2017 Yukon hesitating/shuddering

[Td_symmons]

Hi all! New to the forum and first post:

I have a 2017 GMC Yukon 5.3 SLE 4WD (157k miles) with a hesitation issue. While accelerating, the vehicle experiences a slight shudder and acts like it has a very hard time accelerating until it downshifts and the shudder goes away. No trouble codes. Shudder/shake does not persist after letting off the gas pedal. No matter the speed (but it’s worse at highway speeds). The following maintenance was just completed about 1k miles ago to fix other issues- after which this new problem arose.

-New full set of OEM (nominal flow) injectors
-Intake port cleaning
-Tire rotate & balance
-Added some Lubegard platinum to the transmission fluid

Important info:
-Transmission rebuild at 130k miles
-Spark plugs replaced at 130k miles

This really acts like a low fuel pressure problem from experience diagnosing other vehicles, but I am not really sure.

I have attached an image of my most recent graph recording of some PIDs while this issue occurred. Note the circled area since the screenshot was taken while the problem was recreated.

Anybody else have this issue or know what to check for? I included the MAP sensor reading on the graph since I saw one person with this issue reported a faulty MAP sensor being the issue.

 

[Joseph Garcia]

@NickTransmissions , just to be sure that your issue in not related to your rebuilt transmission.

 

[Td_symmons]

Hi! I’m really not sure about it being the transmission. I went for a test drive monitoring torque converter slip and froze the data when I experienced it. Here’s some screenshots. Note the data values above the graph.

 

[NickTransmissions]

Hi all! New to the forum and first post:

I have a 2017 GMC Yukon 5.3 SLE 4WD (157k miles) with a hesitation issue. While accelerating, the vehicle experiences a slight shudder and acts like it has a very hard time accelerating until it downshifts and the shudder goes away. No trouble codes. Shudder/shake does not persist after letting off the gas pedal. No matter the speed (but it’s worse at highway speeds). The following maintenance was just completed about 1k miles ago to fix other issues- after which this new problem arose.

-New full set of OEM (nominal flow) injectors
-Intake port cleaning
-Tire rotate & balance
-Added some Lubegard platinum to the transmission fluid

Important info:
-Transmission rebuild at 130k miles
-Spark plugs replaced at 130k miles

This really acts like a low fuel pressure problem from experience diagnosing other vehicles, but I am not really sure.

I have attached an image of my most recent graph recording of some PIDs while this issue occurred. Note the circled area since the screenshot was taken while the problem was recreated.

Anybody else have this issue or know what to check for? I included the MAP sensor reading on the graph since I saw one person with this issue reported a faulty MAP sensor being the issue.

Those graphs show the TCC is behaving as expected, so whatever is causing your shudder/vibrations it's not the torque converter clutch and/or TCC electro-mechanical circuitry. If it was, your slip speed would be much higher than it's reading and the graphs would look completely different.

That said, it is interesting that the shudder goes away once you downshift.

- Is this pattern constant or intermittent?

- How does the vehicle feel power-wise when you take off from a stop?

- Have you checked your fuel pressure? If so what is it?

- Lastly, what transmission do you have? 6L80 or 8-speed (thinking you should have a 6L80 but will let you confirm/deny).

 

[Td_symmons]

Those graphs show the TCC is behaving as expected, so whatever is causing your shudder/vibrations it's not the torque converter clutch and/or TCC electro-mechanical circuitry. If it was, your slip speed would be much higher than it's reading and the graphs would look completely different.

That said, it is interesting that the shudder goes away once you downshift.

- Is this pattern constant or intermittent?

- How does the vehicle feel power-wise when you take off from a stop?

- Have you checked your fuel pressure? If so what is it?

- Lastly, what transmission do you have? 6L80 or 8-speed (thinking you should have a 6L80 but will let you confirm/deny).

