Constant knock that follows rpms please help!!!

[Edwards3893]

So recently I bought a 2012 Mazdaspeed 3 has 100k on the dash. This car is literally bone stock all the way threw. After buying it I started to hear more of a constant knocking/rolling sound at idle and the speed of the sound increases with RPMs I can hear the sound inside the car easily but when I try to use a scope to listen to the motor the noise sounds like it’s dispersed through out the whole engine it sounds loud on the turbo and exhaust but as well as the top of the motor. I just recently just got codes for p0300 that just came up and I smell gas in the cabin of the car as well now please help. I have had one shop tell me piston slap and another tell me lifter and rocker arm. It does not seem like I have any loss of power at all. And also when I start the car up after it has sat for a while it makes an ungodly knocking/rattling noise for litterally 1 second till the car is fully running. Here are 2 videos to help one in the cab of the car another on the passenger side of the motor because I hear it better on that side
https://youtu.be/-vKEZ8gZCxc
https://youtu.be/zJ-lsNYOfdw

[Fstrnyou]

Threw: past tense of throw.

Example: My engine THREW a rod yesterday because my car has problems and I drove it anyway. The rod went THROUGH the side of the block. Because I didn't read this magnificent website THOROUGHLY THROUGH and THROUGH, now I'm THROUGH with Mazdaspeed and THROWING in the towel.

Any THOUGHTS THOUGH?

[Edwards3893]

Sorry for my grammar.... I am dyslexic and struggle with common grammar sometimes. Other then that I’m not an idiot by any means. I just need help with my car ��. I don’t know what it could be ����—♂️ The noise is the loudest on the back side of the motor but I’m having issues trying to hunt it down. It sounds to be coming from the turbo maybe exhaust side of it when I put my scope on it you can hear it in the turbo very loud and clear but you also can hear it very well on the back side of the valve cover/head

[Bertospeed3]

Damn, now i feel bad for laughing

[SSinstaller]

Your knocking sound reminds me of the intro to every bent rod story Ive ever read. Also, you should pull the valvecover and inspect the VVT actuator, that could be your crazy rattle at startup.

[Edwards3893]

So is the only way to see if it’s a bent rod is to take it out (aka motor rebuild why I’m there) would a compression test tell anything on a bent rod?

Also I don’t hear the knocking after a certain rpm because the motor will drain the noise out.

[Fstrnyou]

Ahh. Drown it out with the radio if you don't want to rev it too much.

[SSinstaller]

Originally Posted by Edwards3893 So is the only way to see if it’s a bent rod is to take it out (aka motor rebuild why I’m there) would a compression test tell anything on a bent rod? Also I don’t hear the knocking after a certain rpm because the motor will drain the noise out.

You could try a compression test- a bent rod would drop the compression in that cylinder, but it might not be that noticable on a high mileage motor. You could always just pull the oil pan and look.

[Fstrnyou]

There's always the screwdriver test for a bent rod.
Stick long screwdriver through sparkplug hole.
Crank manually to TDC and mark the height if the screwdriver. Repeat on other 3 cylinders.

But, like the compression test, it may be too small of a difference to notice.

[LenSpeed6]

@Fstrnyou; do you need a hug buddy?

[Jeff23spl]

unless you are skilled at checking rod height or have a followed historic of your engine compression. You would better remove the oil pan to inspect each top part of the rod bearing and if you see marks or color difference, you need a rebuild + crank work.

You can inspect timing chain and VVT, if chain is stretched or VVT is some kind of free, you call a timing job....

And don't return to the shop that said it could be a lifter or a rocker arm because it isn't a carburated old 350 V8... our engines don't have rocker and, lifter are solid...unless it ran without oil, the chance for too much valve play is very limited and if it do ran without oil pressure, the bottom end will fail a lot sooner than the top....

If you look for a pleasant and economic solution rise the volume until it ZZB.

[86AmishMs3]

Do a compression test. It will tell you what you need to know. Easy to rent.

[Edwards3893]

Thank you everyone that replied back I will try a compression test and see if that gives me anything! I’ll post my test in here once I get it done

[Gen2_MZDASP3]

I am having a similar issue with my speed3. My stock turbo failed at 84k after a lot of hard driving. Anyways I replaced the turbo and my air oil separator because it was cracked and leaking. I also did the timing chain, guides, gear and replaced my VVT solenoid because it was acting up (screen was clogged). Now when I drive the car under very little load it runs and drives perfectly. But under heavy load there is a loud clicking noise that follows RPM as well as backfiring out of the intake. I thought the valves were leaking so I cleaned them but it didn't solve it unfortunately. My compression is about 165psi on the end cylinders and 160psi in the middle. Anyone got any ideas as what it could be?

[MSMS3]

Originally Posted by Gen2_MZDASP3 I am having a similar issue with my speed3. My stock turbo failed at 84k after a lot of hard driving. Anyways I replaced the turbo and my air oil separator because it was cracked and leaking. I also did the timing chain, guides, gear and replaced my VVT solenoid because it was acting up (screen was clogged). Now when I drive the car under very little load it runs and drives perfectly. But under heavy load there is a loud clicking noise that follows RPM as well as backfiring out of the intake. I thought the valves were leaking so I cleaned them but it didn't solve it unfortunately. My compression is about 165psi on the end cylinders and 160psi in the middle. Anyone got any ideas as what it could be?

Sounds like you may not have gotten the timing set properly when you replaced the chain.

[Gen2_MZDASP3]

I thought the same thing but I checked it and so did 4 other techs I work with. It is definitely set right.