Jump to content

Engine Revs to Redline on Cold Start 6.2L

Denny NWO
 Share

Recommended Posts

Rob Mugs Enthusiast

Rob Mugs

Posted
Posted

That's crazy, almost reminds me of a runaway diesel.

 

I'd definitely bring that in

  • Replies 52
  • Created
  • Last Reply

Top Posters In This Topic

Popular Days

Top Posters In This Topic

Popular Days

Popular Posts

Denny NWO
Denny NWO

It's been a week with the monitor connected to the OBDII and connected live with GM TAC and my truck has not revved to 3500RPM but has coughed and fluttered upon starting but it recovers immediately.

Denny NWO
Denny NWO

My truck went to the dealership on Tuesday and GM gave me a rental to drive for the week while the tech took my truck home. It started normal the first few days but acted up Friday morning when he sta

SPASierra
SPASierra

Right, but even drive by wire TPS sensors are essentially a potentiometer that sends a voltage based on position of the throttle plate.   None of this is likely to be the cause of his issue, but the

Posted Images

Denny NWO Enthusiast

Denny NWO

Posted
  • Author
Posted

I showed the video to the mechanic at the dealership, its going in today.

Denny NWO Enthusiast

Denny NWO

Posted
  • Author
Posted (edited)

Here is the dealership technicians report: Nov 25 - Scan, no ECM codes stored and no bulletins apply. Codes U0140, U0131, U0151, U0102 and U0146 are set history in the BSCM which is related to bulletin 20-NA-155. A new BSCM cal is available to correct condition. Called TAC, no help. Removed the induction pipe at the throttle body, no sign of moisture or anything that would affect the throttle blade. The accelerator pedal is free of obstacles and does not appear to have anything that could hold it down. Parked truck outside over night. Next morning, Nov 26 - install the scan tool, monitor the induction data list and start. The engine RM flared up to 1850 then quickly down o a normal cold idle. The impression I got was an engine start with an incorrect idle learn. Found the idle compensation at 67% which seems high for a vehicle with 12K mileage. Inspect throttle body, completely clean. Correction: No repair possible today and no problem was found. I did install the latest BSCM cal, prog code 28YN51521209 for customer satisfaction and just in case it's related. Wipe down throttle body and perform an idle compensation relearn. Run and clear codes. The engine started without the flair this time. Customer to retry.

 

I will give it some time and see if it happens again and post if it happens again....or not.

Edited by Denny NWO
Denny NWO Enthusiast

Denny NWO

Posted
  • Author
Posted
On 11/26/2020 at 9:03 AM, mafd2 said:

Can you post the video on youtube and add the link here?

 

mafd2 Senior Enthusiast

mafd2

Posted
Posted

Wow!  Unbelievable... As said above it's like a runaway Detroit diesel from years back. I hope it gets figured out. Keep us updated and thanks for posting the video.

  • Like 1
Rob Mugs Enthusiast

Rob Mugs

Posted
Posted
11 hours ago, mafd2 said:

Wow!  Unbelievable... As said above it's like a runaway Detroit diesel from years back. I hope it gets figured out. Keep us updated and thanks for posting the video.

Been around one or two... even had  a deuce n a half that had been messed with run away on me

 

For those that haven't seen what happens

 

Denny NWO Enthusiast

Denny NWO

Posted
  • Author
Posted (edited)

I went to work today and after 10 hours of sitting outside in 20F cold, it started and fluttered and flared up to about 2000 RPM for 2 seconds then ack to idle and bounced up and down a bit. I never took my foot off the brake and did not touch the throttle. Video is noisy at the end as an aircraft was flying over on approach to the airport and I shut the drivers door. Guess the BSCM update didn't do much.

 

 

 

Edited by Denny NWO
kodiakdenali Enthusiast

kodiakdenali

Posted
Posted

Subscribing because mine just did something strange to me today, not what yours is doing though, but right after startup during the gauge sweep it sounded like it reved up to 1500-2000 or so, then right back to idle. it wasn't cold though, maybe 5c, in the garage. it was the second start but still cold. I was just moving it around to put the winter tires on it, a couple months too late! I'm not going to worry about it unless it happens again, but I'd like to hear what your final resolution was.

