Engine Stuttering at ~1500 RPMs

[gfleck]

Hey everyone I've looked here and not found any definitive answers on what might be causing this. The vehicle is my 2012 Suburban LT 2WD 5.3L. About 185k miles on it. It is bone stock except for retrofitted headlights and an extra engine to frame ground cable. Oil is changed religiously.

The engine idles okay but on moderate acceleration there is a stuttering around 1000-2200 RPMs. Each time it is a slightly different range of approximately 200RPM within that boundary. The RPM's will flutter up and down a little and there will be a slight loss of power. At first I thought it might be bumps in the road.

There were some old P0300 codes but no misfires when it is actually happening. I had the engine mounts replaced about 1000 miles ago. I believe that it could have been happening before that.

On here I've seen folks saying this type of issue could be any mix of misfires, intake leaks, fouled plugs, fuel pressure regulator, or torque converter/transmission issues. What do you think?

I've cleaned out the throttle body already, but I'm not sure what to try next. I need your wisdom! Should I put in some Lubegard Instant Shudder Fix to see if it's the torque converter/transmission?

Have you checked the throttle position sensor (TPS)? I did not experience all that you describe, but I did sense hesitation at low rpm's and a low engine output condition. Engine monitor clearly showed worn TPS potentiometer.

 

[headala]

So, an update on this:
I replaced all the plugs and wires. The 8th one looked like it had never been replaced. This didn't change anything, but I'm glad I did it.

Drove up to Birmingham, the stuttering kept getting worse and worse, and I noticed my gas mileage was awful just going down the road. When I put the truck into "tow mode" (shifted down a gear), the mileage improved. That was the last clue for me that the torque convertor was bad and the transmission was slipping.

Took the truck to the most honest transmission guy in Birmingham. He's a wizard. Drove it 5 miles and diagnosed it immediately. Said he could rebuild it, or I could "Go and get myself a cheap and easy junkyard tranny" but he didn't recommend that route. I told him "that doesn't mean what you think it means these days" :-D

Had him rebuild it. Slipping and stuttering was all gone. Shifts like a dream, very smooth, both the parts and labor are warrantied. But there was still a bit of hesitation when I hit the gas.

Tonight we replaced the Throttle Position Sensor. That was the last piece of this issue.

Truck runs like a dream now. Responsive and smooth.
You guys are all amazing. Thank you for all the help!

 

[Dustin Jackson]

@headala Thank you posting an update, glad it all worked out!

For reference, what transmission did you have and how much was the rebuild cost?