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Discussion Starter · #1 ·
After a repair on my 2.0L 2014 Mazda 3 (31,000 miles) by the Mazda dealership my engine has been having some very concerning sounds. The one I'm most worried about and that has recently popped up is a "jackhammer" type sound. It's almost like metal on metal or as if the engine had no oil. It does have plenty of oil. The repair they did was a oil valve control (gasket was leaking) along with a "seal" and a new head cover gasket. It's pretty concerning. I have video of the sound I will put on at the end of this paragraph. The intake also has this sort of hiss as if it was letting go of air pressure. I honestly don't get it with this car. So many issues so far (Been to dealership at least 6 times). Anybody have any ideas?

https://youtu.be/aIWnTMjRvuI
 

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Sounds like the direct injectors to me. All direct injected engines are much louder than the traditional fuel injectors. Sounds normal to me.
 

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Discussion Starter · #3 ·
Sounds like the direct injectors to me. All direct injected engines are much louder than the traditional fuel injectors. Sounds normal to me.
I sure hope so. I turned it on again and it seems much quieter. I think something with the temperature maybe. We'll see.
 

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Discussion Starter · #5 ·
Runs just fine, I never had direct injection so I thought it was some kind of metal on metal sound.
 

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I'm sure no expert, but I've had four DI engines and none of them sounded like that. But I have nothing to suggest except maybe take it back to the dealer for a check?
 

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Discussion Starter · #8 ·
Once again, that sounds quite normal. The sound is the injectors opening and closing. Nothing to worry about.
So the injectors open and close like a valve or what? and how does non-direct injection work if they don't open and close like these?
 

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It's been 7 months, is the car still running? Direct injection uses much higher fuel pressure, and the injectors go directly into the combustion chamber vs into the intake manifold. I think a lot of the extra noise is just the sound of the cylinder firing being transmitted up the injector body which doesn't happen on manifold injectors. But I'm just guessing. Sounds normal to me also.
 

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So the injectors open and close like a valve or what? and how does non-direct injection work if they don't open and close like these?
The injectors for DI and non DI are actually very similar. Its really just a valve as you suggest, held closed by a strong spring. When the ECU commands an injector to open, it energies an electromagnetic coil above the valve stopper inside the injector. This pulls it up opening the injector and admitting fuel to the engine. Once the ECU signal is lost, the spring forces the injector back closed.

The difference between DI and non DI is that the DI versions can react much faster. With a non DI engine, you have more time to spray fuel. The ECU can start spraying right after the combustion cycle, so that's 3 cycles. With DI the engine can only spray during the intake and maybe a bit into the compression cycle. That's why DI fuel pumps are much higher pressure. Less time to get the same fuel in.

So in short injectors clacking is very normal, even more so with DI. I remember the injectors in my old Hyundai used to tick away pretty good and that's was a non DI.
 

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4 cyl DI engines don't exactly sound the best. Noticed this with my old GTI and my gf's 2012 3 series. Even worse on the BMW, sounds like a diesel tractor.
 

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Discussion Starter · #13 ·
After 7 months yes the car is running perfectly with no hitches at 53k miles currently. I'm chalking it up to the design of the engine and nothing bad. :)
 
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