2013 GMC Yukon XL 5.3 - AFM Issues Early Indicator?

[GuestTahoe24]

Hi All!
During a pre-purchase test drive of a 2013 GMC Yukon XL 5.3 with 110k, I noticed a very prominent misfire while in drive. Mentioned to the salesperson that prior to moving forward, this issues would need to be looked at/addressed (Cadillac Dealership).

Next day, the dealer says the Tech could not find an issue, since there were no codes present (CEL not illuminated) however-since he could feel the misfire- they'd go ahead and replace the spark plugs due to mileage (110K). After the spark plug replacement, the misfire was still present and apparently the tech was able to identify cylinder #6 as the issue so they replaced the coil pack. Misfire was still present (#6 cylinder). The salesperson says the Tech "got help from the big engine Tech" who advised him to pull the spark plug back out for cylinder 6 and found the "plug was smashed before it was installed" (SN: it takes quite a bit to bend the ground strap on a plug, doesn't happen without noticing!). "Come on back for another test drive"

Just returned from test drive #2. Not only was the misfire still present in drive, it was worse and now present idling in park as well. During the test drive, I stopped and checked the spark plug wire connections. I found the wires on #6 and #3 were not completely clicked onto the coils. After securing these, the misfire/stumble was less prominent in idle but certainly still present in drive. Dealership doesn't want to go further as they're saying it's normal (definitely isn't) and is not budging on the price.

Also noticed a wide range in the oil pressure. In gear and at a stop, the oil pressure gauge was pretty steady halfway between 20 and 40 PSI but would increase to nearly 50 PSI upon acceleration (this is an approximation of course, based on the reference gauge). Normal for these platforms?

What are your thoughts on this? Are these early indications of a worn cam from AFM issues? I should note, the engine had NO ticking or odd noises.

TL/DR: Engine misfire/constant stumble in gear. Wide oil pressure range. No check engine light. AFM cam failure indicator?

 

[swathdiver]

Without being able to put a scan tool on it, walk away unless you are prepared to overhaul the top of the engine. Oil pressure seems fine as you describe it.

Motor probably has a partially collapsed lifter or bad intake gaskets.

 

[iamdub]

Hi All!
During a pre-purchase test drive of a 2013 GMC Yukon XL 5.3 with 110k, I noticed a very prominent misfire while in drive. Mentioned to the salesperson that prior to moving forward, this issues would need to be looked at/addressed (Cadillac Dealership).

Next day, the dealer says the Tech could not find an issue, since there were no codes present (CEL not illuminated) however-since he could feel the misfire- they'd go ahead and replace the spark plugs due to mileage (110K). After the spark plug replacement, the misfire was still present and apparently the tech was able to identify cylinder #6 as the issue so they replaced the coil pack. Misfire was still present (#6 cylinder). The salesperson says the Tech "got help from the big engine Tech" who advised him to pull the spark plug back out for cylinder 6 and found the "plug was smashed before it was installed" (SN: it takes quite a bit to bend the ground strap on a plug, doesn't happen without noticing!). "Come on back for another test drive"

Just returned from test drive #2. Not only was the misfire still present in drive, it was worse and now present idling in park as well. During the test drive, I stopped and checked the spark plug wire connections. I found the wires on #6 and #3 were not completely clicked onto the coils. After securing these, the misfire/stumble was less prominent in idle but certainly still present in drive. Dealership doesn't want to go further as they're saying it's normal (definitely isn't) and is not budging on the price.

Also noticed a wide range in the oil pressure. In gear and at a stop, the oil pressure gauge was pretty steady halfway between 20 and 40 PSI but would increase to nearly 50 PSI upon acceleration (this is an approximation of course, based on the reference gauge). Normal for these platforms?

What are your thoughts on this? Are these early indications of a worn cam from AFM issues? I should note, the engine had NO ticking or odd noises.

TL/DR: Engine misfire/constant stumble in gear. Wide oil pressure range. No check engine light. AFM cam failure indicator?