Absolutely. It is very consistent. Any time I’m going about 70mph and press the gas pedal a bit harder, it will recreate the problem almost every time. Let go of the gas pedal, and it stops- and drives smoothly. It’ll also do it on cruise control under the same conditions.
When I take off from a stop, it feels just fine really. It’ll take off without a problem and speed up. I may have said “any speed” in my first post but it’s really only in highway speeds. I can’t really get it to happen much under 60mph. It’s quite noticeable though. After I did a full injector set replacement, I noticed the problem on my test drive. Went and got rotate and balance to make sure.
In my first post I included a pic monitoring fuel pressure. I’ll attach another one here, showing the freeze frame values at the top when the issue repeated. I have a 6L80. Thank you

 

[NickTransmissions]

Absolutely. It is very consistent. Any time I’m going about 70mph and press the gas pedal a bit harder, it will recreate the problem almost every time. Let go of the gas pedal, and it stops- and drives smoothly. It’ll also do it on cruise control under the same conditions.
When I take off from a stop, it feels just fine really. It’ll take off without a problem and speed up. I may have said “any speed” in my first post but it’s really only in highway speeds. I can’t really get it to happen much under 60mph. It’s quite noticeable though. After I did a full injector set replacement, I noticed the problem on my test drive. Went and got rotate and balance to make sure.
In my first post I included a pic monitoring fuel pressure. I’ll attach another one here, showing the freeze frame values at the top when the issue repeated. I have a 6L80. Thank you

Interesting...If you only started noticing the issue after you replaced the injectors, i'd be inclined to think one or more of the injectors are defective in some way that isn't showing up in the data or something got missed or damaged during the repair.

This also sounds like worn ring/pinion, specifically when the drive side of your ring and pinion gear set is excessively worn...My trans am was making a very high frequency vibration at high speeds, off throttle so the coast side of the ring/pinion were worn...But you would have noticed this long before you changed your injectors. Plus those rear axles/diffs rarely go bad in daily driver vehicles with only 150ish on the clock...It's worth checking for bad wheel bearings, u joints, etc as well, if you havent already.

Only other potential cause I can think of atm is either front or rear gear set in the trans is going out...They typically dont thow any codes; diagnosis is done by analyzing symptoms on test drive then looking for gear chunks, pieces in the pan.

All of the above assumes the the tire rotation and balance was done correctly and that there's no wheel or axle bearing or shaft problems

 

[Doubeleive]

Absolutely. It is very consistent. Any time I’m going about 70mph and press the gas pedal a bit harder, it will recreate the problem almost every time. Let go of the gas pedal, and it stops- and drives smoothly. It’ll also do it on cruise control under the same conditions.
When I take off from a stop, it feels just fine really. It’ll take off without a problem and speed up. I may have said “any speed” in my first post but it’s really only in highway speeds. I can’t really get it to happen much under 60mph. It’s quite noticeable though. After I did a full injector set replacement, I noticed the problem on my test drive. Went and got rotate and balance to make sure.
In my first post I included a pic monitoring fuel pressure. I’ll attach another one here, showing the freeze frame values at the top when the issue repeated. I have a 6L80. Thank you

post up what the MAF is showing when the problem occurs, fuel pressure appears to be within spec (at least what is being commanded anyway)

 

[Td_symmons]

Interesting...If you only started noticing the issue after you replaced the injectors, i'd be inclined to think one or more of the injectors are defective in some way that isn't showing up in the data or something got missed or damaged during the repair.

This also sounds like worn ring/pinion, specifically when the drive side of your ring and pinion gear set is excessively worn...My trans am was making a very high frequency vibration at high speeds, off throttle so the coast side of the ring/pinion were worn...But you would have noticed this long before you changed your injectors. Plus those rear axles/diffs rarely go bad in daily driver vehicles with only 150ish on the clock...It's worth checking for bad wheel bearings, u joints, etc as well, if you havent already.

Only other potential cause I can think of atm is either front or rear gear set in the trans is going out...They typically dont thow any codes; diagnosis is done by analyzing symptoms on test drive then looking for gear chunks, pieces in the pan.

All of the above assumes the the tire rotation and balance was done correctly and that there's no wheel or axle bearing or shaft problems

Great info. Thank you. I’ll check many of that this weekend.

 

[Td_symmons]

post up what the MAF is showing when the problem occurs, fuel pressure appears to be within spec (at least what is being commanded anyway)

Sure thing. Will do. I was under the impression that I was monitoring the fuel lift pump pressure output from a (low pressure/lift pump) fuel pressure sensor. Is this not the case and it’s actually just the commander pressure ? Do I need to connect up a fuel pressure gauge?

 

[Doubeleive]

Sure thing. Will do. I was under the impression that I was monitoring the fuel lift pump pressure output from a (low pressure/lift pump) fuel pressure sensor. Is this not the case and it’s actually just the commander pressure ? Do I need to connect up a fuel pressure gauge?

a physical gauge is best to rule it out for sure, just stick it up under the hood so you can see it through the window
and may as well do a fuel pressure drop test at the same time since you replaced the injectors