5.0 poor mileage and idle hunt/fluctuation - Page 2
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Thread: 5.0 poor mileage and idle hunt/fluctuation

  1. #16
    FRESHMAN ROVER
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    Quote Originally Posted by bill2019 View Post
    I found this video to help you understand it a bit more. Perfect example of a faulty High pressure fuel pump and it possible symptoms. Found and fixed by a pro.
    https://www.youtube.com/watch?v=GlK-BZuq8K8
    I did check the oil, seemed fine. Changed the oil and filter today. Wouldn’t a leaking fuel pump affect both banks?

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  3. #17
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    no you would have two one for each rail. But either way the vapor would be reentering through the breather to intake manifold.

    Keep in mind that in your case it may not be this, I was only going on several of your symptoms
    2019 Range Rover Sport HSE Dynamic

  4. #18
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    The high pressure fuel pump delivery circuit works in a "compound" manner.

    Both pumps are driven by an auxiliary cam, which is also common to the oil pump. The high pressure (HP) fuel demand is regulated by the ECM, using multiple measured inputs.

    The HP pumps are plumbed through conjoined delivery pipes and thus the high pressure fuel is measured as a combination of the two, not individually (or per rail). The psi at high HP demand can be in the 2000 psi range (yes, two thousand psi).

    Usually, if experiencing HP problems both pumps are replaced. Although an individual pump may fail, that would require "guessing" or tossing a coin as to which one was faulty, replacing it then running through the diagnostic procedure again. They are a pain to replace.

    If you "guessed" wrong you'd have to go through the exercise again. That gets expensive for the labor portion. I get that if someone's on a limited budget that that may be worth their time. Their car, their choice but the combination for labor and parts is probably a wash regarding replacing both pumps at the same time (like most good shop practice, although replacing "paired" systems at the same time may mean a slightly shorter service life than expected for the non-faulty part, paying twice for the independent replacements is usually a little more expensive in the long run).

    Rob

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  6. #19
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    I don't think its a fuel pump issue, as the problem is only on one bank.

  7. #20
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    Ok has all 4 VVTs replaced. Had to be done, one was clearly problematic. So opted to do them all. Nasty noise is now gone, engine quiet. But still have the negative LTFT on bank 2 under idle / low load conditions, even at highway spead. High RPM or higher loads evens out the LTFT.

    I did did my homework on the fuel system, and learned a bit, but some things are unclear.

    Am I understanding it correct that each bank has its own separate pump and rail? Could it be possible that one side is over-supplying? I think the other possibility is a leaking injector but all 8 are new.

    another symptom: idle ignition advance is only at +2-3 deg. I think usually it would be much higher. As I understand it, ignition timing can be used to control and or smooth out idle, bust mostly for non drive-by-wire. Not sure if relevant here but seems very low for no load at idle. Seems normal under all other conditions.

  8. #21
    JUNIOR ROVER MARK_C's Avatar
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    Bank 1 is the right side of the engine (Passenger side in NA), Bank 2 is left side of the engine, (drivers side in NA). The SC engines have a separate SC cooling system so the temp 2 reading may be coming from the coolant temperature on the SC loop) Your Bank 1 fuel trims are slightly lean but still in the good zone, your Bank 2 fuel trims are way lean, and if you don't have it now, you will probably be seeing the P0172 pre cat lean DTC soon.
    M Canning
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  9. #22
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    Quote Originally Posted by MARK_C View Post
    Bank 1 is the right side of the engine (Passenger side in NA), Bank 2 is left side of the engine, (drivers side in NA). The SC engines have a separate SC cooling system so the temp 2 reading may be coming from the coolant temperature on the SC loop) Your Bank 1 fuel trims are slightly lean but still in the good zone, your Bank 2 fuel trims are way lean, and if you don't have it now, you will probably be seeing the P0172 pre cat lean DTC soon.
    If I’m not mistaken, a negative LTFT means the bank is running rich, and it’s reducing the percentage of fuel from base map. I am running rich, not lean..

  10. #23
    JUNIOR ROVER MARK_C's Avatar
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    I think it depends on how you are getting your LTFT data, SDD shows lean as positive numbers and rich as negative, but a generic code reader shows lean as a negative number and rich as a positive number.
    M Canning
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  11. #24
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    Quote Originally Posted by MARK_C View Post
    I think it depends on how you are getting your LTFT data, SDD shows lean as positive numbers and rich as negative, but a generic code reader shows lean as a negative number and rich as a positive number.
    Using IIDT tool. So negative should be a rich condition.

  12. #25
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    Agreed, should be running rich. Which points to things like a plugged up (dirty) air filter, a (or multi) failed injector, maybe a dirty throttle body which on the 09 and previous L322 SC engines are a bit of a pain to get to being in the rear of the intake manifold (don't know where they are on a 5.0 engine) or possibly just a messed up ECU program telling the injectors to pump more fuel that is actually required. What kind of numbers are showing up on your pre cat O2 sensors. Do they indicate a rich mixture, or do they seem reasonable?

    If the CAT with the 0420 code is really plugged the engine can just be struggling to make up for the loss of power caused by less exhaust flow on that side. I had a cat plug on a throttle bodied engine years ago and it was like I have lost 1/2 the cylinders, and i bet that CAT glowed bright red before it completely burned out.
    M Canning
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  13. #26
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    Quote Originally Posted by MARK_C View Post
    Agreed, should be running rich. Which points to things like a plugged up (dirty) air filter, a (or multi) failed injector, maybe a dirty throttle body which on the 09 and previous L322 SC engines are a bit of a pain to get to being in the rear of the intake manifold (don't know where they are on a 5.0 engine) or possibly just a messed up ECU program telling the injectors to pump more fuel that is actually required. What kind of numbers are showing up on your pre cat O2 sensors. Do they indicate a rich mixture, or do they seem reasonable?

