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Thread: 2014 silverado misfire

  1. #1
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    2014 silverado misfire

    Had a solid tune in since April 2020. Just recently had a massive loss of power and multiple misfire and lean codes.
    Replaced coils, wires, plugs, maf sensor.
    Then found fuel in the vacuum lines.
    Still have same issue I think it's the fuel pressure regulator.
    Dealership says its my after market parts and tune. after demanding they replace the fuel pump assembly where the fuel pressure regulator is located it supposedly still has the same issue.

    I'm fresh out of ideas every mechanic I talk to says it's the fpr. That includes other dealerships.

    Thanks for any help provided.

  2. #2
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    Quote Originally Posted by lord4play79 View Post
    Had a solid tune in since April 2020. Just recently had a massive loss of power and multiple misfire and lean codes.
    Replaced coils, wires, plugs, maf sensor.
    Then found fuel in the vacuum lines.
    Still have same issue I think it's the fuel pressure regulator.
    Dealership says its my after market parts and tune. after demanding they replace the fuel pump assembly where the fuel pressure regulator is located it supposedly still has the same issue.

    I'm fresh out of ideas every mechanic I talk to says it's the fpr. That includes other dealerships.

    Thanks for any help provided.
    What 2014 Silverado has a vacuum referenced FPR?

  3. #3
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    Most of the ones I see with this issue needs a High Pressure Fuel Pump and injectors.

  4. #4
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    Check your fuel pressure on the low pressure side. Fuel in vacuum lines or PCV lines would be from a failed HPFP more than likely, and would set a P0172. Im assuming you have a P0171 and P0174? Id start with fuel pressure checks, then check the oil. if the HPFP failed, it will smell like straight gas, and likely be overfilled. less likely could be a failed 02 sensor, but Im doubting that. let us know what you find.

  5. #5
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    Just got it back from the dealership. They said all pressures are good and it's not the pumps. Still straight gas smell and the inside of the intake is wet with fuel. Hoping that it's working fuel out of the lines. Fuel pressure doesn't drop anymore. But it idles and runs even rougher then it did when I took it in.
    Fuel condensation in the lines coming from valve covers.

    While parked it revs up fine but once under load is when I have problems.

    Will keep you updated

  6. #6
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    Just noticed about a half inch of fuel in the oil... wasn't like that before I took it to the dealership

  7. #7
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    Quote Originally Posted by lord4play79 View Post
    Just noticed about a half inch of fuel in the oil... wasn't like that before I took it to the dealership
    you need a new High pressure fuel pump and the two high pressure fuel pipes to replace.. and youll be set.

  8. #8
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    Ok update... new hpfp installed same loss of power, bad mpg, backfiring. No check engine light but when I put a scanner on it it says p0101 maf low.. swapped it with brand new maf same problem. At idle it sounds great but touch the throttle and it spits and sputters but no cel...

  9. #9
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    Assume the oil was changed? Did you do the work or this dealership? Also assume when the hpfp was done that whomever pulled out and checked the lifter?
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

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  10. #10
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    I did the hpfp and did change the oil. I noticed no other issues. I'm already 4 grand deep and I'm running out of stuff to replace that might be causing the problem. I have no clue what's going on.

  11. #11
    Senior Tuner SultanHassanMasTuning's Avatar
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    can you post a log
    Follow @MASTUNING visit www.mastuned.com
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  12. #12
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    I will try to get a log posted soon.

  13. #13
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    Quote Originally Posted by lord4play79 View Post
    Ok update... new hpfp installed same loss of power, bad mpg, backfiring. No check engine light but when I put a scanner on it it says p0101 maf low.. swapped it with brand new maf same problem. At idle it sounds great but touch the throttle and it spits and sputters but no cel...

    Try checking your Throttle body compensation if you can on a scan tool, if its more than 90% try cleaning it. Also, if able to access data on scan tool, check to see is Throttle body position sensors 1 and 2 say "agree". Ive seen a few Throttle bodies go bad and mirror other issues, i.e. HPFP etc.

  14. #14
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    Quote Originally Posted by Estep40511 View Post
    Try checking your Throttle body compensation if you can on a scan tool, if its more than 90% try cleaning it. Also, if able to access data on scan tool, check to see is Throttle body position sensors 1 and 2 say "agree". Ive seen a few Throttle bodies go bad and mirror other issues, i.e. HPFP etc.
    also might check the MAP sensor, should be between 3.8 and 7.5 psi I believe. and should change with throttle input. also just make sure the air filter isnt clogged. hope some of that helps!!

