2008 Yukon Denali vey rough misfire out of nowhere

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Drew1987gn

TYF Newbie
Joined
Oct 19, 2024
Posts
3
Reaction score
0
Hi to all. New to this forum and looking for some guidance. I have a 2008 Yukon Denali. Running fine then within a minute while drivIng it went from a little rough to an extremely bad misfire. Really popping through the exhaust. I had to pull into a parking lot and shut her off. Barely made it into the parking lot! The check engine light did not come on which is throwing me off as to where to start troubleshooting. I would think the check engine light would have came on if it was a bad coil, clogged cat, maf but nothing. Any ideas? Should I put my scanner on it anyway? It would be greatly appreciated. Thank you!
 

wjburken

Supporting Member
Joined
Dec 26, 2017
Posts
9,923
Reaction score
27,403
Location
Eastern Iowa
Your 2008 shouldn’t have AFM so it shouldn’t be a collapsed lifter.

I have had that happen exactly twice in our Yukon Denali’s. Both times, it was a broken valve spring. It takes about 45 minutes to pull your valve covers to see if you have a broken valve spring.

Just had to replace one on our 2013. Also had to do it on our 2007 when we had it.
 

Joseph Garcia

Supporting Member
Joined
Aug 2, 2018
Posts
7,294
Reaction score
9,833
Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.
 
OP
OP
D

Drew1987gn

TYF Newbie
Joined
Oct 19, 2024
Posts
3
Reaction score
0
Good morning! Even though my Yukon was misfiring and no check engine light on, I did drive home the next morning (about 2 miles). When I got home and backing up, the check engine light finally came on and was blinking. I shut her off and put my scanner on. 3 codes showed up. P0300 (misfire), P0151 (O2 sensor bank 2, sensor 1) and P0174 (Too lean bank 2). I'm thinking a bad injector. I'm going to start troubleshooting there. See if the connections are good. I'll check the fuel pressure. Pull the plugs and take a look at them to see if the plugs to tell me which cylinder is misfiring. I use regular 85 octane.
 

B-train

Full Access Member
Joined
Sep 12, 2022
Posts
2,232
Reaction score
3,843
85 octane is also an issue. These motors can run fine on 87, but definitely like premium or better due to the compression ratio.

If you have E85 available, you can make a blend of 25 to 30 percent of total capacity (I go by the fuel used counter on the DIC), and that will give you 93-97 octane. My 2008 Denali LOVES that blend. I get the same, or better, than 87 fuel mpg. It's less than premium non-ethanol, but the cost per mile is WAY less, so I don't really base it off mpg anymore. I just use the mpg to see where I'm at per tank of fuel.
 
Last edited:

mikez71

Full Access Member
Joined
Mar 9, 2023
Posts
1,352
Reaction score
1,574
Sounds like you need that bank 2 sensor 1. That might he enough to cause all those codes.?

I would replace that sensor first before getting into pulling plugs and fuel injectors.

If it was just 1 cylinder misfiring, you would have probably gotten a cylinder specific code I think...
 
Last edited:
OP
OP
D

Drew1987gn

TYF Newbie
Joined
Oct 19, 2024
Posts
3
Reaction score
0
My thought was that if I was having a misfire, it would cause the O2 sensor to be off. I do agree with you that it would be an easy step just to replace the O2 sensor and see what happens.
 

Fless

Staff member
Super Moderator
Joined
Apr 2, 2017
Posts
11,737
Reaction score
23,853
Location
Elev 5,280
Before you do any work on it, know how much ethanol is in your fuel and compare that to what a scanner reads for alcohol content. If they don't match within a few percentage points, you may want to consider resetting the alcohol content (unless you're actually running E85).
 

Forum statistics

Threads
132,082
Posts
1,862,044
Members
96,543
Latest member
nicbop03
Top