    If the CAT with the 0420 code is really plugged the engine can just be struggling to make up for the loss of power caused by less exhaust flow on that side. I had a cat plug on a throttle bodied engine years ago and it was like I have lost 1/2 the cylinders, and i bet that CAT glowed bright red before it completely burned out.
    Blower and throttle body have been off and re sealed/cleaned. the Bank 2 pre-cat 02s showing -11 to -14% under light load. -5 to -8% on medium to heavy loads. Bank 1 is always around -1% to -3%. sometimes zero.

    The Bank 1 cat : pulled it out, scoped and inspected, and found some physical exterior damage from off-roading, and a tiny sliver of honeycomb was missing inside. Not plugged. Bank 2 looks fine. so its seems like an un-related problem.

    Now I just drive around comparing whatever parameters I can to find more anomalies, and noticed the following:

    Valve timing (VCT): both banks equal, within 1 degree, changing timing as requested by PCM
    Valve lift control (LR Speak: CPS, aka Camshaft Profile Switching) not working. I never get into high lift mode when under high load and high RPM. always staying in low-lift mode, no matter what

    When I check for misfire counters on individual cylinders, I dont get anything. When I check for total combined events, I get a number showing.

    When I check the parameter for "Combined misfire information - fuel cut-off execution flag bank1 (or bank 2), i get activity here. But I get Bank 1 showing "true" for this on occasion..
    Is there a better way to see if I am getting misfires?

    If bank 2 has its own HPFP on its own circuit, maybe that is the cuplrit.. because from what I can see, there is only one pressure sensor, and its on the Bank 1 circuit.

  14. #27
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    A misfire (or multiple misfires) are obvious when driving as the vehicle will judder as the misfiring cylinder(s) drop off and exhibit themselves.

    Are you experiencing any juddering under different throttle/rev settings?

    Does the car drive normally during cold start then begin any pronounced judder when driven (at any particular RPM ie 1800rpm on the highway) once it's reached normal operating temperature?

    Are your normal operating temperature cylinder compressions all in the 180-200 psi range?

    Are you using SDD as the diagnostic platform?

    If you're using SDD there are a couple of ways to detect/monitor misfires.

    Given that you're aware of your VVT angles it's likely you're using the less capable of the two options. I'm guessing the page you reference has the VVT angle readings across the top and the eight individual cylinder references below in two horizontal columns?


    Rob

  15. #28
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    Quote Originally Posted by anvilrob View Post
    A misfire (or multiple misfires) are obvious when driving as the vehicle will judder as the misfiring cylinder(s) drop off and exhibit themselves.

    Are you experiencing any juddering under different throttle/rev settings?
    Juddering, no. just RPM fluxuation

    Does the car drive normally during cold start then begin any pronounced judder when driven (at any particular RPM ie 1800rpm on the highway) once it's reached normal operating temperature?
    Drivability is roughly the same when warm or cold. Cold start gets a little high on RPM (revs too high and stays kinda high). But this symptom also occurs when hot, just not as bad.

    Are your normal operating temperature cylinder compressions all in the 180-200 psi range?
    Have not done a compression test yet.

    Are you using SDD as the diagnostic platform?
    No, using GAP tool.

    If you're using SDD there are a couple of ways to detect/monitor misfires.

    Given that you're aware of your VVT angles it's likely you're using the less capable of the two options. I'm guessing the page you reference has the VVT angle readings across the top and the eight individual cylinder references below in two horizontal columns?


    Rob
    No, just using IIDTool, which lets me pick any 8 parameters I want.

    Going back in to my repair shop to check the fuel pumps and a few other things

    Also, just a side note - while the S/C was off for VVT actuator replacement, I had the intake valves walnut blasted. All clean now. They weren't horrible, but weren't great.

  16. #29
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    OK,

    Here's a printed out copy of the SDD screen results of the two depictions I was referring to (below).

    I was working on this normally aspirated MY2010 5.0 this past Saturday. Note, the car is running during both tests.

    The panel with the VVT displays zero misfire(s) while idling in the shop, yet the second more appropriate panel with just the misfire detection annotated data selected displays multiple misfires during a follow-on road test with an observer.

    5.0 poor mileage and idle hunt/fluctuation-vvtplusmisfire1justmisfire2.jpg

    5.0 poor mileage and idle hunt/fluctuation-activemisfire-detection.jpg

    If the shop you're using has SDD make sure they/you use the second/lower option and have TWO people on board, then take the vehicle for a test drive to monitor the data regarding possible misfire(s).

    One person drives, the other monitors the data from the passenger seat (unless you almost want to guarantee a wreck).

    The "Current column" is the number of misfires during THAT drive. The "Average column" is a cumulative detective record and although it may look less bold in the printout, the left side number is actually depicted in green on the computer.

    Before going any further, it's worth taking the time to do a compression check prior to spending any more money on parts - you need to make sure the motor is mechanically "well enough" as is.

    Good luck,

    Rob

    PS The first thing I did on this vehicle was check its normal operating temperature compressions (all good). No point trying to troubleshoot an external issue if the thing's worn out on the inside

  17. #30
    SOLIHULL ROVER Mrmerlin's Avatar
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    Re: 5.0 poor mileage and idle hunt/fluctuation

    Brav watch that video that Bill posted.
    Thanks for the info Bill.
    Stan

    2010 Supercharged, Santorini Black/ BlackLeather/Piano Black wood

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