Stalling

TravisK · March 31, 2023

2015 Silverado 5.3l 6 speed transmission stalling issue.

Was intermittent. Once every few days when coming to a stop it would randomly stall. Twice now, one night about a month ago then again today its continuous and replicate-able . After further testing. And no codes being thrown.

I've notice if I put it into manual and only let it shift to 2nd I can stop and go without a stall.

After coming to a stop without a stall if I shift it to allow 3rd gear it will clunk like it just shifted into 3rd even at a complete stop and begin to either shutter and sputter or go ahead and just stall completely.

Also noticed if I ever so slightly keep my foot on the accelerator while coming to a stop the stalling issue doesn't happen, and after comming to a stop i can take my foot off the accelerator and continue normally.

Also I had pulled the battery cable hoping to reset whatever was causing it and had actually made it worse where the transmission was completely slipping and would barely allow the truck to go, seemed like it would begin working normal at higher rpms.. After driving at highway speeds I think that may have worked its self out. Still continues to die when stopping.

rav3 · March 31, 2023

You didn't mention your miles but I will assume that it's probably around 100k. Do you have any codes? My guess is that it may be your throttle body is carboned up.

It could be other things but without any code information, it's just a guess. Search youtube for throttle body cleaning

TravisK · March 31, 2023

Correct, about 115k. Throttle body actually looks kinda new and I have already done a cleaning. Dirty TB really cause such a intermittent issue? Was thinking more on the electronics side. Possible failing throttle position sensor. Only seems to start acting up after reaching operating temp. Jumped in it this morning was going to run it to the dealership and ofcouse it's not doing it now... Just trying the narrow it down, and hopefully eliminate the likelihood of a failing transmission. Would a throttle body issue really cause transmission slippage, not downshifting or upshifting correctly and not fully engaging gears or delayed engagement?

Also forgot to mention that I bought it at a dealership over a month ago. Tried taking it back up there to have it diagnosed the morning after it was continually happening and ofcouse they couldn't diagnosing since it wasn't still happening. Don't know the full history on it and the new looking throttle body makes me think someone at some point thought that might be the issue as well.

Edited March 31, 2023 by TravisK

rlcole321 · April 2, 2023

One other thing to look at, your EVAP system, you may be getting raw fuel in the intake when you come to a stop, with the throttle closed. it will stall the motor, that would also explain why if you give it a little throttle it doesn't stall. Are you one to fill your tank with as much as you can?, if so then your canister is probably saturated. That would explain no codes.

TravisK · April 7, 2023

On 4/1/2023 at 9:48 PM, rlcole321 said:

One other thing to look at, your EVAP system, you may be getting raw fuel in the intake when you come to a stop, with the throttle closed. it will stall the motor, that would also explain why if you give it a little throttle it doesn't stall. Are you one to fill your tank with as much as you can?, if so then your canister is probably saturated. That would explain no codes.

I do fill the tank, but not keep pumping it untill its absolutely full. usually after the nozzle kicks off the first time I stop. one thing I have noticed is that the cap is super duper tight when I get ready to put gas in, like as in there would be no way my old lady could put any gas in it if she had too. And I only ever just do a one click tightening. When you say the canister is saturated you mean i should be able to pull it off and dump fuel out of it?

rlcole321 · April 7, 2023

the evap lines are plastic and kind a brittle, if you can disconnect the line from the eng side (evap solenoid) and the canister under the rear of the truck and blow it out to see if fuel is in it. go to youtube and search for evap sol. and canister for location,

TravisK · April 8, 2023

Wouldnt just pulling the line off at the purge valve at the engine tell me if that's the issue if it continues to stall? Is that how the supposed extra fuel is getting to the engine through the EVAP system? If so then that's not the issue because it continues to stall in the same manner.

TravisK · June 16, 2023

update and other issues now.

Shop I bought it at ended up paying a Chevrolet dealership to diagnose and repair the issues. which ended up in a complete transmission replacement.

Went to pick it up today. Drove it across the metroplex about 150 miles. On the way back we had stopped to look at our old apartment and noticed it kinda sputtering a little when i stopped in gear. Was thinking oh great that didn't fix the issue altho it never stalled and felt different than it was doing before... started and stopped a few times still sputtering. Hesitated to take off initially. Started and stopped a few more times, put it in park and it was still sputtering. Then the check engine light popped on with cylinder 4 misfire p0304 code. After i took off and got back on the highway and the code went away shortly after but it still felt like it was missing or the transmission was being kinda herky jerky especially when letting off the gas then reapplying slightly.

I understand they have to relearn but I was thinking that was just for shift points (definitely wasn't shifting 100% correctly, however I'm attributing that to the relearn). Would a new transmission be causing the misfire or the jerkiness? Is that something the relearn process would also clean up? Never had the check engine light come on since i bought it. Find it very odd that it comes on right after a transmission is put in it.

