09 Yukon Cyl 5 Misfire - SOLVED

[Robochop]

Hello everyone, I am having a similar issue (09 Yukon SLT 5.3 engine). I am getting a missfire in (Cyl #5) when I step on the gas, the check engine light comes on and flashes and so does the stabil-trak and traction control dash light and it also triggers the alarm bells through the speakers. I bought it used with 105k miles and it now has 142k. This problem popped up all of a sudden like with no warning. I changed spark plugs about 3000 miles ago as I figured it was time. I have heard stories about this motor having cam shaft issues. I did pull the # 5 spark plug and swapped it with the #1. They both looked the same, a little wet with some brown coloring. Today I did a compression test and all cylinders have 175 psi. I am attaching a pic of the plugs and all on bank 1 (driver side) look wet, while the other side looks good? I can't imagine all 4 coils being bad? I turned off the light with my OBD2 reader, but the codes immediately returned after a short drive. Any suggestions? Thanks

 

[Geotrash]

Hello everyone, I am having a similar issue (09 Yukon SLT 5.3 engine). I am getting a missfire in (Cyl #5) when I step on the gas, the check engine light comes on and flashes and so does the stabil-trak and traction control dash light and it also triggers the alarm bells through the speakers. I bought it used with 105k miles and it now has 142k. This problem popped up all of a sudden like with no warning. I changed spark plugs about 3000 miles ago as I figured it was time. I have heard stories about this motor having cam shaft issues. I did pull the # 5 spark plug and swapped it with the #1. They both looked the same, a little wet with some brown coloring. Today I did a compression test and all cylinders have 175 psi. I am attaching a pic of the plugs and all on bank 1 (driver side) look wet, while the other side looks good? I can't imagine all 4 coils being bad? I turned off the light with my OBD2 reader, but the codes immediately returned after a short drive. Any suggestions? Thanks

Are there any knocking noises or other unusual sounds coming from the engine either at idle or under throttle? And are there any other codes being thrown besides the misfire code?

 

[Robochop]

Are there any knocking noises or other unusual sounds coming from the engine either at idle or under throttle? And are there any other codes being thrown besides the misfire code?

No noises at all! That's why I was happy with this vehicle as it didn't have the "GM tick". I was also going to change the plugs while I have them out. They are the 41-162Ac Delco plugs recommended on this site.

 

[Fless]

Your picture -- are those the new (3k mile), or the original plugs?

Those are way worn and if they're the ones you put it, they're probably counterfeit. Where did you buy them?

 

[Robochop]

Your picture -- are those the new (3k mile), or the original plugs?

Those are way worn and if they're the ones you put it, they're probably counterfeit. Where did you buy them?

LOL, I have been reading about this on the site. Of course I got them on Amazon, so I agree with the phony plugs! I going to get some from the local parts store and put them in. Thanks!

 

[Geotrash]

LOL, I have been reading about this on the site. Of course I got them on Amazon, so I agree with the phony plugs! I going to get some from the local parts store and put them in. Thanks!

I think you found your smoking gun.

 

[Robochop]

Yup, put them in and it runs great! I cleared all the codes and none have come back yet. I would have never thought about counterfeit plugs, especially since they were AC Delco. I gotta wonder what else is out there that is no good!?!
Thanks to everyone who chimed in!

 

[Dustin Jackson]

@Robochop I would avoid anything AC Delco or GM Genuine from Amazon

 

[petethepug]

Can you find the seller on Amazon you got the plugs from? There’s a Genuine GM shop on there and need to know if it was them. Nice work updating the status to “solved”

 

[Fless]

Nice work updating the status to “solved”

You're welcome.