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Hey all,
About 2 weeks ago I purchased a used A/T 2012 Mazda 3 I touring 2.0L Skyactiv with 45,000 miles on it. Soon after purchase I noticed the engine was making a deep sounding rumble/humming noise upon acceleration, mostly while in 5th gear between 1500-2000 rpm. This sound is much deeper and does not sound like normal engine noise.
While this sound is being made, the engine seems to accelerate very slowly despite me pushing the pedal halfway down. Its as if the engine is “bogging” down and if I press more than halfway down on the pedal, the rpms jump up to 2200 rpm and the engine goes back to normal. I also get this same noise in 4th gear but only at 1200 rpm. I noticed the sound mostly while on the highway and while on town roads.
This sound is different than the metallic rattle/gurgling type sound that seems to be common with skyactivs. I took the car to the dealer but held off on paying the $130 diagnostic fee they wanted to charge until I could maybe figure out if it was something worth getting looked at.
Is this a normal sound from skyactivs and if not what could the cause be? I appreciate any help!
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Sounds to me like you’re in the wrong gear for accelerating at that RPM range and you’re lugging the engine. Try downshifting to 4th or even 3rd.
EDIT: Sorry, just noticed you’re driving an automatic. I’m no transmission expert, but your transmission isn’t kicking down when it should. Fluid level would be the first thing to look at. Also check for leaks and wetness under the car.
Thanks for the reply!
I checked the owners manual and it said that the car should be in 5th gear at about 34mph and 6th gear at 45mph. It seems that the A/T skyactivs are geared to get into the highest gear as quickly as possible to conserve fuel and increase mpgs. Maybe the engine is lugging somehow because of this skyactiv gearing.
I looked under the car and didn’t notice any leaks or wetness. Ill be sure to check the trans. fluid level. According to Mazda the skyactiv has a semi-sealed transmission and Mazda says the transmission fluid is good for the life of the car. I’m always a little skeptical of the trans. fluid being good for life, so when I get a chance ill most likely do a trans. fluid change and see if that could fix the engine noise.
Just an update: I checked the transmission fluid level seemed overfilled, I doubt the fluid has been changed since factory fill. The color of the fluid looked ok, it was a deep golden color (Brand new skyactiv trans. fluid should be a light blue color).
I also talked to a Mazda dealer over the phone and told them my problem. They said that the sound could be normal for the car. According to the dealer, the Skyactivs have a redesigned A/T and the torque converter can be noisy at times. The dealer said this could be what is making the deep humming noise and slow acceleration in 5th gear. The dealer suggested driving it around for a few more weeks before making a service appointment.
Still not sure if its normal or not.
The issue I see here is that the dealer is expecting you to live with a potentially dangerous condition. When you step on the gas pedal, you expect the car to giddyup and go, not chug along and make strange noises. Could be dangerous when merging into highway traffic and such.
I wouldn’t be too fixated on the noise; the car’s response to throttle input is the issue.
Are you positive your not hearing a wheel bearing noise? The skyactiv is generally a fairly quiet engine
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Yeah the sound is annoying but something I could live with. I agree that the acceleration problem is the bigger issue. It is really a pain when cruising on the highway and you need power to pass someone.
And yeah I am almost positive it is not a wheel bearing noise. This sound is much deeper and almost sounds like an aftermarket exhaust type noise. Except everything is stock. The sound also seems to come and go at exactly the same rpm every time.
If the engine is “lugging”, laboring under acceleration because the transmission hasn’t shifted into the proper gear, you’re going to experience unusual intake and exhaust noises.
I would definitely think the sound would be from lugging but I looked up the speed at which the transmission should be shifting into each gear in the owners manual and it seems that the transmission is shifting into the right gears at the right mph. The only time I hear the sound is usually in 5th gear which the transmission shifts into once the speed reaches 35 mph.
There is a Technical Service Bulletin out from Mazda that affects my car stating that the transmission may experience “shift shock” in certain gears due to not being properly programmed from the factory. Not sure if somehow an improperly programmed transmission could be causing my problem even though the “shift shock” symptom doesnt really apply to me.
I also disconnected the battery to try to reset the ECU. The sound and slow acceleration seemed to have improved a little since then although the problem is still there.
Just an update: I took the car to a local dealer and of course when I took a drive with the tech, the car didn’t make the noise despite it making the noise just yesterday. The sound seems to be more easily heard on certain road surfaces.
