yes, as Neal said, they will eventually start to make noise, or just fail out of the blue, but a lot of time the other stuff (misfire in #7, oil consumption etc.) do happen first. So, if yours don't make noise, great. It's just good to be aware and know to keep an eye on things.
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Re: cylinder 7 miss fire

Postby kjfalk1 [OP] » May 23 2020, 1:01am

What kind of noise?
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