 

speaking of all of this, not that this situation seems likely to cause a runaway, but does anyone know how to do an emergency shutdown on this truck? this is something that I think keyless start systems need to get standardized on. I had a Ford once where you could do an emergency shutdown by holding the button for about a second. annoyingly it would only restart in park, it would not restart in neutral. I have had 2 FCA cars which as far as I can tell have no way to do an emergency shutdown at all, which is honestly rather scary. What would you do if you had a sudden coolant leak? or an loss of oil pressure? or a fuel line comes loose and you've got flames shooting out from under the hood...and the only way to stop the fuel pump from pouring fuel onto the fire is to get from your 85mph interstate speed to a complete stop to get the transmission in park before it will allow you to shut off the engine? especially with vehicles that have EPAS now (electric power assisted steering) and knowing that the vacuum in the brake booster will still give you one or two brake applications with power assist before you turn out of boost, it would seem that being able to shut down the fuel supply from the fireball under your hood is way more important for your safety than preventing engine from being able to turn off while in motion.

Denny NWO Enthusiast

Denny NWO

Posted
  • Author
Posted

It did a slight flare on the post from Sunday but on Monday, it went to 3500RPM for almost 8 seconds. Tuesday it started normal and Wednesday (tonight) it sputtered on start up and only slightly flared up. Every time this happens, it has been sitting outside for 8-10 hours after finishing work in temperatures just below freezing. It never does it in the morning at home parked in my heated garage. Here is Monday's start up. I have my foot on the brake the entire time and lift it at the end. It going back to the dealership tomorrow.

 

Denny NWO Enthusiast

Denny NWO

Posted
  • Author
Posted
On 11/30/2020 at 2:32 PM, kodiakdenali said:

Subscribing because mine just did something strange to me today, not what yours is doing though, but right after startup during the gauge sweep it sounded like it reved up to 1500-2000 or so, then right back to idle. it wasn't cold though, maybe 5c, in the garage. it was the second start but still cold. I was just moving it around to put the winter tires on it, a couple months too late! I'm not going to worry about it unless it happens again, but I'd like to hear what your final resolution was.

 

speaking of all of this, not that this situation seems likely to cause a runaway, but does anyone know how to do an emergency shutdown on this truck? this is something that I think keyless start systems need to get standardized on. I had a Ford once where you could do an emergency shutdown by holding the button for about a second. annoyingly it would only restart in park, it would not restart in neutral. I have had 2 FCA cars which as far as I can tell have no way to do an emergency shutdown at all, which is honestly rather scary. What would you do if you had a sudden coolant leak? or an loss of oil pressure? or a fuel line comes loose and you've got flames shooting out from under the hood...and the only way to stop the fuel pump from pouring fuel onto the fire is to get from your 85mph interstate speed to a complete stop to get the transmission in park before it will allow you to shut off the engine? especially with vehicles that have EPAS now (electric power assisted steering) and knowing that the vacuum in the brake booster will still give you one or two brake applications with power assist before you turn out of boost, it would seem that being able to shut down the fuel supply from the fireball under your hood is way more important for your safety than preventing engine from being able to turn off while in motion.

The Start/Stop button will shut the engine down. One time when the RPM took off to park redline (3500RPM), I just hit the start/stop button and it shut down immediately. I waited a few seconds and hit the start button and the engine started normally.

  • 2 weeks later...
Denny NWO Enthusiast

Denny NWO

Posted
  • Author
Posted (edited)

So it went to the dealer a second time and they flashed a new BSCM calibration and it started fine until yesterday and it did its random start and redline. Tonight it fired and stalled then the starter cranked for 7 more seconds and it fired and redlined and held until i kicked the throttle pedal. It's going back to the dealer for a third time and they will keep it until they figure out the problem.

 

2019 AT4 Cold Start High RPM after long crank.mov

Edited by Denny NWO

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.4k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,760
    Total Members
    8,960
    Most Online
    MASONV88888888
    Newest Member
    MASONV88888888
    Joined

  • Who's Online   3 Members, 0 Anonymous, 1,563 Guests (See full list)

  • Latest Articles

  • Posts

    • MASONV88888888
      Another 6.2L engine failure!

