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Engine Missfire

Buzz1

By Buzz1
in Troubleshooting & Recalls

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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. 

 

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