Jump to content

2014 GMC Sierra misfire

svan78

By svan78
in Troubleshooting & Recalls

 Share

Recommended Posts

svan78 Enthusiast

svan78

Posted
Posted

i could use some advice....

 

I bought a 2014 GMC Sierra crew cab z71 4x4 and my check engine light flashes so i take it to the dealer. Truck has 5k miles on it. Dealer says it is a misfire on cylinder 8. They tell me it had a loose clip on the spark plug.

 

500 miles later the check engine light flashes again. Go to the dealer again its a misfire on cylinder 8. They replace the plug and the wire. Said it was a bad plug.

 

500 miles later the light flashes again. I call the dealer and they tell me they will have to teardown the enging to cylinder 8 to see what the problem is.

 

Does this sound right for an engine with less than 7k miles to need a teardown to cylinder 8? What does that all consist of anyways i ask? The serive guy never gave me a straight answer and wouldnt tell me what the compression was on that cylinder.

 

I dont like the sounds of teardown a new engine and asked for that coil pack to be replaced and was told no.

 

Anyways anyone had any problems similar to this and could offer some adive or tell me what a teardown to cylinder 8 consist of?

 

Thanks

LongrangeLauber Senior Enthusiast

LongrangeLauber

Posted
Posted

Well its pretty time consuming to pull a head.

 

If they won't even try a new coil pack before pulling the head then there is something wrong with them. Try the easy things first. Go to a different dealer and tell em the entire story and see what they can do for you. I know I would have started with the plug and wire, then moved onto coil pack, then check the wiring harness that runs all the way to that coil pack. If all is good, then check the injector flow rate. I couldn't imagine needing to pull a head or even more for a misfire

svan78 Enthusiast

svan78

Posted
  • Author
Posted

My point exactly...why pull the head before you tried the coil pack? I was hoping someone with a similar problem could tell what fixed their 2014. but thanks for the reply

  • Like 1
pm26 Senior Enthusiast

pm26

Posted
Posted

A misfire could be the result of an ignition problem or fuel problem (malfunctioning fuel injector. A dealer should have the ability to diagnose the system to see if it is fuel related. if not, then replacing the suspect ignition component(s) is in order. This is ridiculous.

pm26 Senior Enthusiast

pm26

Posted
Posted (edited)

I am speaking from experience. I had a misfire code on my Mazda 626 some time ago. Te local dealer tech first checked the ignition, even swapped the spark plugs, which did not help. The car has a single ignition coil with 6 ports, so this was not a suspect. Then the tech connected his breakout box to the engine ECM (computer unit) and it showed him clearly which injector was misfiring. Therefore it seems to me that GM should have a similar procedure to diagnose cylinder misfire problems. In case of individual coils per plug, they should also swap out the coil from another cylinder to eliminate/identify if this is an ignition related issue.

 

BTW, it took 325k miles of driving for this car's engine to throw its first misfire code. And even a very good experienced tech could not determine at a glance whether the problem was ignition or fuel system related without proper test procedure.

Edited by pm26
redwngr Senior Enthusiast

redwngr

Posted
Posted (edited)

Connector with poor connection in harness to #8 injector?

 

Let'em do their thing. that's what warranty is for (but I'm betting service advisor is not correct about the next step in the 'diagnostic list')

Edited by redwngr
DeePa Enthusiast

DeePa

Posted
Posted

I had a cyl 6 misfire...they replaced the injector. It had 5800 miles and no issues since. Fuel pressure was low on that cylinder.

pm26 Senior Enthusiast

pm26

Posted
Posted

Connector with poor connection in harness to #8 injector?

 

Let'em do their thing. that's what warranty is for (but I'm betting service advisor is not correct about the next step in the 'diagnostic list')

You mean the "NORMAL" step?

Silverado915 Enthusiast

Silverado915

Posted
Posted

Why not swap #8 coil to #6 cylinder and see if the misfire follows? If it does you have a bad coil. If it doesn't you probably have a bad injector. I'm leaning towards the injector personally though.

  • 6 years later...
Gmc sierra guy New Member

Gmc sierra guy

Posted
Posted

I have a 2014 gmc sierra 5.3 the code reads a misfire on cylinder 7 which is a cylinder that kicks it into 4 cylinder mode, before this when j start mh truck it sounds like a dry lifter until the oil gets to it and it quiets down! My buddy said it is most likely the lifter giving out! Does this sound accutate to anyone?