A 2013 is gonna have the latest and greatest versions of the AFM components available for this platform. 110K miles is considerably low for AFM issues, or any serious issues, for that matter. That's not to say that an AFM failure (present or impending) isn't a possibility. It could be something stupid simple or a major repair. It needs proper diagnostics by a knowledgeable tech, and a third party in this case. The dealership, and a Cadillac one at that, crossing their fingers and throwing parts at it doesn't garner any confidence from me. This platform has been around plenty long enough that there aren't any real mysteries and a solid diagnosis shouldn't take very long. If the dealership has it at a "no engine issues" price and isn't gonna budge appropriately, it's safest to walk away. If it sits long enough and enough people check it over and pass on it, they'll be forced to properly diagnose it and either repair it or drop the price and sell it as-is or offload it at an auction.

 

[BlaineBug]

I wouldn't buy it with an issue that they are not willing or capable of diagnosing.

 

[wjburken]

You are the one with the power here. It’s okay to walk away if you’re not happy or comfortable.

 

[Doubeleive]

Hi All!
During a pre-purchase test drive of a 2013 GMC Yukon XL 5.3 with 110k, I noticed a very prominent misfire while in drive. Mentioned to the salesperson that prior to moving forward, this issues would need to be looked at/addressed (Cadillac Dealership).

Next day, the dealer says the Tech could not find an issue, since there were no codes present (CEL not illuminated) however-since he could feel the misfire- they'd go ahead and replace the spark plugs due to mileage (110K). After the spark plug replacement, the misfire was still present and apparently the tech was able to identify cylinder #6 as the issue so they replaced the coil pack. Misfire was still present (#6 cylinder). The salesperson says the Tech "got help from the big engine Tech" who advised him to pull the spark plug back out for cylinder 6 and found the "plug was smashed before it was installed" (SN: it takes quite a bit to bend the ground strap on a plug, doesn't happen without noticing!). "Come on back for another test drive"

Just returned from test drive #2. Not only was the misfire still present in drive, it was worse and now present idling in park as well. During the test drive, I stopped and checked the spark plug wire connections. I found the wires on #6 and #3 were not completely clicked onto the coils. After securing these, the misfire/stumble was less prominent in idle but certainly still present in drive. Dealership doesn't want to go further as they're saying it's normal (definitely isn't) and is not budging on the price.

Also noticed a wide range in the oil pressure. In gear and at a stop, the oil pressure gauge was pretty steady halfway between 20 and 40 PSI but would increase to nearly 50 PSI upon acceleration (this is an approximation of course, based on the reference gauge). Normal for these platforms?

What are your thoughts on this? Are these early indications of a worn cam from AFM issues? I should note, the engine had NO ticking or odd noises.

TL/DR: Engine misfire/constant stumble in gear. Wide oil pressure range. No check engine light. AFM cam failure indicator?

rather hard to believe..... particularly from a cadillac dealer
keep shopping I guess...... not like there isn't a ton of these around
prices have fell thru the floor.
OR if you really like it, buy a powertrain warranty or make sure they provide one in writting.
then just keep taking it back until it gets resolved.
depending on the type of warranty it could be taken to any gm dealer or shop willing to work with the warranty provider.
keep in mind that even with a warranty any "diagnostic" cost's not resulting in finding a verifiable issue will come out of your pocket.

otherwise there is no way to "guess" if it is this, that or the other causing the issue, requires a deeper diagnostic.

 

[petethepug]

I’ve noticed the Cadillac dealerships seem to have both the best and worst of GM’s attributes. Smells like AFM. Sounds like a self destructive hardball staff that eats its own.

If your spidey senses are tingling, then you’ve still got game. Those guys are asking you to reach inside a bear trap to grab the keys. Even if they gave you a service contract, they’d F with the Contract Admin to sabotage the repair with inflated part prices.

If it’s a good deal and you’re set on that truck, just make sure you CYA and get a S/C that has a low or $0 deductible so you can have it serviced somewhere else. Every one of the posts on here is spot on.

All the Best! M