Jump to content

Engine Missfire

Buzz1

By Buzz1
in Troubleshooting & Recalls

 Share

Recommended Posts

Buzz1 Enthusiast

Buzz1

Posted
Posted (edited)

Hello,

 

I have a 2016 Silverado LTZ (8 Speed, 5.3) with around 110,500 miles currently.  Earlier, back in December (107,339 Miles) after the truck had sat for a couple of days, I was driving down the flat highway (Going around 72) and all the sudden I noticed a flashing check engine light. I pulled over and then the light turned steady. I called onstar and they informed me that it was a engine missfire, since the light was no longer flashing I continued to drive. Later the light turned itself off. Later on in the trip the check engine light started to flash and then turned solid. Again, I called Onstar and they told me it was a misfire. The light hen turned off the next day.  I also took a trip to auto zone after the light had turned off and got them to scan my truck and they gave me a more detailed answer. There was a pending code of P0305 for a misfire in cylinder 5.  The weather during that drive was clear but very cold, around freezing. The engine never fully warmed up. I thought it was just a random issue, or bad fuel until this evening. I was driving going around 40 miles per hour, (Engine fully warmed up, weather was around 42 degrees), and the check engine light came back on. I pulled over into a parking lock and pulled out my scanning tool and shut off the truck, I restarted the truck and the check engine light was gone. I checked the code scanner and all that was there was a pending code of p0305 for a misfire. I cleared the codes and nothing has come up since.  All three times that this has happened, I felt no misfire or loss of power from the engine. The code has disappeared every single time. My question is, is this something I should worry about? Should I take this to a mechanic even though nothing seems to be running wrong with the truck? I will also attach a video of the truck idling. 

truckrunningaudio.m4a

Edited by Buzz1
CamGTP Senior Enthusiast

CamGTP

Posted
Posted (edited)

Yes, it's still a problem that you should be worried about. The light wouldn't be coming on if this wasn't a problem.

 

Could be as simple has a failing spark plug or plug wire. Other things could be a fuel injector issue.

Edited by CamGTP
Buzz1 Enthusiast

Buzz1

Posted
  • Author
Posted
11 minutes ago, CamGTP said:

Yes, it's still a problem that you should be worried about. The light wouldn't be coming on if this wasn't a problem.

 

Could be as simple has a failing spark plug or plug wire. Other things could be a fuel injector issue.

Would it be possible for it to be one of those options if there is no detectable difference in the engine running or driving when the misfiring is occurring / make the issue intermittent, or because of that is it more likely a bad sensor? If so, what sensors would go bad and cause a false flag for a misfire. 

ftwhite Enthusiast

ftwhite

Posted
Posted (edited)

If you didn't feel the misfires, it's much more likely a bad crank position sensor. That's what the ecu uses to calculate a misfire. It expects the crank to accelerate and decelerate in an exact pattern based on cylinders firing. When it gets this wrong repeatedly, it reports the misfire. It's not hard or expensive to replace, so start there (imo).

Edited by ftwhite
Lsgun1 Enthusiast

Lsgun1

Posted
Posted

Have you changed plugs and wires ever? Start simple don't go replacing sensors, the computer picks up a misfire a lot faster then you do.

newdude Senior Enthusiast

newdude

Posted
Posted
On 3/15/2021 at 11:43 PM, Buzz1 said:

Hello,

 

I have a 2016 Silverado LTZ (8 Speed, 5.3) with around 110,500 miles currently.  Earlier, back in December (107,339 Miles) after the truck had sat for a couple of days, I was driving down the flat highway (Going around 72) and all the sudden I noticed a flashing check engine light. I pulled over and then the light turned steady. I called onstar and they informed me that it was a engine missfire, since the light was no longer flashing I continued to drive. 

 

There was a pending code of P0305 for a misfire in cylinder 5.  The weather during that drive was clear but very cold, around freezing. The engine never fully warmed up. I thought it was just a random issue, or bad fuel until this evening. I was driving going around 40 miles per hour, (Engine fully warmed up, weather was around 42 degrees), and the check engine light came back on. 

truckrunningaudio.m4a 310.79 kB · 3 downloads

 

 

Ever had any fuel injectors replaced yet?  May or may not set a P050D as well.  

  • Like 1
Logan Lanfear Enthusiast

Logan Lanfear

Posted
Posted

Change all the plugs, after 115k its probably time. Go with OEM or something quality. If you don't know how to read plugs then post a picture of all 8 on here and we can tell you how they look. While you're there, changing the wires isn't a bad idea either. 