  15. #15
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    purge solenoid stuck open or leaking sucking gas from evap canister? hopefully you dont have aftermarket o2 sensors giving false readings
    cats plugged causing low airflow? i think maf tops out around 260 g/sec under wot in those trucks

  16. #16
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    Quote Originally Posted by Estep40511 View Post
    also might check the MAP sensor, should be between 3.8 and 7.5 psi I believe. and should change with throttle input. also just make sure the air filter isnt clogged. hope some of that helps!!
    New Air filter, have two different throttle bodies, the stock one and a lingenfelter tb. Swapped tb no difference

  17. #17
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    Quote Originally Posted by noia_05 View Post
    purge solenoid stuck open or leaking sucking gas from evap canister? hopefully you dont have aftermarket o2 sensors giving false readings
    cats plugged causing low airflow? i think maf tops out around 260 g/sec under wot in those trucks
    Dealership checked the evap canister. Wait what... is the purge solenoid supposed to wiggle? Hmm think I'm going to replace that. As far as the cats they have a slight brownish orange tint to them, but look clear.

  18. #18
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    Ok! i have done a lot of research and replaced every sensor and EASY part on my truck so far and am still getting this issue as well
    Random missfire, C7 missfire, C4 Missfire, C6 missfire, C1 Missfire, Squeeky lifter, BAD TIMING, O2 sensor

    I have replaced all of the folowing
    MAF, Intake manifold from 5.3-6.2 and Throttle Body, Exhaust full, O2 Sensors, Knock sensors, Cam shaft sensor, Water temp sensor, High pressure fuel pump, In tank Fuel pump, Fuel Rails, Injectors, coil packs, spark plugs, spark plug wires, The list goes on.....
    It boils down to the factory parts from Cheverolet that they refuse to admit are causing the issue (hints the class action lawsuit.) I 100% believe that this problem is caused 2x fold by 2x separate components.

    The first is the DOD SYSTEM, and no, turning it off does NOT fix this!!!! the DOD system is run off of oil pressure, it travels down the center of the block to the 4 oil pumps under the intake manifold, that in turn feeds the lifters and allows them to collapse during operation to "shut off" a number of cylinders, the Excess of parts (AKA springs for the collapsible lifters) for this system are prone to failure under load and must be removed or replaced with NON DOD, LS7 lifters or something similar. when these springs wear out or when the locking device fails it can leave a lifter stuck in the "closed position" this is cause for a misfire either it wont let air in or exhaust out, can you guess where this is going?

    The second problem is with the Camshaft Phazer itself. under heavy load the phazer spring will be maxed out until the load is balanced and the spring has a small chance to return to its normal position. this retards the camshaft, and after a short while, resets it to the normal position. "Saving fuel and reducing power" Over time with an upgraded motor, or even a tuned motor this spring will wear out and cause the motor to idle spastic. this can happen to the extent of Backfire in the intake (ITS PLASTIC) Hello Chevy? or running extremely rich throwing off your O2 sensors or your MAF. This use of springs in a modern motor is definitely left something to be desired. you can either get a camshaft Phazer limiter from Comp. or you can pick up a timing chain sprocket from LME (Late Model Engines). the camshaft sprocket degree's pattern of the gen 5, vs the gen 4 and 3 is different by several degrees. Please do not put gen 4 parts on your GEN 5

    over all the DOD "collapsible" lifters, the DOD oil pressure pumps under the Intake manifold "that plate" The Camshaft Phazer and the Camshaft Bolt, make for a catastrophic combination too ones mode of transportation and can leave you stranded at the most in-opportune moments.

    parts list for replacement
    Camshaft sprocket from LME or with the correct timing, Or a Phazer Limiter from Comp. GEN V only,
    LS7 Lifters,
    camshaft of your choice (what you have HP tuners, put it to some good use)
    full top end gasket set(heads, Valve Covers, Timing cover, water pump, Fresh Head bolts "TTY"),
    Oil Gally pump Plugs, Remove the Oil Pumps, or replace the Cap with a Pump less cap! check out Texas speed.

    I am not a Mechanic or a tuning pro this is just my thoughts and research on a otherwise "Sore Subject" (Please do your own research before taking some guys advice and investing money in parts)
    If i have left anything out or forget to mention anything please let me know so we can all be on the same page when it comes to tuning these GEN V trucks and cars.
    one day my truck will be cool again

  19. #19
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    Sorry you had to go through all that just to end up where so many of us have already been: a failed DOD lifter.

    I'm running the Gwatney Performance Stg 1 truck cam and absolutely love it. Super docile for a daily driver, idles rock-steady and pulls nicely to 5800 if I spin it that high. I commute to work 70 miles each day with this cam and haven't had as much as a hiccup with it.

  20. #20
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    brokenlog.hpl here is the log. still messed up.
    now I also have these besides the misfire and lack of power.
    0x7E8: P0068 - MAP / MAF - Throttle Position Correlation (Permanent)
    0x7E8: P0097 - Intake Air Temperature Sensor 2 Circuit Low (Permanent)
    0x7E8: P00F4 - Humidity Sensor Circuit Low (Permanent)
    0x7E8: P0102 - Mass or Volume Air Flow A Circuit Low (Permanent)

    already thinking of trading this in because of the problem.