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2011 bogging down, hesitation,stutter.


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I just bought a 2011 Silverado 1500 LT 5.3L z71 it has the 3.42 gears. When ever I try to take off from a low speed/rpm’s the engine hesitates and just feels like it’s being held back til it hits over 2500rpms if I try to turn slow and go up a hill it will bog all the way up the hill unless I put it in Manuel mode and drop a gear to raise my rpms, it almost feels like it’s just in to high of a gear but there is still a hesitation when taking off its like the rpm’s get stuck for a second at a certain spot then it catches another thing idk if it’s related is when I put it in gear and let off the brake it will slowly accelerate on its own. When I bought it it showed code for map sensor replaced that no change, I updated driver side valve cover for new pcv design cause after first time I drove it home when I cranked back next morning  it blew smoke and could smell oil, new cover fixed that though. Everything on live data looks good and no codes except when it hesitates/bogs the spark advance is I’ll drop to between -1 and -6.5. Thought maybe cats stopped up so I removed them with no change. Anyone that can help give insight please let me know 

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Miles on truck?  

 

Any collapsed AFM lifter or spun lifter/worn cam noises?  Transmission fluid and filter ever changed?  Spark plugs oil fouled?  No other trouble codes?

 

You might try running some premium fuel with a couple bottles of Chevron Techron Fuel System Cleaner [same as GM fuel system cleaner, but available at Walmart and O’Reillys] (note not Techron’s similar fuel INJECTION cleaner) in it, and then giving it an “Italian tuneup”—some full throttle applications. Our ‘09 runs like a dog on regular fuel (even from Top Tier stations) but perks up on premium. I run a tank of fuel with Techron FS cleaner through our Silverado about every 3-4 months—among other things, it helps clean the AFM oil fouling off the spark plugs. 

 

Also, try running in manual mode on the transmission, with 4th gear selected as the top available gear. These trucks were programmed to shift up into 6th gear overdrive way too fast in the name of fuel economy instead of drivability, which can bog things down, especially on any type of incline when all fluids are not yet at full normal operating temperature. Be glad yours has the optional 3.42 rear gear; any bogging is even worse with the standard 3.08 gear. 

 

Be sure to run Dexos1 rated synthetic motor oil (to help prevent piston ring fouling, blowback, and PCV problems) with a good quality oil filter, and consider a Range module or PCM tune to turn off AFM as soon as possible to lessen the chance of any future AFM problems. Most of us that turned off AFM noticed little if any change in fuel economy. 

Edited by MaverickZ71
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There’s no lifter noise or anything like that, the truck has 211,000 on it. Right before I got it the carfax shows the transmission fluid was changed filter changed and then about a month later shows the transmission cooler being flushed. It runs better in manuel mode, and it run perfect like it should in tow/haul mode, accept it will downshift to soon and it will jerk the truck back some and shoot the rpm’s up real high, but upshifts perfect. It did show a misfire on #8 once but went away on its own as soon as it came but I replaced the plugs anyway with pregapped ac delco ones. And the only other code it’s ever showed was for map sensor and I replaced that but it didn’t change anything 

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Sounds like you’re on top of that other stuff, and the problem is really transmission related. Maybe a transmission-related drivability issue is why why the “cooler was flushed” after the filter and fluid change, and why the truck was sold. There are those on here that say if you don’t change the transmission fluid and filter according to the severe maintenance intervals, even in normal use, there will be later ramifications, usually internal wear that can lead to slipping. If not ever changed until high mileage, it has been recommended not to change it at all, because the new slick fluid combined with the worn parts may very well result in slippage. Some have even drained the new fluid and refilled with the old (filtered) fluid to continue driving. Mechanic Scotty Kilmer on Youtube talks a lot about this. 
 

Hopefully one of the GMT900/transmission/torque convertor experts on here can chime in with more ideas for you. If not, you might repost directly under the “Ask the GM technician” section. 

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It does kinda feel like it is transmission related, but im hoping it can be tuned and the shift patterns be changed or tweaked a little and fix it because I can put it in tow haul where the patterns change and it runs great for the most part there’s still a partial engine stutter but that’s rare and it always shifts smooth as can be no flares or hard shifts or any clunking, and I crawled up under and looked at everything and honestly compared to the rest of the undercarriage the transmission looks new, but idk. I figured I’d call the shop that done the transmission service and see if they can pull up records on why they don’t what they did.

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Sounds like a plan.

 

FYI, I removed the Range AFM-delete module from the OBD-II port on our ‘09 Silverado (5.3L, 6L-80E) and replaced it with Hypertech Max Energy 2.0 programming, looking forward to “improved performance” with the premium fuel tune. The only perceived difference was immediately the transmission flared shifts and slipped. That was at 60k miles. Put it right back on factory tune, and there was never any more flaring or slipping.

 

Like they say, your mileage may vary. Hope you can get it fixed and enjoy your truck. 

Edited by MaverickZ71
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