Stumble at part throttle, no codes: It's the torque converter

[John H Daniel]

My 2011 Denali has started an annoying stumble at part throttle.
So under light load, in any gear, with just enough throttle to accelerate, but not shift down, the engine will stumble/miss/hesitate. Down shift to higher revs, its smooth, no problem.
I noticed it first while towing; when cruise control is trying to add speed before needing to down shift.
No codes, fuel pressure is good, new plugs, air filter; tried injector cleaner, cleaned throttle body, checked for vacuum leaks.

Any ideas?

 

[Geotrash]

My 2011 Denali has started an annoying stumble at part throttle.
So under light load, in any gear, with just enough throttle to accelerate, but not shift down, the engine will stumble/miss/hesitate. Down shift to higher revs, its smooth, no problem.
I noticed it first while towing; when cruise control is trying to add speed before needing to down shift.
No codes, fuel pressure is good, new plugs, air filter; tried injector cleaner, cleaned throttle body, checked for vacuum leaks.

Any ideas?

How many miles on it?

 

[John H Daniel]

198,000. I've had it last 20,000.

 

[Doubeleive]

Might be time for a new maf, also cleaning the throttle body does not always fix all issues they wear out, mine was doing something similar and I changed the throttle body to a ls3 type since I was replacing it anyway and the problem went away

 

[Fless]

Have the accelerator pedal position sensor and the throttle position sensor been graphed (for smooth tracking) and compared?

 

[John H Daniel]

Have the accelerator pedal position sensor and the throttle position sensor been graphed (for smooth tracking) and compared?

No

 

[Geotrash]

+1 for the MAF.

 

[gpracer1]

Could be all those ideas but you will need scanner of some sort to log data. If it were me I would watch the O2 sensors switching and then see if either or both banks react to the problem happening. That way you can rule out one side or common sensor.

 

[2K8Lade]

+1 for the MAF.

Any way to tell if it's bad? I'm still trying to figure out my issues and I saw the MAF readout of like .10 to .17 lbs/s or something like that. No idea what the normal number is.

 

[John H Daniel]

I went after the ignition and intake stuff many folks have done. Nothing helped.
With more research, I settled on the torque converter shudder/ failing TC/ lockup clutch.
I was hoping to just replace the TC, but was concerned that its failing many have shed metal particles. So I connected a hose I use to change fluid to the trans oil cooler and pumped out a cup or so.
Yep, metal in the cup.
So rebuilt trans, TC and are about to happen. Good time to replace that leaking rear main seal as well.

 

[Throttle Boss]

Experienced all of the above symptoms over a 6 month period. 2016 Tahoe Lt w/ 110,000 miles. It was a bad torque converter and stock transmission fluid was not compatible per the Technical Service Report. Research your vin number for recalls and TSRs.

 

[robgreg75]

I went after the ignition and intake stuff many folks have done. Nothing helped.
With more research, I settled on the torque converter shudder/ failing TC/ lockup clutch.
I was hoping to just replace the TC, but was concerned that its failing many have shed metal particles. So I connected a hose I use to change fluid to the trans oil cooler and pumped out a cup or so.
Yep, metal in the cup.
So rebuilt trans, TC and are about to happen. Good time to replace that leaking rear main seal as well.
View attachment 375476

My torque converter did the same thing. I was on a trip and drove it the 5 hour drive back home. Mine spit so much metal into the tranny that the tranny would not stay engaged at idle. While I ordered parts I had to change my idle speed to like 800 rpm so the transmission wouldn't violently engage as the revs came up. I rebuilt the tranny with one of those sonica upgrade kits, 80,000 miles later and still working perfect.

 

[John H Daniel]

My torque converter did the same thing. I was on a trip and drove it the 5 hour drive back home. Mine spit so much metal into the tranny that the tranny would not stay engaged at idle. While I ordered parts I had to change my idle speed to like 800 rpm so the transmission wouldn't violently engage as the revs came up. I rebuilt the tranny with one of those sonica upgrade kits, 80,000 miles later and still working perfect.

Good to know... Yeah, last couple of days, mine was requiring revs before finally engaging with a jerk, leaving a stop. I've gotten pretty bold with the rolling "stops."
I don't have the resources to pull and rebuild it myself, so will go to Aamco or see if my local guy can do it.

 

[John H Daniel]

Good to know... Yeah, last couple of days, mine was requiring revs before finally engaging with a jerk, leaving a stop. I've gotten pretty bold with the rolling "stops."
I don't have the resources to pull and rebuild it myself, so will go to Aamco or see if my local guy can do it.

 

[robgreg75]

Good to know... Yeah, last couple of days, mine was requiring revs before finally engaging with a jerk, leaving a stop. I've gotten pretty bold with the rolling "stops."
I don't have the resources to pull and rebuild it myself, so will go to Aamco or see if my local guy can do it.

I am currently building a house and will have a lift when move but when I did mine I had to do it in the garage on jack stands in September in Texas so yes it was pretty miserable to do.

 

[John H Daniel]

I am currently building a house and will have a lift when move but when I did mine I had to do it in the garage on jack stands in September in Texas so yes it was pretty miserable to do.

Man, that was a job! I can't imagine getting all that drivetrain back in place.
I figure I've already spent enough time on the pavement/dirt/concrete under cars that I don't feel too bad about farming out the major stuff.

 

[robgreg75]

Man, that was a job! I can't imagine getting all that drivetrain back in place.
I figure I've already spent enough time on the pavement/dirt/concrete under cars that I don't feel too bad about farming out the major stuff.

And mine is 4 wheel drive so that extra stuff too, the rebuild wasn't too bad to do it was my first time rebuilding an automatic so I was probably a little slow. I pulled it in the garage on Friday and was done by Monday. I bought a Cadilac CTS with a tranny leak, I towed it to my buddies shop that has a lift it was so much easier/less painful.

I know what you mean but I just refuse to pay someone for something I can fix myself.