Edited June 16, 2023 by TravisK

OffTheAir · June 17, 2023

6 hours ago, TravisK said:

update and other issues now.

Shop I bought it at ended up paying a Chevrolet dealership to diagnose and repair the issues. which ended up in a complete transmission replacement.

Went to pick it up today. Drove it across the metroplex about 150 miles. On the way back we had stopped to look at our old apartment and noticed it kinda sputtering a little when i stopped in gear. Was thinking oh great that didn't fix the issue altho it never stalled and felt different than it was doing before... started and stopped a few times still sputtering. Hesitated to take off initially. Started and stopped a few more times, put it in park and it was still sputtering. Then the check engine light popped on with cylinder 4 misfire p0304 code. After i took off and got back on the highway and the code went away shortly after but it still felt like it was missing or the transmission was being kinda herky jerky especially when letting off the gas then reapplying slightly.

I understand they have to relearn but I was thinking that was just for shift points (definitely wasn't shifting 100% correctly, however I'm attributing that to the relearn). Would a new transmission be causing the misfire or the jerkiness? Is that something the relearn process would also clean up? Never had the check engine light come on since i bought it. Find it very odd that it comes on right after a transmission is put in it.

Hey Travis,

I have had preventative maintenance done on my 6L80 prompting the relearn process, and it was never anything more than maybe a subtle difference, barely even noticeable, for the 100-200 miles or so it took to learn my driving patterns. It would not have such a significant impact on your ability to drive the truck.

Now, coincidences do happen, it is very possible for one thing to break right after another. But in your case, I'd say the chances are pretty astronomical. The way you describe it, it almost seems like there is some sort of disconnect with that transmission replacement; something is not lining up.

Have you considered going back to the Chevy dealership that did the repair? To diagnose and perform a transmission replacement is a pretty hefty price, I would like to imagine you would've liked that to have fixed the problem you have been dealing with.

TravisK · June 17, 2023

13 hours ago, OffTheAir said:

Hey Travis,

I have had preventative maintenance done on my 6L80 prompting the relearn process, and it was never anything more than maybe a subtle difference, barely even noticeable, for the 100-200 miles or so it took to learn my driving patterns. It would not have such a significant impact on your ability to drive the truck.

Now, coincidences do happen, it is very possible for one thing to break right after another. But in your case, I'd say the chances are pretty astronomical. The way you describe it, it almost seems like there is some sort of disconnect with that transmission replacement; something is not lining up.

Have you considered going back to the Chevy dealership that did the repair? To diagnose and perform a transmission replacement is a pretty hefty price, I would like to imagine you would've liked that to have fixed the problem you have been dealing with.

Ya, in dropped it back off there about 2 hrs after I picked it up. Ofcouse my service rep went home early for the day. And the guy I dropped it off with seemed kind of annoyed I was dropping it off before the relearn process had a chance to relearn. He was trying to say 500 miles. I told him it wasn't running like crap on the highway when I dropped it off and I never had the check engine light come on before even with the stalling issues I was having that they diagnosed as a transmission problem. Guy said it would be Monday before my service rep got back and that would be the earliest they could look at it. Aggravates the piss out me that they didn't test drive it before saying it was ready. Can just already hear em trying to convince me its just part of the relearn process or that it's just a total coincidence that I'm starting to experience a totally different can of worms problem after they fixed my other one..

mikeyk101 · June 17, 2023

That really sucks... I'm kind of surprised though that @GMCustomerService hasn't dropped in on this thread to give you one of their worthless replies and tell you to contact them about the problem...

TravisK · July 5, 2023

Just wanted to update if anyone cared. After immediately returning to the shop after the transmission repair/replacement because of rough idle / misfire issues along with ac issues that mysteriously developed while in the shop for transmission replacement not to mention the dead battery from a roku device being left plugged in that they diagnosed as a bad battery because they couldn't simply jump it with their jump box (another $300 + fees)..

I ended up pulling it out out to try and resolve the misfire issue myself after they were unwilling to stand by any diagnosis of the rough idle (basically wanting to throw parts at it until it was fixed, something I could do much cheaper on my own. The fix ended up being plugs and wires which was actually overdue) and also after the shop had it two weeks working on the ac issue which they diagnosed as a leaking compressor to evap line and bad compressor which they billed and replaced (over $2k in repairs, little more than half covered by warranty services) with the ac STILL ONLY blowing vent temps of 60+ degrees and only on the highway. Taking it back today to let them take another stab at the a/c. Service rep knew it wasn't working right when he turned it loose knowing it was coming back even tho on the paperwork says it is. Looks like they're trying to cover themselves from a misdiagnosis on the a/c. See what happens. Wish someone from gm would actually look into this fiasco of a repair. 10k+ and two months later my truck still isn't right.

Edited July 5, 2023 by TravisK