P0307 2014 Suburban

[MN-cj]

On way to work at stop sign and stop light, I noticed the tachometer "bobble" a little at idle. It has had ever so so slight done that since I got it in 2014 and stealership said it was normal. It was a little more than that this time I thought but it went away and no light came on. After work, I remote started it and it was not running when I came out. Started it & the check engine light came on blinking and it had turned off the stability track and traction control plus running like it was missing. I put my OBDII reader in and pulled up TorquePro to see the code which it stated cylinder 7 misfire (P0307). Truck has 227k miles on it.

1. Assuming I need to replace plug wires and plugs? (OEM original I hate to say)
2. Also assuming from research ACDelco 748UU and ACDelco 41-110 plugs are way to go?
3. Assuming I don't need to replace the coils, correct?

Thanks in advance for the advice.

 

[Marky Dissod]

... 227k miles on it.

1. Assuming I need to replace plug wires and plugs? (OEM original I hate to say)
2. Also assuming from research ACDelco 748UU and ACDelco 41-110 plugs are way to go?
3. Assuming I don't need to replace the coils, correct?

1. Ten years, 227k miles, original plugs and wires ... YES ... time to change them, finally.
2. If those are compatible with what's called for, should be fine (unless you want to upgrade for some reason ...).
3. Being a pessimist, I'd relocate the 7th coil to a different cylinder. If the misfire follows that coil, replace that coil sooner.
Then buy at least seven more coils now (while they're cheaper) to replace later.

 

[MN-cj]

Thanks Marky. Moving 7 up to 1 or 3 would make it a little easier to get to and verify if it is the problem. Are you suggesting the price of coils are going to go up?

Looking on AutoZone just now, I assume figure out if I have the square or round coil and then buy ACDelco D510C or D514A respectively?

 

[Marky Dissod]

Are you suggesting the price of coils are going to go up?

Has anyone ever suggested the price of anything going DOWN?
I'd actually suggest that you buy whichever coil the hotrodders prefer.
They usually know which ignition components live with enthusiasm better, if there is such a thing.

 

[Fless]

Isn't cylinder #7 an AFM cylinder?

 

[Marky Dissod]

Cylinders 1, 4, 6, & 7 are the lazier ones, yes.

 

[wjburken]

I would simply begin with changing plugs and wires. If that doesn’t take care of it, then swap coils.

#7 seems to takes the brunt of any oil that gets sucked into the intake from the PCV hose from the DS valve cover so tends to foul sooner than the others.

 

[Marky Dissod]

#7 seems to takes the brunt of any oil that gets sucked into the intake from the PCV hose from the DS valve cover, so #7 tends to foul sooner than the others.

Besides disabling / deactivating V4 mode is there anything ELSE that can be done to make #7 less likely to suck?

 

[Fless]

Besides disabling / deactivating V4 mode is there anything ELSE that can be done to make #7 less likely to suck?

Updated driver's side valve cover. Catch can.

 

[wjburken]

Besides disabling / deactivating V4 mode is there anything ELSE that can be done to make #7 less likely to suck?

Put a catch can in.

#7 is an issue independent of AFM.

Since this is on a 2014, I’m assuming it already has the newer valve cover design from the factory that is supposed to reduce the amount of oil that’s sucked into the intake.

 

[MN-cj]

So just to report back, I changed out all 8 plugs with ACDelco 41-110 and ACDelco 748UU wires from AutoZone. As suggested, I also swapped coil #7 and #3 in case the miss returned I would know if it was the coil or if it was something else. Even though the plugs had 10 years on them, I think taking the 2nd battery tray off to get to the coil bolt I dropped thru the hole in it accidently when I was swapping coils took longer than doing the entire driver's side plug and wire change. Passenger side obviously took longer but removing the airfilter and it's entire housing helped open up the area to reach in from the front to get your arm in there while standing on a milk crate.