      By MASONV88888888 · Posted

      My 2025 Silverado 1500 had to receive a brand-new engine (long block) under warranty last month at only around 16,500 miles. Before the replacement, the truck repeatedly displayed "Engine Oil Level Low" warnings, even though the Oil Life Monitor still showed around 50% remaining after about 6,000 miles since my last oil change. After seeing the warning several times, I checked the dipstick with the engine cold, and the oil level was completely normal. The next day, the message escalated to "Add Engine Oil." At first, I assumed it was just a faulty oil level sensor, so I brought the truck to the dealership. After inspecting the engine, they found internal cylinder wall scoring and ultimately replaced the entire long block under warranty. Before this happened, I was planning to install a 4-inch lift and suspension upgrade on my truck. After needing a new engine at just 16,500 miles, I honestly don't see the point anymore. I also contacted GM to ask whether my vehicle qualified for a buyback, but I was informed that it does not at this time. Anyway, this experience has left me with serious concerns about the long-term reliability of this engine. I sincerely hope NHTSA expands the current investigation or recall to include 2025 model and performs a thorough inspection of affected vehicles. My biggest concern is that these engines may fail shortly after the powertrain warranty expires. If GM truly stands behind this engine, then at the very least, please consider extending the powertrain warranty to 10 years for affected owners. That would go a long way toward restoring customer confidence.
    • Grumpy Bear
      OCI, not when but why?

      By Grumpy Bear · Posted

      Without exception but then I'm the odd duck, right? I know what goes into that test, how it is calculated and thus how to beat it. But EPA values are often not beaten by the general public and the government has in past years adjusted the means and methods to come to those values to more closely approximate "Joe Average".    The only real trick to beating that EPA average is don't drive like "Joe Average".    It's the same method you used to profit from "Economic Migration" and in doing so beat the 'stats'. But you, like me, are not "Joe Average".     The thing you don't seem to grasp is this "Purchasing Power Index" isn't forward looking. It doesn't predict what it going to be but looks backward and states what it was. They are not telling us what the THINK, they are telling us what they MEASURED. Example:    Wife says "I'm going to lose 40 pounds by Christmas". May she does, maybe she doesn't but the doctors office who weighed her when she made that statement and again at Christmas only REPORTS what the RESULT was. You and I can banter about what was possible and what aunt Tilly did till the cows come home but the result is the result. Arguing otherwise is.....irrational. That's all I'm saying. This isn't about:      What you are calling a 'Statistic' is a RESULT not a CALCUATION and as a result the RULE. Like gravity as a rule, it can not be broken. 
    • MASONV88888888
      Rattle in the rear!

      By MASONV88888888 · Posted

      Just wanted to say thank you for posting this. Years later, your thread is still helping Silverado owners.   I bought my 2025 Silverado 1500 in January 2025, and I've had what feels like the exact same rattle since day one. After reading your findings, I believe my truck has the same issue with the cable carrier contacting the rear sliding window. To be honest, I had pretty much given up on pursuing the issue. It wasn't until I recently drove another brand's pickup that I realized just how quiet their cabin was—and how noisy mine has been all along. On my truck, the rattle happens on almost any paved road, gets even worse on rougher pavement, and I can even hear it during braking and acceleration.   I actually referenced your thread when submitting my case to GM, hoping they'll recognize this as a recurring issue instead of treating it as an isolated incident. The reason I reached out to GM first is because my dealership told me they would need to keep the truck for at least two days just to diagnose the problem. I was concerned that even after two days, they still might not be able to identify the source of the rattle before giving the truck back to me. I had also asked a few dealerships about this issue during previous service visits, but none of them seemed to know what was causing it or had a solution. That's why I decided to contact GM directly first, hoping they might already have an official repair procedure or guidance for this issue.   I also hope GM eventually comes up with an official fix for this problem. I have a feeling there are many Silverado owners experiencing the same rattle, but most either choose to live with it or simply don't know what the cause is.   Really appreciate you taking the time to document your diagnosis. Your post is still making a difference years later.
    • Buckwild27
      Gas Prices

      By Buckwild27 · Posted

      I have 2 choices. 
    • Grumpy Bear
      Gas Prices

      By Grumpy Bear · Posted

      Do you have access to BP fuels? Some stations have Silver 91 E-0 priced the same as their 93 E-10.  There is a local Marathon with 90 alky free for $6 a gallon but I go down the road to BP for $5-ish. They also have a 100 E-0 but that stuff is $10 a pop. 

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...