Alright guys. I recently bought a 2016 Silverado 4x4 w/ 75k miles. When i first got it the idle was a little rough but thought coil packs, plugs and wires would do the trick. When i would remote start my truck i would get the misfire code and when driving and slowing down my transmission seemed to downshift hard. Along with a loss of power i reset the code and it seems to run better but still feel a rough idle. I changed the cylinder 5 plugs, wire, and coil got a fresh oil change and cant seem to the find the problem. Also sometimes my truck doesn't go into v4 when it used to. I went to a relatives shop and he hooked it up to a reader and it said everything I changed was doing good but i had 50 misfires in like 1 min just on that cylinder 5. Is there anybody out there that knows what the issue could be I'm lost!
2016 5.3 cylinder 5 misfire
- Thread starter buterama
- Start date
A Big Holiday 'Welcome to GMT Nation...'
Get a Bright Flashlight and scan the top of the Engine for any signs of Rodents Chewing on the EFI Wiring Harnessing and all of the Plastic Weather-Pack Connectors. Start with the #5 EFI and keep looking things over for the full length of the Harness.
Be fastidious and check for signs of their habitation; (Destroyed Hood Insulation, Pine Needles, Dried Urine & Feces). Check under the TB Cover for signs of Nesting, and Fur and also the look into the corners of the Engine Nacelle for the same.
Beware that the Common Field Deer Mouse is famously infected with the Hanta Virus transmitted by breathing in dried particles of this Junk... so use an N-95 Mask and Nitrile Gloves when vacuuming this Crap out of the area or seal up everything in Zip-Lock Bags and dispose of this Threat.
Avoid using Crimp-On Wire Connectors in favor of Solder and Sealing Heat Shrink Insulators if such repairs are in order. If needed, replacement Connectors with Pigtails are available from Amazon and also eBay as Used articles as well.
If you are fortunate enough to have and use either an inexpensive Hantek Model #1008C or a PICO-Scope Model # 2204A Oscilloscope to Diagnose the performance of your EFIs... THIS is what a Known, Good EFI Wave Form looks like as a Baseline for Comparison to your own.
Observe that Small Bump in the secondary portion of the Wave Form as it demonstrates the precise time that a properly functioning EFI Pintle Valve closes off the Fuel Spray. If THAT artifact is missing, or if the lead in Rectangular Primary Current Ramp is neither symmetrical nor having its Primary Spike image appearing "Tall" then you should suspect that you have a Failing #5 EFI:
EDIT: Monday, September 2nd, 2024 @ 02:ish EST:
NOTE: Eric "O"s contributions are covered in the next Post added by @Mooseman.... and HE did these suggestions PRIOR to my Related Video Inclusion Edits below:
This information relates to the GM 5.3L Engine...These "Cylinder Leak Down Test" Procedures are so well covered... and the Value of seeing "Kit" ... a Pro Mechanic ... conducting a very detailed and Hands-On Demonstration of a Cylinder Leak Down Test.
It is well worth adding these "visual" instructions in here while "Kit" makes pointed observations about the differences between Shops that are "Parts Changers" versus Shops that understand the value of Proper Diagnostic Procedures being shown in this Video:
And along the same lines...from Eric "O" at SMA (South Main Auto) up in Avoca, NY:
Get a Bright Flashlight and scan the top of the Engine for any signs of Rodents Chewing on the EFI Wiring Harnessing and all of the Plastic Weather-Pack Connectors. Start with the #5 EFI and keep looking things over for the full length of the Harness.
Be fastidious and check for signs of their habitation; (Destroyed Hood Insulation, Pine Needles, Dried Urine & Feces). Check under the TB Cover for signs of Nesting, and Fur and also the look into the corners of the Engine Nacelle for the same.
Beware that the Common Field Deer Mouse is famously infected with the Hanta Virus transmitted by breathing in dried particles of this Junk... so use an N-95 Mask and Nitrile Gloves when vacuuming this Crap out of the area or seal up everything in Zip-Lock Bags and dispose of this Threat.
Avoid using Crimp-On Wire Connectors in favor of Solder and Sealing Heat Shrink Insulators if such repairs are in order. If needed, replacement Connectors with Pigtails are available from Amazon and also eBay as Used articles as well.
If you are fortunate enough to have and use either an inexpensive Hantek Model #1008C or a PICO-Scope Model # 2204A Oscilloscope to Diagnose the performance of your EFIs... THIS is what a Known, Good EFI Wave Form looks like as a Baseline for Comparison to your own.
