Hey all. We just bought a 2011 Suburban two weeks ago, and are already having some potential issues. Bought it from a reputable dealer, but as-is, since it’s 13 years old and has 126k on the odometer. I’m new to Chevy trucks, but have been working on my own vehicles for over 20 years. Not a master mechanic by any stretch of the imagination, but know enough to at least consider tackling intermediate auto projects.

So on to the issue, we bought the 2011 Suburban after my wife’s 2011 Explorer crapped the bed. We didn’t have the luxury of time, because she needed a vehicle to tote the kids around in, so we took the plunge without doing weeks of research. Hopefully we didn’t jump the gun too much.

So here we are two weeks after purchasing, and we are coming home from my father in laws house. Trucks starts acting a little weird between 35-50MPH. The transmission seems like it can’t figure out which gear it wants to be in. Transmission is sort of jumping up and down. RPMs are bouncing up and down. A little bit of hesitation when pressing the gas. Some slight bucking, but only slight. I’m leaning toward the AFM system being wonky, but I’m wondering if it could be something else.

Quick google searches result in AFM issues showing similar symptoms to what I am experiencing. But I don’t know if I’m missing something else.

Any suggestions on how to test if it’s the AFM or something else?

Thanks in advanced,
Rob


Edit: also, RPMs and everything else feels normal when idling, and when coasting. But as soon as I start to accelerate and get to around 35MPH, that’s when the “shift” issues start.

Edit 2: also, no check engine lights or other warning lights present.

 

I am sure someone else will correct me if I am wrong, but I think if you were experiencing AFM issues, the main thing is failure of the valve lifters, due to the AFM "fuel saving" mode turning off cylinders, and lack of lubrication to those valve lifters while those cylinders are disabled. I think the first symptom is engine noise due to the failing lifters, not issues with the way the transmission shifts. But that is just me reasoning through things, and not based on experience.

My 2003 Yukon had the transmission start experiencing shift issues around 130k miles, and I ended up having to get the 4L60E transmission rebuilt, when it was only 8-10 years old, and it happened when I was hauling a bunch of 9th grade boys around town.

I would start by running the engine in park, and see if you notice any unusual engine noise, knocking type sounds for example, when revving the engine in park. There should be some Youtube clips out there that show what the AFM induced lifter failure sounds like.