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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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[quote=”Evil-i” post=168522]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.[/quote]
Appreciate the reply, I thought that the engine could be lugging at first but I keep reading everywhere that you can’t lug an automatic but I guess if its not downshifting properly than it could lug somehow. However after the dealer reprogrammed the transmission I now notice the sound in 3rd gear at 2000 rpm, 4th gear at 1200 and 3000 rpm as well as in 6th gear at approx. 1500 rpm. If it is lugging it seems odd its lugging more after the reprogram.
From what I read in doing research on the skyactiv, it seems that some people have had to press the accelerator pedal pretty far down in order to get the A/T to downshift and that 1500-2000 rpm in 5th is the normal cruising RPMs for a skyactiv. You are right though, if I am hearing the sound in 5th gear and manually downshift to 4th the sound does seem to go away most of the time.
The SkyActiv A/T locks its torque converter at about 30 mph. So it acts “mostly” like a manual transmission after that. While it could be a worn motor mount, it seems unlikely in a car with so few miles on it. I don’t think that with a computer controlled transmission that an A/T would lug so badly. Also, if I recall correctly, the SkyActive engine is designed to make decent torque at a fairly low rpm and lugging would not be my first guess.. However, the problem is that if there are no engine / transmission codes stored, then most techs will say something like (“bring it back when there’s a noticeable problem.”) Not because they don’t want to help, but if you replace a part and then that isn’t it, who pays?
I agree, the thing that has me confused is that the sound is similar to lugging but my thinking is the same as yours. The skyactiv is supposed to run at very low RPMs in higher gears to increase MPG and i’m just driving it normally so it would be seem odd that the factory would program the A/T in such a way that the engine would “lug” at these lower RPMs and possibly cause engine damage. Speed limits around me are mostly 35 mph and i’m usually in 5th gear at 1500 rpms by then and thats when I notice the sound the most.
When I took the car to the dealer for them to check it out, the tech said he could not hear any noise and they did not find any stored engine/transmission codes. So they told me to bring it back another time if it keeps making the sound. The tech did say that my description sounds like engine lugging but he was not sure how that would be possible given that its an A/T.
It looks like the 2012 2.0 makes about 125 ft/lb of torque at 1500 rpm and about 130 ft/lb at 2000 rpm.
[quote=”Zerobdr78″ post=168543]The tech did say that my description sounds like engine lugging but he was not sure how that would be possible given that its an A/T.[/quote]
5th gear is an overdrive gear, and 4th probably is too. To my way of thinking, the transmission should be downshifting to 3rd gear when you press on the accelerator.
You just aren’t going to get anything but lugging if the transmission remains in an overdrive gear when acceleration is called for, and lugging is accompanied by asthmatic exhaust and intake sounds.
Yeah if I press on the accelerator about halfway it will downshift to 4th gear and it will accelerate normally. It Your thinking definitely makes sense, its just that if i’m only wanting to maintain speed i’m forced to lightly accelerate and hear the noise. I guess I have to either increase speed to get the RPMs up or just find a reasonable speed where the RPMs stay out of the lower range.
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