Observe that Small Bump in the secondary portion of the Wave Form as it demonstrates the precise time that a properly functioning EFI Pintle Valve closes off the Fuel Spray. If THAT artifact is missing, or if the lead in Rectangular Primary Current Ramp is neither symmetrical nor having its Primary Spike image appearing "Tall" then you should suspect that you have a Failing #5 EFI:
EDIT: Monday, September 2nd, 2024 @ 02:ish EST:
NOTE: Eric "O"s contributions are covered in the next Post added by @Mooseman.... and HE did these suggestions PRIOR to my Related Video Inclusion Edits below:
This information relates to the GM 5.3L Engine...These "Cylinder Leak Down Test" Procedures are so well covered... and the Value of seeing "Kit" ... a Pro Mechanic ... conducting a very detailed and Hands-On Demonstration of a Cylinder Leak Down Test.
It is well worth adding these "visual" instructions in here while "Kit" makes pointed observations about the differences between Shops that are "Parts Changers" versus Shops that understand the value of Proper Diagnostic Procedures being shown in this Video:
And along the same lines...from Eric "O" at SMA (South Main Auto) up in Avoca, NY:
Last edited:
So it's not misfiring all the time? Is it doing it at idle or while driving? I had a similar issue with my 4.2 at idle only.
gmtnation.com
What I would check on your truck:
- compression test all cylinders, dry and wet
- fuel pressure
- injector balance test
- use a noid light to check the #5 coil is being fired correctly
- try a CASE (crank variation) relearn
Since it's cylinder 5 that's misfiring, I wouldn't suspect the AFM lifters since 5 is not one of those cylinders. It's probably not going into V4 because of the misfire.
What are your fuel trims like? Did you have just the one code for the misfiring cylinder (P0305)? What brand/type spark plugs did you use? Although the LS engines aren't as picky as the I6, I'd still go with ACDelco iridium plugs.
This is one of the newest engines we've seen here so there may be things we're not aware of. Hopefully we can get this figured out.
Very Slight Miss at Idle
Yesterday on the TB, at 117k km, saw the CEL come on and code came up for P0304. Fired up Torque and it was missing on cylinder #4 but only at idle or stopped at a light. It's not a big miss since I can't feel it at all and it's just a couple of misses per refresh cycle. While driving...
gmtnation.com
What I would check on your truck:
- compression test all cylinders, dry and wet
- fuel pressure
- injector balance test
- use a noid light to check the #5 coil is being fired correctly
- try a CASE (crank variation) relearn
Since it's cylinder 5 that's misfiring, I wouldn't suspect the AFM lifters since 5 is not one of those cylinders. It's probably not going into V4 because of the misfire.
What are your fuel trims like? Did you have just the one code for the misfiring cylinder (P0305)? What brand/type spark plugs did you use? Although the LS engines aren't as picky as the I6, I'd still go with ACDelco iridium plugs.
This is one of the newest engines we've seen here so there may be things we're not aware of. Hopefully we can get this figured out.
Yes i will try these this weekend! its only noticeable when idling and thats when it pops the CEL. Its just that p0305 code as well.So it's not misfiring all the time? Is it doing it at idle or while driving? I had a similar issue with my 4.2 at idle only.
Very Slight Miss at Idle
Yesterday on the TB, at 117k km, saw the CEL come on and code came up for P0304. Fired up Torque and it was missing on cylinder #4 but only at idle or stopped at a light. It's not a big miss since I can't feel it at all and it's just a couple of misses per refresh cycle. While driving...
What I would check on your truck:
- compression test all cylinders, dry and wet
- fuel pressure
- injector balance test
- use a noid light to check the #5 coil is being fired correctly
- try a CASE (crank variation) relearn
Since it's cylinder 5 that's misfiring, I wouldn't suspect the AFM lifters since 5 is not one of those cylinders. It's probably not going into V4 because of the misfire.
What are your fuel trims like? Did you have just the one code for the misfiring cylinder (P0305)? What brand/type spark plugs did you use? Although the LS engines aren't as picky as the I6, I'd still go with ACDelco iridium plugs.
This is one of the newest engines we've seen here so there may be things we're not aware of. Hopefully we can get this figured out.
Dudeman
Member
What did the relative with the scanner think? Any ticking noises? Not sure about 16's, but had a 17' with a bent pushrod and found that to be very common. With the pedal to the floor cranking, is there a good ru, ru, ru, ru ru, ru, ru, ru, ru sound with good cadence, or does one of the ru's sound more like a "wee"? I hope that was the correct spelling 
.
.He is a old school mechanic so not the best with new age computers lol. He said everything looked good and he was in shock as to why that didn’t fix it. There is a slight ticking noise and does increase with acceleration. As for the sound of the cadence I’ll have to check I haven’t noticed any issue with it starting up