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

    • newdude
      Gasser Subforum Has Been Quiet - - So, Regenerative Braking and Using L10

      By newdude · Posted

      No such thing as regenerative braking on a pure ICE vehicle.     Regenerative braking is the re-capture of energy from electric motors and stores it in the battery pack.  So hybrids, PHEV and EVs have regenerative braking.     What you are seeing is the charging system changing modes is all.  Its likely entering charge mode for some sort of reason is all.  All of the charging modes will be listed below.   As for L10 vs D.  L10 turns off automatic grade braking.  L10 puts you in control of grade downshifts where in D it will automatically do it based on brake pedal position and other factors.  Otherwise L10 and D drive exactly the same aside from that one aspect.    Battery Sulfation Mode The BCM will enter this mode when the interpreted Generator output voltage is less than 13.2 V for 45 minutes. When this condition exists the BCM will enter Charge Mode for 2–3 minutes. The BCM will then determine which mode to enter depending on voltage requirements.   Charge Mode The BCM will enter Charge Mode when ever one of the following conditions are met:   Windshield wipers are ON for more than 3 s. Climate Control Voltage Boost Mode Request is true, as sensed by the HVAC control module via serial data. High speed cooling fan, rear defogger, and HVAC high speed blower operation can cause the BCM to enter the Charge Mode. The estimated battery temperature is less than 0°C (32°F). Battery State of Charge is less than 80%. Vehicle speed is greater than 145 km/h (90 mph) A current sensor malfunction exists. System voltage is determined to be below 12.56 V When any one of these conditions is met, the system will set targeted generator output voltage to a charging voltage between 13.9–15.5 V, depending on the battery state of charge and estimated battery temperature.   Fuel Economy Mode The BCM will enter Fuel Economy Mode when the estimated battery temperature is at least 0°C (32°F) but less than or equal to 80°C (176°F), the calculated battery current is less than 15 A and greater than −8 A, and the battery state-of-charge is greater than or equal to 80%. Its targeted generator output voltage is the open circuit voltage of the battery and can be between 12.5–13.1 V. When fuel economy mode is active, the generator is not charging, only maintaining open circuit battery voltage. The BCM will exit this mode and enter Charge Mode when any of the conditions described above are present.   Headlamp Mode The BCM will enter Headlamp Mode when ever the head lamps are ON (high or low beams). Voltage will be regulated between 13.9–14.5 V.   Start Up Mode When the engine is started the BCM sets a targeted generator output voltage of 14.5 V for 30 s.   Tow/Haul Mode (if applicable) Pressing the Tow/Haul Mode button located on the center stack, the vehicle system voltage is raised and the remote (non-vehicle) battery will be charged. Having the headlamps on will raise the system voltage and if the Tow/Haul button is applied it will not serve any purpose. The voltage is regulated between 13.9-14.5 V.      
    • jaszr2
      Active Grille Delete

      By jaszr2 · Posted

      Hello from Australia Just sharing that there is now a way to delete the active shutters entirely with just a plug in module. Opens up tons of room to light bars etc.
    • jake111
      Gasser Subforum Has Been Quiet - - So, Regenerative Braking and Using L10

      By jake111 · Posted

      I have an observation and a question... 1) I watch the voltage closely because I have had to dial in the cut-in/cut-out voltages of the battery separator to my camper.  The "smart" charging drives me nuts.  Anyway, I noticed that when coasting for a while, and especially if lightly using the brakes (though not necessary), the voltage goes up from mid/high-13 volts to mid/high-14 volts.  Then it drops back down after stopping or going again.  Consistently!   The only explanation I can come up with is REGENERATIVE BRAKING!  Well, maybe that's a little bit of an exaggeration, but it's certainly free extra battery charging.   2) Driving on mountain roads I will use L and vary the max gear.  Things straighten out and I end up in L10.  Sometimes I leave it there for a while.  Is there any difference between L10 and D?   
    • devonthegreat
      anyone interested in a 2002 Chevy Silverado 4x4 parts truck NYC

      By devonthegreat · Posted

      **SOLD** Please end or delete post. thank you
    • PBNB
      Tire pressure for 37s

      By PBNB · Posted

      Do you think this width might affect the chalk test with a higher pressure closer to 65psi? I think lowering the pressure makes sense to get the tread to lay flatter

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...