One thing I noticed is right below the threaded stud to the left of coil #8 towards the firewall, there was a slight drip of antifreeze. I noticed it because a drip hit my hand while trying to get #8 out. it must not be hitting the header or I would smell it burning. Not really seeing any large loss quickly in antifreeze either (knock on wood). Any idea what is in that area which could be dripping?

 

[wjburken]

One thing I noticed is right below the threaded stud to the left of coil #8 towards the firewall, there was a slight drip of antifreeze. I noticed it because a drip hit my hand while trying to get #8 out. it must not be hitting the header or I would smell it burning. Not really seeing any large loss quickly in antifreeze either (knock on wood). Any idea what is in that area which could be dripping?

What is in the area by #8? You have two heater hoses going into your heater core by #8. I am assuming you also have rear heat so there are two plastic tees that have a tendency to fail. I would very carefully check that area over and plan on replacing the tees and possibly the hoses particularly if they are original at 227K, you are on borrowed time.

 

[Fless]

What is in the area by #8? You have two heater hoses going into your heater core by #8. I am assuming you also have rear heat so there are two plastic tees that have a tendency to fail. I would very carefully check that area over and plan on replacing the tees and possibly the hoses particularly if they are original at 227K, you are on borrowed time.

^^ x2 ^^

 

[Marky Dissod]

... two heater hoses going into your heater core by #8 ... there are two plastic tees that have a tendency to fail.
I'd very carefully check that area over and plan on replacing the tees and possibly the hoses particularly if they are original at 227K.
You are on borrowed time.

One of my favorite things about this Z71:
when the road gets really bumpy and everyone else slows down, I can even speed up a bit.
Except, one time, the road abruptly switched from 'paved' to 'under construction'.
It was bumpy enough to break either the 'Y' or the 'T' (don't remember which).

Could not afford the
permanent solution
but I will buy them later this year.
$200 is a small price to never have to ever replace them again.

 

[donjetman]

So just to report back, I changed out all 8 plugs with ACDelco 41-110 and ACDelco 748UU wires from AutoZone. As suggested, I also swapped coil #7 and #3 in case the miss returned I would know if it was the coil or if it was something else. Even though the plugs had 10 years on them, I think taking the 2nd battery tray off to get to the coil bolt I dropped thru the hole in it accidently when I was swapping coils took longer than doing the entire driver's side plug and wire change. Passenger side obviously took longer but removing the airfilter and it's entire housing helped open up the area to reach in from the front to get your arm in there while standing on a milk crate.

One thing I noticed is right below the threaded stud to the left of coil #8 towards the firewall, there was a slight drip of antifreeze. I noticed it because a drip hit my hand while trying to get #8 out. it must not be hitting the header or I would smell it burning. Not really seeing any large loss quickly in antifreeze either (knock on wood). Any idea what is in that area which could be dripping?

I heard that the AC Delco spark plug # 41-110 has been superseded by # 41-162 for Gen4 LS engines.

 

[MN-cj]

Sounds like good advice. Without going out to look in the dark, are you talking about the molded Branched Heater Hose like the two links below? They have a tee molded into them.

GATES 22554 https://www.rockauto.com/en/moreinf...pcZafsPGIG/An8tacofS/xV3LhsDS36YVj2NGN***9A==
or
GM GENUINE 15834773 https://www.rockauto.com/en/moreinf...pcZafsPGIG/An8tacofS/xV3LhsDS36YVj2NGN***9A==

 

[MN-cj]

I heard that the AC Delco spark plug # 41-110 has been superseded by # 41-162

The 41-110 plug was the original ones I just removed from my truck and from searching around the forums, the story seems to be these were made by Denso for ACDelco. The part number change to 41-162 plugs were when NGK started making them for ACDelco. So I would not need to find it in the future, I wrote down for reference in my truck stuff:
ACDelco 41-110 or GM# 12621255 (Denso made) changing to 41-162 (NGK made).
The first set went 10 years and 227k miles so hopefully the 2nd set are good enough to go a few years until next replacement.