Engine mis-firing again

[lspann3525]

For the last week I have been getting a P0300 / P1153. With my obd scanner hooked up I was getting misfires on cylinders 4 and 8. After swapping coils from Cylinder 6 to 8. And coil 8 to 6. The misfires disappeared on Cylinder 8. But im still getting a misfire on cylinder 4. I am going to try installing a new plug and swapping in a spare coil I have laying around or from a working cylinder.

I am also curious about the condition of the fuel pump because its never been changed and im getting close to 300k.. Does anyone know what i'll need to test the fuel pressure at the rail..or can I use my obd scanner?

 

[Foggy]

Put your info about the truck in your signature or least in your post.
We don't know year, engine, etc
Then you'll prob get some info

 

[OR VietVet]

Put your info about the truck in your signature or least in your post.
We don't know year, engine, etc
Then you'll prob get some info

Beat me to it.

 

[lspann3525]

2008 tahoe 5.3...sorry guys

 

[Foggy]

2008 tahoe 5.3...sorry guys

Cylinder 4 IS a dod/afm cylinder.. Prob time to pull off that valve
cover and see if the rockers are moving correctly .. could be a bad lifter(s)

 

[lspann3525]

Replaced spark plugs for cylinder 4 and 6 and no more misfires.

The AC Delco plugs I previously installed lasted almost 2 years.

Glad its not a lifter!

 

[lspann3525]

I did notice that cylinder 6 and 4 the plugs were cracked around the middle of the plug where the part number is located..What causes this?

 

[OR VietVet]

I did notice that cylinder 6 and 4 the plugs were cracked around the middle of the plug where the part number is located..What causes this?

Crack their is usually from poor install.

 

[LsHart]

But for the future, get u a noid light tester kit. U plug the corresponding noid light into the injector harness and the computer driver will make it blink. ( the light on the noid)noise. To test the harness and computer

 

[lspann3525]

Crack their is usually from poor install.

i dont see how you can poorly install a spark plug? it was gapped properly and not over or under torqued

 

[Charlie207]

i dont see how you can poorly install a spark plug? it was gapped properly and not over or under torqued

Could be a crib-death.

Luckily, plugs are cheap consumables.

 

[mikez71]

i dont see how you can poorly install a spark plug? it was gapped properly and not over or under torqued

There's some play in the plug socket, and there's usually a rubber donut inside to hold the plug.
This can apply sideways pressure to the plug end when LEANING on the socket while installing..
Pretty sure that's how I did one of mine in...

 

[OR VietVet]

i dont see how you can poorly install a spark plug? it was gapped properly and not over or under torqued

Like @mikez71 said, you can use a socket that does not have the rubber insert, like a spark plug socket would. You know, any old 5/8" deep socket will do. And even if you do use the correct socket, if you tighten by just pulling/pushing on the ratchet and not holding the socket completely straight on the plug, it can and does happen. But, if you think that my response is full of it, have a good day. I mean, I am new at this and never installed plugs before, but I did sleep at a Holiday Inn last night.