Its a good time for a tune up. If it doesn't fix the issue then you can look deeper into injectors or CPS. Its a good time to change the plugs anyway. 

Buzz1 Enthusiast

Buzz1

Posted
  • Author
Posted
On 3/17/2021 at 11:23 AM, Logan Lanfear said:

Change all the plugs, after 115k its probably time. Go with OEM or something quality. If you don't know how to read plugs then post a picture of all 8 on here and we can tell you how they look. While you're there, changing the wires isn't a bad idea either. 

Its a good time for a tune up. If it doesn't fix the issue then you can look deeper into injectors or CPS. Its a good time to change the plugs anyway. 

 

I just had all the plugs and wires replaced by the dealer at around 103,000 miles. One of my good friends and I checked out the spark plug on the cylinder with the issue and it looks fine, but it was a little bit looser than the other plugs. We tighten it put it back in, and switched its wire with another one from a different cylinder, we are going to see what happens then. 

 

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

  • Latest Articles

  • Posts

    • Chuck FB
      Correct way to service 2024 l8t allison trans?

      By Chuck FB · Posted

      If you have actually done it, there must be some secret tool or method of accessing the hidden bolt head that both manifold connections have. Two of the three bolt heads are staring at you in the face from below but the third one is covered by shielding and as far as I know only accessed by removing part of the fender well lining to gain access to it and even then its awful to access or from what I had seen of someone fighting with it on a video.    There is a reason why even mechanics that deal with the awkward or risky business of undoing the exhaust at the manifolds have done the same method others are doing with these L8T by flexing the exhaust if need be or just able to slip the pan out as I did without needing to touch hardware or pry on the exhaust. By rights the two seals should be replace when those joints are cracked loose as well.     
    • Chuck FB
      Correct way to service 2024 l8t allison trans?

      By Chuck FB · Posted

      Actually it was a lot more controlled then I thought it might be and that isn't actually when I spilled some oil. I had thought prior of rounding up a couple of longer bolts with the same thread to swap out for a couple of the front edge pan bolts and then leaving one bolt left in the back but loosened off and then using a suction device to remove most of the fluid, that certainly would have worked and while I do have a couple of different devices I could have used to suck the fluid, now having done the job once I wouldn't even bother. I had thought of buying one of those pressurized vessels to suck or new fluid in and would if I was doing a job like this on a few vehicles but with one vehicle I just didn't bother and I have pail pumps as well I could have used assuming the hose end would fit into that less than roomy space but being such a thin fluid it pumped well with a quart type pump and just kept the hose into the trans and kept swapping containers and repeat.    What I would change to the method I did though was first jack up just the rear of the truck to put on jack stands to allow more oil to come out of the check plug on the front of the pan ( and as I did, I made sure to put that drain plug back in finger tight ) then follow through by putting the front on jack stands. Also that I would have used a larger sized drain pan in the sense of covering an area wider/longer beyond the transmission but I didn't have one and saw someone else on a youtube video using a masonry mud mixing tub and bought one at a hardware store to use in the future. The main oopsy  I did and why I spilled some oil was all my fault as I neglected to follow my own plan, I should have let down the pan as I did to drain out the front of it as much as would come out but then scooped out the remainder of the oil with the Dixie cup I had sitting there just for that purpose as by that point there is enough room to reach right into the front of the pan and just bail it out basically. 
    • No F-bdy Bs
      Correct way to service 2024 l8t allison trans?

      By No F-bdy Bs · Posted

      Pretty easy to just remove/drop the exhaust behind the manifolds. They're in no way hard to get to. Maybe 5min of work, and you get the opportunity to put some anti-sieze on them in case anything ever comes up, you eliminated the risk of snapping a stud. 
    • No F-bdy Bs
      first oil change - 2026 2500HD gas

      By No F-bdy Bs · Posted

      I let the dealer do every other oil change simply so they can rotate the tires, which is a pita at home. 
    • bruceb58
      Correct way to service 2024 l8t allison trans?

      By bruceb58 · Posted

      I addition, I won't have a pan full of fluid sloshing around to get all over the place.   I am putting on the Dorman pan with the drain plug. It looks like it is around the same height. I have one of these guys to make life a lot easier.   https://www.amazon.com/dp/B09CDXJCCT?ref=fed_asin_title&th=1      

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...