As for the slow acceleration in 5th gear, the tech said that it’s a common problem with some of the 2.0I skyactiv engines. He said he will reflash the PCM which should fix the problem.
One last update: After driving the car for nearly a week after the dealer reflashed the PCM, it seems to have not helped my problem. It seems now that the low sounding growling/humming noise when accelerating is more pronounced and seems to occur in other gears besides 4th and 5th. The only thing the PCM reflash seemed to mildly help was the acceleration responsiveness. I am still not sure what is causing the problem I know the Skyactiv is a DI engine so maybe it could be intake valve deposits causing problems or just a characteristic of the engine.
The sound is concerning because it sounds like the engine could be lugging but its an automatic. Is there an off chance my car could somehow be lugging and the noise is causing engine damage? The tech at the dealer mentioned that the symptoms I described sounded like engine lugging.
Since you specifically say that the sound mostly occurs on certain roads or road surfaces, I think that it sounds like a tire issue. Of course you could only prove this by putting different tires on it. However, the one thing that I would suggest is that if you have the A/T. You can manually shift this transmission. You don’t have to race the engine, but just for kicks you may want to use this feature to run through the gears and see if the sound is more noticeable at certain RPM (like: it always sounds weird at 3500rpm for example.) I have the 2.5L Mazda 3. I only notice a funny sound when the car first starts from being cold. It has a high rpm function to heat up the catalyst and, to me, it sounds (at that point) like it has a hole in the muffler – even though it doesn’t.
Thanks for the reply! I’m pretty sure its not a tire issue but rather something with the engine or transmission (I’m hoping i’m wrong). It not that its only heard on a certain type of road surface but its more easily heard when there isn’t a lot of road noise. The dealer had a concrete road in front of them which seemed to create more road noise and make the sound harder to hear. The slight pedal vibration on acceleration is still there no matter what road surface its driving on. It could be an exhaust issue too but I would think it would make the sound no matter what RPM i’m at.
I tried putting the car in manumatic mode and can easily reproduce the sound/slow acceleration at the same RPMs when manually shifting through the gears. I heard that the low rpm rumbling noise could just be a characteristic of the skyactiv engines. Is your 2.5l a skyactiv or the MZR engine?
I have a 2016, SkyActiv engine.
The reason that I feel it’s a tire issue is that at certain speeds an out of balance or slightly damaged wheel or tire can spin to speed that creates a harmonic vibration. At that speed, the wheel will “sing” but above or below that speed, it’ll be silent. I just don’t see an engine or transmission making a thrumming sound. It should be more of a constant, like a bearing growl, or a tappet click that increases and decreases with engine rpm. Anyway, I hope that you enjoy the car and don’t have any serious problems with it.
That makes sense, I know prior to purchasing the car the dealer had put new tires on it but they are cheap branded tires, so maybe that could explain the noise. Perhaps higher quality tires would help the noise. The thing that is confusing me is the slow acceleration part that happens at the same time i’m hearing the noise. As soon as the noise disappears, the acceleration goes back to normal. It does sound very similar to a hole in the muffler but I didn’t notice anything unusual with the exhaust system when I looked under the car.
Would the tire noise be something that only occurs when your are lightly accelerating? As soon as I take my foot off the pedal the noise goes away even if i’m still in 5th gear at the 1500-2000 rpm range I normally hear the sound at. I love the car and enjoy driving it, just can’t help but think if this noise isn’t the tires that I could be damaging the engine somehow.
I said it before, I’ll say it again. In 5th gear, (an overdrive gear), and at such low rpm, you can’t expect much in the way of acceleration when you press the gas pedal.
The sounds you are hearing are most likely a symptom of lugging the engine. Try driving the car and reproducing the noise at that rpm, in that gear, while accelerating. Manually shift into a lower gear and the sound should cease, and the car should accelerate with more aplomb.
Lugging the engine puts wear-inducing stresses on your engine bearings. The engine isn’t spinning high enough to produce sufficient oil pressure to support the extra work you’re asking the crankshaft to do. Don’t be afraid to rev the engine higher by downshifting. That’s what’s supposed to happen when you tromp on the accelerator.
I still say it sounds like you have an issue of the transmission not downshifting properly when it’s supposed to.
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