2018 Silverado 5.3 Z71 6L80E - Eight miles from home, I had the water pump begin to fail. Replaced pump and thermostat. Drove fine. Made 180mi trip and had engine miss and lower gas mileage

[Roadblock_70]

Hello all.

 

After the south received an artic freeze my battery was dead and I had to use a jumper box to start it. Everything seemed ok.

 

I drove it to TSC and then I am 9 mi from home. I hear the vehicle info warning dashing noise- and look down. "Engine overheating stop and idle." I realized because temps had been down to 9* in the NC mountains the thermostat might have stuck open or be screwed up. I find a place to pull off and I am letting it idle but it was headed to 260. I cut the engine off. It was still ambient temp of 43* I waited 30 minutes, drove 3 miles and I heard the same warning noise- I got one more mile and pulled off. Let the engine completely cool- yes the fans ran after shutdown both times. Now 5 mi from home, turn on engine, it was cooled off, I drove 3 mi, heard the noise, saw the temp gauge headed 230+ stopped, turned the engine off.

 

I live in an area where there is one towing company, they have a monopoly, they will skull screw you and they will leave vehicles on the side of the highway despite telling you that they will tow you.

 

I called anyway because I could not afford my engine screwed over. I waited 1 hour for them to come and then drove the last 2 or 3 mi home and as I got there the temp began to rise above 230 and I shut it off and coasted it into my driveway.

 

I ordered a new water pump, new thermostat, and I changed them out. Thermostat was stuck, water pump bearing was shot.

 

I completely backflushed and then replaced the coolant.

 

I did an oil change- I do oil changes every 4000 mi, the truck has 136,000 mi

 

I drove 75 mi to Alpharetta, truck was at 210* max heat. Drove 75mi back home. No overheating and no performance problems.

 

I drove yesterday 90 mi one way and I had no problems. It cooled 1hr 30m while I was in an MD appointment.

 

I was down to 1/4 tank gas and I began looking for a station to fill up and my truck felt like there was a miss however there were no codes pulled, I checked with an ELM module. I filled it up with 91 ethanol free and put some seafoam in the tank as I didn't know what was going on and I could not tell if it was a miss or the AFM/DOD or what.

 

It drove ok but I had been getting 17mpg per the fuel use calculator- ever how accurate that is- and it was now reporting 15mpg.

 

It is a 2018 Silverado 1500 LT with a 5.3 V8 and 6L80E, has Z71 package.

 

 

[asilverblazer]

Quote

 

...my truck felt like there was a miss however there were no codes...

 

It drove ok but I had been getting 17mpg per the fuel use calculator- ever how accurate that is- and it was now reporting 15mpg.

 

I think the symptoms need to become more pronounced for a more accurate diagnosis.

[Roadblock_70]

It seemed as though there was an miss in the engine- as in it was not firing on some cylinders. No codes pulled by my ELM. I have an AFM/DOD shutdown on the truck via OBD2-  so as to avoid any further damage to the engine from AFM/DOD

 

In the last 48 hours it has had this behavior where I will be driving and begin uphill, the engine stumbles and it will rev from 1800rpm to 3000rpm or 1600rpm to 3800rpm. Truck is in drive mode, truck has done it on a hill and on perfectly flat land paved road

 

What other information do you need for moving forward ?

 

[asilverblazer]

On 2/13/2025 at 11:28 PM, Terrapin_W_N_C said:

It seemed as though there was an miss in the engine- as in it was not firing on some cylinders. No codes pulled by my ELM.

Then its not a miss. See next.

 

On 2/13/2025 at 11:28 PM, Terrapin_W_N_C said:

I have an AFM/DOD shutdown on the truck via OBD2-  so as to avoid any further damage to the engine from AFM/DOD

Take this off. In order to diagnose (including OBD) eliminate unknown variables. No telling how the device keeps the DOD from functioning, but it certainly won't help.

