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Thread: Engine rattle when accelerating

  1. #1
    evgeny is offline New Member
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    Default Engine rattle when accelerating

    Hi guys,

    wondering if anyone can help me out with finding what it is. Any suggestions will be appreciated.

    So this is what happened:
    Harmonic balancer was off. The engine was cranked. So the timing got way off.
    The timing was then aligned almost perfectly without the two SSTs.
    On stock tune the car ran fine without a single weird noise or performance issue.
    With a modified stage 2 map (cobb) it made a rattle around 3k-3.5K and then i immediately backed off.
    Put it back to stock tune and thought the problem was related to no having the timing 100% spot on.
    Now i ordered the SSTs and got the timing spot on. Same thing is happening - no noise or issues with stock map. But massive rattle that starts at 3k-3.5k with a tuned map.

    Now this is very weird because if valves got bent during the cranking then why no noise on stock map?
    Compression results: 150,160,160,160 which to me looks good.
    There are no performance drops on stock map and absolutely no rattles.
    Obviously this happened because the engine was cranked with no harmonic balancer, but I can't figure out what is broken. It is coming from the drivers side of the motor. The noise doesn't happen when car is stationary and is revved. Only on hard acceleration. The knock sensor detects sever knock and pulls the timing when this happens.

    my suspicions are: either vvt actuator got destroyed during the cranking or timing chain is too loose.

    OK i think that's about all i know about what happened to the car thanks guys

  2. #2
    RedDjinn is offline Slip stream
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    Could be the chain slapping on a chain guide or VVT. To get knock bad id think more something in the bottom end...

  3. #3
    Doug_MPS6's Avatar
    Doug_MPS6 is offline Forum Freak
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    It sounds like a lot has been happening in the timing department and this is just a guess but it still sounds like the timing is out of whack to me. It's not uncommon to have no per-ignition when stationary revving with no load, but around 3000 rpm under load a knock would be unsurprising, especially if the noise goes when you back off. A loose chain would tend to rattle all the time. I'd dump the tune mod (temporarily) if possible and go back to a defined stock start point and re-time the engine and get it running right. If you still have a rattle then you can chase the problem elsewhere. I see you have essentially done that (maybe twice), and given that you have no rattle on stock settings, then it's looking like a crook map to me.

    As a partly unrelated issue, if it is coming from RHS on the engine (as seen from drivers seat), then the air-con tensioner idler pulley bearing can fail and make quite a rattle too, although this seems unlikey in this scenario.
    Last edited by Doug_MPS6; 26-03-2013 at 02:46 PM.
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  4. #4
    Jmac's Avatar
    Jmac is offline Admin & Team JFat
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    If it was me.. Take it to a workshop and put it on the dyno so you can watch timing and compare the two maps in a controlled environment

    Sent from my Nexus 4 using Tapatalk 2

  5. #5
    MPS2NV's Avatar
    MPS2NV is offline Resident Filth Monger
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    I would suggest a leak down test and once you get the tools recheck the engine timing. If a bore scope is available maybe have a quick visual down plug holes. Maybe also check hpfp threads.

  6. #6
    AzA's Avatar
    AzA
    AzA is offline Junior Member
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    Any solution to this issue? I have the same issue, just had my VVT and timing chain replaced. Same thing, 3rd gear WOT and sounds like a loud rattle; like spray cans in the engine, basically pings any time engine is under load. I am leaning towards the possibility the the crankshaft position sensor was not correctly aligned, causing timing advance?

    Can anyone confirm my theory?

  7. #7
    auscer's Avatar
    auscer is offline Stay at home dad FTW
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    I have a engine rattle but mine is a bearing going pretty sure air con or starter

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  8. #8
    chef is offline Forum Freak
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    I would follow jmacs advice.i wouldn't be trying to do this on my own

  9. #9
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    Quote Originally Posted by AzA View Post
    Any solution to this issue? I have the same issue, just had my VVT and timing chain replaced. Same thing, 3rd gear WOT and sounds like a loud rattle; like spray cans in the engine, basically pings any time engine is under load. I am leaning towards the possibility the the crankshaft position sensor was not correctly aligned, causing timing advance?

    Can anyone confirm my theory?
    Okay, One suggestion, and two questions.

    DO NOT boost your car while it is apparently detonating. If the detonation is bad enough that the ecu cannot back off timing enough to stop it, then you are going to blow your engine up.

    Is your car tuned?

    Who did your timing chain and VVT?

    I have said it again and again, but I will repeat it here.

    The timing setup on our cars is very easy to stuff up. There have been numerous instances of even highly skilled shops replacing timing chains and either mis-aligning timing, or possibly not torquing the crank bolt properly and having crank slip. Both of which can put your motor at extreme risk of blowing the shit out of itself.

    The timing chain area of the MZR motor is not overly hard to do but requires following mazda procedures to the letter, which obviously some places have not done.

    You need to get your car checked asap, otherwise you will either damage something internally, or potentially destroy your engine.
    MPS is gone. Ghey Trail enabled....Not Happy. MPS 6 to come

  10. #10
    AzA's Avatar
    AzA
    AzA is offline Junior Member
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    Thanks for advise Littered MPS!
    Fortunately we solved the problem. We moved the crank position sensor today, turned it anti clockwise of its previous position. No more rattle, car runs great!
    I will be taking to Mazda next weekend and have them hook up their diagnostic equipment and double check everything.

  11. #11
    RadiantKnackers's Avatar
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    Quote Originally Posted by AzA View Post
    Thanks for advise Littered MPS!
    Fortunately we solved the problem. We moved the crank position sensor today, turned it anti clockwise of its previous position. No more rattle, car runs great!
    I will be taking to Mazda next weekend and have them hook up their diagnostic equipment and double check everything.
    Good stuff mate. Glad it was an easy fix
    MPS is gone. Ghey Trail enabled....Not Happy. MPS 6 to come

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