Knock sensor

Discussion in '2011+ Mustang GT 5.0L Tech' started by Powernexcess, Aug 9, 2017.

  1. Powernexcess

    Powernexcess Junior Member

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    New guy here! Can't figure out my problem , so I'm looking for some help.

    After Paxton install knock sensor will retard timing when shifting. I have something rubbing? , looking for ideas. Anybody have this problem? Exhaust and intercooler piping looks fine no rubbing.

    Thanks
     
  2. redfirepearlgt

    redfirepearlgt forum member

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    What does the tuner who tuned the car have to say about it?
     
  3. Powernexcess

    Powernexcess Junior Member

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    Said something is rubbing, but I can't find it. Looking for ideas or somebody that has had the same issue before.
     
  4. redfirepearlgt

    redfirepearlgt forum member

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    Since it sounds like the noise creating "False Knock" (assuming that is what is going on) is happening as the engine unloads and the reloads since it is occurring EVERY time (you did mean every time right? regardless of how hard you are on it?) check the following below.

    Check your exhaust system. Knocking sounds coming from exhaust coming in contact with the frame via hangers, etc., have been known to resonate at a frequency close enough to the tuned knock sensor range to cause your issue. Check rubber isolation points on exhaust system closely. Make sure the hanger of the muffler is not growing and vibrating against the inside of the rear bumper.

    Check motor mounts, recent tranny mount upgrades. to make sure there is not incidental contact there. I assume motor mounts are factory. If not and recently upgrade prior to problem that may be the issue. A polyurethane type material would not likely be hard enough to cause the issue.

    The rear end loading and unloading with solid linkage could also translate noise through the body into the engine block and cause "False Knock". So don't forget that either.

    Best of luck.
     
  5. Powernexcess

    Powernexcess Junior Member

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    Redfire, thanks for applying back. It happens when I shift under hard acceleration. I've looked at the exhaust over and over and can't see anything rubbing. The motor mounts are stock and the car is lowered 1" with lower control arms.
     
  6. redfirepearlgt

    redfirepearlgt forum member

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    Check the upper control arm? Is it factory? It could be failing. or a bushing in the LCA's could be popping if you have one failing on the bottom side. Additionally if running a UCA and upgraded bracket did the bracket get tightened to the correct torque spec when installed?

    Have you data logged just a series of hard third or fourth gear pulls (on a safe back road away from everything or on a dyno) first without shifting or activating the clutch and then reviewed the data logs for the problem return? Then a series of pulls only pressing in on the clutch and not shifting? Then a series with shifting gently so to speak? Then a series shifting spirited? Doing this may help isolate the area in which a possible interference noise is causing the False knock, such as only when you pressing the clutch, or only when you shift really quick.

    How much timing out of curiosity is the tuner putting in at WOT and how much timing is the knock sensor pulling? (remember minus numbers in the knock data are indications of adding timing and plus numbers are pulling timing) Further is this tuner telling you this and having you try to isolate the issue or are you actually seeing this in your datalogs and the tuner is claiming its False Knock? Is the tuner a legit tuner or is the tune some default tune that came with the Paxton package from Paxton in which Paxton offers a warranty on the drive train for newer cars like Edelbrock, Roush, and Vortech have done or still do? If it is a default Paxton tune I suggest you have potential protection strategies in the tune causing your problem and to consider another tune option. Just trying to think outside the box.

    No need to mention the tuner's name if it is a legit place. Just trying to rule out a few things , not smear someone;'s reputation.

    Otherwise I am exhausted of ideas and defer.
     
    Last edited: Aug 9, 2017
  7. 5lho

    5lho forum member

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    All the advice here is great. I had huge issues with this on my Vortech install on my '12. How do you know it is false knock? Here is how to tell: Real knock will start off high and gradually feed timing back in as time passes. Throw in some high octane fuel and real octane boost like Torco or Lucas and see if the situation improves. If it does, it's real knock retard.

    If it is false KR, look at EVERY connector on the hot and cold side. if they are even touching each other, inside the coupler, they can set this off. They can also set it off if they are touching ANYTHING, even plastic parts. Particular tight spots are the cold-side piping around the right side of the rad and sprayer bottle. Check every drive pulley, for quiet operation, as well as checking the exhaust from header to tailpipe, for any contact with anything.

    This is super aggravating, I know. It took forever to get my Vortech-powered '12 into something resembling decent running and then I wrecked it. With my replacement '14, I just put a nitrous kit on it and called it a day. I've been totally happy with that.

    Tell ya what...run a log and I'll even look at it for you. Here is what to include, as far as PIDs go:

    Lambse 1&2
    load
    LTFT 1&2
    STFT1&2
    Maf freq &flow rate in lb/min
    measured afr 1&2
    rpm
    spark adv
    spark adv v2
    throttle actual & demanded
    torque source
    knock sensor
    ECT
    IAT
    vehicle speed

    Give me a WOT run in one gear first, like 3rd, 2000-6500 rpm then a second one that has a shift in it. Be safe, this is a shit-load of power for street tires, if it works.
     
    Last edited: Aug 10, 2017
  8. Powernexcess

    Powernexcess Junior Member

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    It is very Frustrating! I had a 100 shot on before and have run way faster..lol. If i run a pull in any gear it has no knock. Only on a hard shift through the gears does it retard the timing. Didn't do it before the supercharger, so im lost on finding what's causing the noise.
     
  9. redfirepearlgt

    redfirepearlgt forum member

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    yeah but when you get it ironed out no trips to the store for a refill and never getting caught with an empty bottle. :clap:
     
  10. 5lho

    5lho forum member

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    Ok, if it's the shift, check closely for driveline movement, as well as all the other contact stuff. All the pipes are connected to the moving engine. Do you have a loop? they can move and touch the crossmember if not bolted on right. anything stiffening up the driveline, like a whiteline mount or poly engine mounts?
     
  11. Powernexcess

    Powernexcess Junior Member

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    I do have a driveshaft loop, but don't see any signs of rubbing anyplace? My lower control arms are bmr. Motor mounts are stock and other then lowering springs all other suspension is stock.
     
    Last edited: Aug 16, 2017
  12. 5lho

    5lho forum member

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    Something is touching under the load of the shift, that's certain.

    This'll make you laugh, I just pulled the intake manifold on my car and found one of the knock sensors unplugged...from the factory. WTG, Ford.

    The reason I pulled the manifold will also make you laugh, I just blew everything upstream of the cylinder heads to smithereens in a massive nitrous backfire.
     

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