Engine stalling, rough idle, rpm fluctuation.

[abdullah_Zahra]

2010 Suburban. I don't know if the correct term to use here is "stalling" I will try and explain what happens.
Car's idle is a tiny bit rough, barely noticeable. When I am cruising at low speeds (1st +2nd gears) and after immediately letting go of the gas pedal, the car will start to kinda "jerk" you could say, giving me the impression as if someone was to hit me from the back. I'd be going back and forward in my seat while this happens
When I lightly press on the brakes during this episode, the car will slow down perfectly no issues whatsoever. Please note this is not a transmission issue. I don't have any problems in gears going up and down at all.
The problem will mostly occurs when I successfully go from 2nd to 1sr, at around 1200-900 RPM. During the episode, the RPM needle will not go down smoothly. As if the car is going through hiccups.
Not to mention that overall, I feel like the engine's power and responsivity aren't what they used to be.

No check engine light, once scanned, I found p0174, p0171 codes stating a lean condition. but those codes weren't pending, they only lasted a day or two and then they were gone.
I thought of cleaning MAF, throttle body, maybe injectors and changing coils and plugs. Anything else I should check?

 

[Marky Dissod]

You say this is NOT a transmission issue. Can you duplicate symptoms in neutral?
If so, seriously consider checking / replacing throttle body assembly and associated wiring.
Remember, your car has an electronic signal throttle (not a physical cable),
so the ecm can second guess or even countermand your foot's orders.

You can also try adding 2x normal fuel system cleaner to several gas tanks.
(If you run E85, don't double dose.)

How many miles on the O2 sensors?

Before firing the parts cannon, fire the parts derringer:
Replace the oldest cheapest and easiest parts first.

 

[donjetman]

If its throttle body to pedal miscommunicating it would throw a P2135 code.

 

[abdullah_Zahra]

You say this is NOT a transmission issue. Can you duplicate symptoms in neutral?
If so, seriously consider checking / replacing throttle body assembly and associated wiring.
Remember, your car has an electronic signal throttle (not a physical cable),
so the ecm can second guess or even countermand your foot's orders.

You can also try adding 2x normal fuel system cleaner to several gas tanks.
(If you run E85, don't double dose.)

How many miles on the O2 sensors?

Before firing the parts cannon, fire the parts derringer:
Replace the oldest cheapest and easiest parts first.

I say this is not a transmission issue because the transmission was completely rebuilt 6 months ago. When the issue started rising a couple of months back, I figured it had something to do with the tranny, so i took it to the same shop. He drove it around and told me it can't be the transmission as he changed every single thing brand new.
Regarding the o2 sensors, I have no idea as the car was purchased second hand (only drove it for 5-6k miles so far) it has about 102k miles now.

 

[Marky Dissod]

I say this is not a transmission issue because the transmission was completely rebuilt 6 months ago.
When the issue started rising a couple of months back, I figured it had something to do with the tranny, so i took it to the same shop.
He drove it around and told me it can't be the transmission as he changed every single thing brand new.

I remember saying the same as above about an LT1 Caprice wagon I once owned. 8 months after that rebuild, he re-rebuilt it.
Assuming you have better luck than I did, and you don't have to beat him with a rubber hose til he re-rebuilds it,
O2 sensors are supposed to be replaced every 100,000 miles or so.