Stutter - Rumble

[ajwill]

2013 GMC Yukon Denali 6.2

Consistent stutter on incline. Started about a week ago. Previously had new plugs and wires installed (4months ago), trans flush and oil change (2 months ago). Almost due for another oil change as we’ve been driving it more. If I feather on the brake it continues to stutter going uphill or even at a slight incline. Sounds just like riding on a rumble strip.

Only times it stops;
1- foot off gas (coasting uphil)
2- foot heavy on gas
3- if in manual (m6) by downshifting to m5 (goes away momentarily then returns) downshift to m4 (goes away usually doesn’t return but obviously rpm and up.

258,000km on engine and trans, no major work other than the usual maintenance and repairs over the years. (Tires, rims, shocks, brakes, ac condenser, rad, bal joints, hubs, etc)

No dash lights come on. Ran for codes with nothing. One thing I noticed is sometimes (not always) when in stutter mode, either the rpm or spedo jumps around slightly.

Willing to try any suggestions. Just don’t want to cause more damage. Thanks!

 

[mikez71]

Set your cluster to display V4/V8 mode. See if it happens mostly in V4 mode..

Might be your AFM activating, and/or your torque converter slipping.

 

[ajwill]

Set your cluster to display V4/V8 mode. See if it happens mostly in V4 mode..

Might be your AFM activating, and/or your torque converter slipping.

Thanks, I will give this a try today and update. Really appreciate the post.

 

[petethepug]

258k on a 2013 Denali. Impressive. Do you know if the fuel pump has ever been replaced?

 

[ajwill]

258k on a 2013 Denali. Impressive. Do you know if the fuel pump has ever been replaced?

Yes it has been babied that’s for certain. I can confirm that the fuel pump has never been replaced.

 

[petethepug]

Check out rock auto and parts geek for an OEM acdelco or GM fuel pump / sender assembly with a lifetime guarantee. Also get a new carbon canister that rides next to the tank.

The f/p should have been replaced at 100k. Do it now as a safety measure. If engine power is lost at speed, power steering, power brakes go away. 3T doesn’t want to steer or stop without power.

Your mechanic may find the carbon canister has leaked its pellets into the fuel system. This requires the tank to be removed, swabbed out, lines blown out and f/p replaced.

Replace both as a two prong approach for safety, (much needed) deferred maint and prudence. A failing f/p or leaking carbon canister don’t usually throw a code. Have it scanned for codes before proceeding regardless.

 

[j91z28d1]

if you have a scanner that can read misfire data, pull up all 8 cyl on the screen and go drive making it rumble or whatever it's doing. if you see one or more cyl value constantly going up. that's atleast your cyl to start with. if it's not missing but rumbling on throttle up hill at low rpm. I might be something else. maybe drive train?

pushing the brake pedal lightly unlocks the torque converter. so that's helpful that's it's not the lock up cluch slipping and causing it. they some times shutter.

 

[petethepug]

Got one of these?

 

[ajwill]

Thanks, I will give this a try today and update. Really appreciate the post.

Ok so I have tried it. Seemed to be better for the first part of the drive (no stutter at all for about 10 minutes) but as soon as the incline increased a bit more it returned. Didn’t feel as bad though.

 

[ajwill]

Check out rock auto and parts geek for an OEM acdelco or GM fuel pump / sender assembly with a lifetime guarantee. Also get a new carbon canister that rides next to the tank.

The f/p should have been replaced at 100k. Do it now as a safety measure. If engine power is lost at speed, power steering, power brakes go away. 3T doesn’t want to steer or stop without power.

Your mechanic may find the carbon canister has leaked its pellets into the fuel system. This requires the tank to be removed, swabbed out, lines blown out and f/p replaced.

Replace both as a two prong approach for safety, (much needed) deferred maint and prudence. A failing f/p or leaking carbon canister don’t usually throw a code. Have it scanned for codes before proceeding regardless.

Thanks for this! I’ll make sure to replace these.