 

On 2/13/2025 at 11:28 PM, Terrapin_W_N_C said:

In the last 48 hours it has had this behavior where I will be driving and begin uphill, the engine stumbles and it will rev from 1800rpm to 3000rpm or 1600rpm to 3800rpm. Truck is in drive mode, truck has done it on a hill and on perfectly flat land paved road

 This sounds transmission related - your code reader may not be picking up all trouble codes.

 

Given how hot it got, inspect the transmission fluid. Consider a flush, it might be cooked.

 

Is the check engine light on?

Can you monitor torque converter lock up?

Edited February 19, 2025 by asilverblazer

[Roadblock_70]

It was the 6L80E that grenaded at 135,400mi

[mikeyk101]

28 minutes ago, Terrapin_W_N_C said:

It was the 6L80E that grenaded at 135,400mi

I feel your pain. At least in your case, you did get some kind of symptoms that it was going bad. In my case, last year at around 95k miles, one minute I was moving just fine. Next minute, I tried accelerating but truck just kept slowing. I had to pull to side of road.  Worst part was I was in the middle of nowhere, 10 miles outside of Valley, AL on a back road, 860 miles from home. Yay!!!

[Roadblock_70]

1 hour ago, mikeyk101 said:

I feel your pain. At least in your case, you did get some kind of symptoms that it was going bad. In my case, last year at around 95k miles, one minute I was moving just fine. Next minute, I tried accelerating but truck just kept slowing. I had to pull to side of road.  Worst part was I was in the middle of nowhere, 10 miles outside of Valley, AL on a back road, 860 miles from home. Yay!!!

 

Mine went out at West Point GA just above Valley. I was trying to get on Hwy 29 N to avoid night time construction on I-85 N. The trans light flickered and I had intermittent problems going home, but the trans fluid temp was not way out of line.

 

If you know where Fob James drive is in Valley, that is where the transmission first flashed the D light. I managed to get it home to western NC, I asked around who did good rebuilds on transmissions and I was told that this shop was very competent. I took it to them and the only thing I authorized was a transmission rebuild.

 

They thought they could dick me around, they took both fans from behind the radiator. They have one fan hung from the shroud and it is off an inline 4cyl.

 

They disabled the DOD without asking me. They screwed with the tire size, because the 18" tires on my truck are the factory size exactly so now the speedometer is screwed up. I think that from the PCM, with the kind of software they used to disable DOD, they may have done something with the cooling fan programming.

 

I am going to do a chargeback and fight this.

 

[mikeyk101]

4 hours ago, Terrapin_W_N_C said:

 

Mine went out at West Point GA just above Valley. I was trying to get on Hwy 29 N to avoid night time construction on I-85 N. The trans light flickered and I had intermittent problems going home, but the trans fluid temp was not way out of line.

 

If you know where Fob James drive is in Valley, that is where the transmission first flashed the D light. I managed to get it home to western NC, I asked around who did good rebuilds on transmissions and I was told that this shop was very competent. I took it to them and the only thing I authorized was a transmission rebuild.

 

They thought they could dick me around, they took both fans from behind the radiator. They have one fan hung from the shroud and it is off an inline 4cyl.

 

They disabled the DOD without asking me. They screwed with the tire size, because the 18" tires on my truck are the factory size exactly so now the speedometer is screwed up. I think that from the PCM, with the kind of software they used to disable DOD, they may have done something with the cooling fan programming.

 

I am going to do a chargeback and fight this.

 

 

Ha! FOB James is where King Chevrolet is at right off I-85. That's where I had the work done. The trans problem happened on a Thurs morning. The tow company had me towed there. Luckily I had met up with my buddy the night before and he was tailing me. We left the truck there and spent weekend down in Moultrie GA for a planned gathering.

 

Meanwhile King Chevy worked on getting a remanufactured delivered which they got by Sat. My buddy dropped me off on the way back  Sat evening at the Quality Inn right across the street. By Mon early afternoon I was headed back to Wisconsin with the swap done. Mine didn't end up with any problems and a year later, I'm still good.

 

Man that's a shame what that shop did to you. I would absolutely fight it as well. I don't know how they even thought they could get away with doing all that. It sucks when you pay good money to get such shoddy work from a place. I hope you are able to get a resolution out of this and get things running the way they should.