Engine 'Stumbles' When When Accelerating

[PNW_IT_Guy]

My 2010 Yukon SLT 5.3 has a weird issue that I haven't been able to find anything online that's exactly the same. When I'm approaching an on-ramp and I hit the gas, sometimes I can feel the transmission downshift, then the engine revs up and starts to accelerate, but then it just... pauses for a moment. It's just a moment then it gets right back into and goes. Maybe I'm just not searching for the right word. It's not that it generally 'runs rough' but smooths out when accelerating, it's not that it's always rough when accelerating, it doesn't die completely and need to be restarted.

It'***** it, downshift, pause, go. It does seem to have a slightly rough idle, but generally seems to run reasonably well.

Also, no lights on the dash at all. Transmission was drained and filled and oil changed just this past fall. It's a used truck that I bought with 180k a bit more than a year ago. Hopefully I've answered all the basic questions. Thoughts?

 

[Marky Dissod]

1st thought:

It'***** it, downshift, pause, go.

What did you say? This forum operates under the assumption that words hurt.

2nd thought: Before you fire the parts cannon, consider firing the parts derringer, crank & cam position sensors.
Clean the MAF sensor.

3rd thought: Can you get someone (preferably a tuner) to sit next to you with their laptop hooked up to your OBD2 port,
reading the realtime telemetry as you drive, especially as this peculiar behavior exhibits itself?
Before you drive off, check the throttle position sensor for linear response.

 

[PNW_IT_Guy]

geez, sorry I guess I missed a space at the worst time. *hit it, not what they thought i said.

Crank and cam sensors aren't too spendy, so I guess I could try that. But shouldn't I get a check engine light if they are bad? I think I have cleaned the MAF sensor but it's been a year so I could give it another go.

I wish I knew a tuner. I do have the Torque app so I'll check to see if it shows throttle position. Pretty sure it does.

Thanks for the input!

 

[Marky Dissod]

You get a Check Engine light if they are bad ENOUGH. If they're not good, yet not bad enough,
you can get problems like this.

 

[intheburbs]

180k? Have you done anything with the fuel system? Before just throwing money/parts at it, I'd run some Techron or BG44 through it. Maybe more than once.

 

[Doubeleive]

My 2010 Yukon SLT 5.3 has a weird issue that I haven't been able to find anything online that's exactly the same. When I'm approaching an on-ramp and I hit the gas, sometimes I can feel the transmission downshift, then the engine revs up and starts to accelerate, but then it just... pauses for a moment. It's just a moment then it gets right back into and goes. Maybe I'm just not searching for the right word. It's not that it generally 'runs rough' but smooths out when accelerating, it's not that it's always rough when accelerating, it doesn't die completely and need to be restarted.

It'***** it, downshift, pause, go. It does seem to have a slightly rough idle, but generally seems to run reasonably well.

Also, no lights on the dash at all. Transmission was drained and filled and oil changed just this past fall. It's a used truck that I bought with 180k a bit more than a year ago. Hopefully I've answered all the basic questions. Thoughts?

I would say clean the throttle body, maf, new air filter. then either some injector cleaner back to back for a few tanks of gas or injector cleaning service.
see how that pans out....
also get a tune, it makes a difference and can get a buggy shift like that addressed.
if i was going to throw parts at it I would do the maf and throttle body @180k they are both questionable in my eyes and directly correlate to shifting & stumbling.
a drive recording with a scanner is always a good idea.
and the question that should be asked is what maintenance has been performed already?
bought it used @180k
changed the oil
changed the transmission fluid
and???? anything else? plugs/wires?, 02 sensors?

 

[PNW_IT_Guy]

I have been thinking about doing the air filter. It doesn't look too bad but it's also pretty cheap. I'll look into just replacing the MAF. I'd love a tune but don't really know what all goes into doing that... seems like it would be expensive.

Sorry for not giving more details on my servicing:
-Several fuel system cleanings in past year, Even ran a tank of E85 through it. (Gas mileage is down around 13mpg so I've been trying everything I can think of to improve that)
-2 or 3 oil changes in the past year with Mobil1 Full Synthetic
-Oil flush on last oil change
-Transmission drain/fill in December using Mobile1 Full Syn ATF
-MAF cleaning a year ago
-Throttle body cleaning a year ago
-Removed fuel pump ground, cleaned surface of rust and replaced. (Significant surface rust over entire undercarriage)

I have plans to do a big 3 upgrade and clean all grounding connections in the engine bay.