Jump to content

2015 diagnostic mystery

Potius
 Share

Recommended Posts

Potius Enthusiast

Potius

Posted
Posted

Hello everyone so I’m praying someone has some advice for me. So I have a 2015 Silverado LT 1500 5.3L. About a month ago started running really rough down shifting rough and MIL is on. Scanned it and got P0308, P219B, and P050D. Checked live misfire data on scanner and cyl 8 had over 25k misfires. Next step I took was swapped spark plug, coil and wire from 8 to 4 cleared codes and started her up. No difference and misfire didn’t move cylinders. Used scanner to perform an injector balance test and both fuel rails have good pressure and all injectors tested within acceptable variance. Next pulled valve cover off and made sure all rockers were moving and rocking and they all looked great and in sync so ruled out stuck lifter. Did a compression test and compression is there at 150. So today cleared codes(due to coil pack change etc had some stored) and started it up. Now only codes I have are P0300 and U0401:00. Cylinder 8 is misfiring a lot and cylinder 7 seems to be missing more and more. Just for sh*** and giggles I plugged in the range afm disabler from my Tahoe and the truck seems to have smoothed out a lot and it’s barely rough but drives weird so I unplugged it after checking. So long story short I am completely stumped as to what could be causing my issues and any advice or help would be greatly appreciated.

rav3 Senior Enthusiast

rav3

Posted
Posted

How many miles?  Any modifications? Any tune ups or engine maintenance? 

Potius Enthusiast

Potius

Posted
  • Author
Posted

190k miles with no mods. Owned it since 105k maintained since then meticulously. No recent tune ups in last 30k other than fluid changes. Oh I did put a Rough Country cold air intake on it. As to the thread going to start reading it now and thank you for the link

Potius Enthusiast

Potius

Posted
  • Author
Posted

Thank you for that link asilverblazer. Definitely helped me zero down some things. So went back to testing concentrating on the fuel aspect. My pressures seemed within range 45-60psi low side and around 700’s high side at idle. Did the injector balance test/correction and I believe all injectors tested within acceptable variance. I attached the injector balance numbers. Here’s the thing though when doing the test there was a noticeable drop in rpm when I did each injector which is suppose to happen. However when I did injector 7 the feeling wasn’t as strong and when I did injector 8 you barely felt any hiccup at all. Injector 8 is the one with 45k misfires and injector 7 has 950.

Now with me ruling out most everything else and not having any lifter noise compression or spark issue etc would it be a safe bet to buy the 2 injectors for 7 and 8 and pick up a new hpfp. I figure it needs the injectors and with almost having 200k the hpfp should be around end of life so would be preventative if nothing else.

  • Like 1
asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted

A couple things...

1. At the most recent oil change did the old oil smell of gasoline? Sometimes the high pressure pump leaks to the crankcase. I don't recall specs for fuel rail pressure but 700 seems low.

2. I would pursue injectors or fuel pump separately. You've done the injector balance test and the results do not indicate an injector issue. You can run the test as many times as needed to confirm that result. If you choose to replace any injectors do so one at a time with a genuine GM part. I would try the high pressure fuel pump first if the pressure is indeed low. I would not replace the pump and injectors at the same time, too many variables start getting introduced. 

Potius Enthusiast

Potius

Posted
  • Author
Posted

Due to the fuel lines being 1 time use I’m going to do the 1 injector on cylinder 8 due to getting almost no change in rpm’s during injector test and the fuel pump. Wish me luck parts should be here in a few days

Potius Enthusiast

Potius

Posted
  • Author
Posted

On a side note rock auto tells me the correct injectors are the nominal flow part # 12710481. It’s the only gm genuine injector listed so I assume it’s right lol

asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted (edited)

Proceed with caution, there are counterfeit parts... the new one may end up being worse than the old one. 

 

I'm not being critical of your course of action, just warning you not to assume that putting a new injector in (or any part for that matter) rules it out as the culprit of the problem.

 

Be careful with the intake gaskets too. They are supposed to be replaced when you pull the manifold.

Edited by asilverblazer
  • 2 months later...
Potius Enthusiast

Potius

Posted
  • Author
Posted

Ok sorry for the time since last update. Finally got parts/time so went to remove cylinder 8 injector and course rail was stuck so bent that coming out. Ended up just putting a new passenger side fuel rail and 4 new injectors in it. Changed intake gaskets just to be sure and put everything back together. Double checked everything and started her back up. Not a single change. Everything is exactly as it was before with cylinder 8 misfiring. At this point I’m about to change the HPFP mainly due to being stumped what else it could. A quick recap:

spark plugs checked and verified there is spark

coil packs checked/ moved with no change

spark plug wires checked an spark verified

compression test good on all cylinders

took valve cover off and all rockers good and doesn’t look like stuck lifter at all

checked for vacuum leaks and smoke tested 

 

Honestly if it’s not the HPFP then it must be electrical and I’m way out of my league 

 

asilverblazer Senior Enthusiast

asilverblazer

Posted
Posted (edited)
21 hours ago, Potius said:

Ok sorry for the time since last update. Finally got parts/time so went to remove cylinder 8 injector and course rail was stuck so bent that coming out. Ended up just putting a new passenger side fuel rail and 4 new injectors in it. Changed intake gaskets just to be sure and put everything back together. Double checked everything and started her back up. Not a single change. Everything is exactly as it was before with cylinder 8 misfiring. At this point I’m about to change the HPFP mainly due to being stumped what else it could. A quick recap:

spark plugs checked and verified there is spark

coil packs checked/ moved with no change

spark plug wires checked an spark verified

compression test good on all cylinders

took valve cover off and all rockers good and doesn’t look like stuck lifter at all

checked for vacuum leaks and smoke tested 

 

Honestly if it’s not the HPFP then it must be electrical and I’m way out of my league 

 

I don't think a HPFP would only cause problems on a specific cylinder. 

 

Did you swap plug and plug wires from a good non missing cylinder?

 

Good ignition, good fuel... inspect everything from the cam shaft to the valves.

 

Take a look here:

 

Edited by asilverblazer
Potius Enthusiast

Potius

Posted
  • Author
Posted

I swapped plugs and wires with 2 other cylinders to be sure and no change as well as checked for spark and it has it. I’ve literally checked everything 

silveradosid Senior Enthusiast

silveradosid

Posted
Posted

i would hook a vacuum gauge to the intake manifold, should be 18 to 20 inch vacuum. the needle on the gauge should stay still. if the gauge is fluctuating then you have a valve problem. does it take more cranking on cyl 8 to get good compression.

Potius Enthusiast

Potius

Posted
  • Author
Posted

Where do you connect a vacuum gauge on this engine? It doesn’t seem to have vacuum lines and I thought the brake booster line didn’t work for a gauge cause it goes directly to the vacuum pump and not into the engine

Potius Enthusiast

Potius

Posted
  • Author
Posted

Ok so I decided to not buy another part until I actually found something damaged or wrong. Unfortunately that only left valves lifter and cams to check. So had a fun day today in the cold(northern Maine here) and here is what I found so far:

valve pic (cylinder 8 is the black valves)

IMG_0523.jpeg

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
      Gas fill door

      By newdude · Posted

      Common failure.  You need to replace the fuel door housing.   The painted cover transfers over to the new housing.  To remove the old one there is 4 spots where you poke the plastic to release it.  
    • 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

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...