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post #1 of 32 (permalink) Old 01-13-2014, 10:34 AM Thread Starter
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Shuddering Under Acceleration (Sometimes)

Hello, all.

I have a 2014 Touring and I have noticed that periodically, the car will shudder under acceleration. It particularly is noticeable when moderately accelerating in the 3000-4500 RPM range (not stepping into the kickdown switch, but at 80% throttle or so).

It can be felt mostly in the gas pedal and generally in the vehicle itself (the wheel doesn't wobble). It almost seems like the engine is quickly surging.

It does not do it every day, and I have not found any pattern to it yet.

Has anyone else experienced this? It is the AT model.
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post #2 of 32 (permalink) Old 01-13-2014, 05:03 PM
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No.

Usually if I had issues like that on older cars it was related to a sensor of some sort or coil packs misfiring. Too new for coil packs I'd think.

Never a bad idea to baby it and go to the dealership while under warranty.
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post #3 of 32 (permalink) Old 01-14-2014, 12:44 PM Thread Starter
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Originally Posted by wardorican View Post
No.

Usually if I had issues like that on older cars it was related to a sensor of some sort or coil packs misfiring. Too new for coil packs I'd think.

Never a bad idea to baby it and go to the dealership while under warranty.
Yeah - I've made an appointment with the dealer.

I have narrowed it down to second gear where it's the most noticeable.

I did read a TSB on the Mazda 3 that was related to winter fuels and what was a type of vapor lock when the fuel was fed through the high-pressure fuel pump. The additives would easily turn to vapor under heat and cause stuttering, etc. as the additives help with vaporization to help cold starting, etc. I know there was an ECU update for this.

Since I see it in the 30 degree range, I'm wondering if it's the winter blend gas causing the issue.

I guess we'll know on Thursday as that's when I take it in...
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post #4 of 32 (permalink) Old 01-16-2014, 11:10 PM
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New member! Formerly of the E36 BMW forums - decided to have a car instead of a constantly broken mantlepiece. At least hundreds of hours of taking apart and rebuilding cars could be worth something someday.

Anyways, I got this shudder deal, too. First gear wide open, second gear for the most part, then it dissipates for third, probably hidden under the multiplication of the gear ratios (and resultant frequencies).

Could be engine something-or-other (as mentioned above with the misfire). I was thinking possibly something in the transmission.

I've considered joining the forum to post about this. Ya beat me to it, but inspired me to join regardless.

I'm skeptical about dealers. Often times they stare at you blankly and write what you say down. Later, no one seems to know there was a problem, and it wasn't found. Just never seemed to happen under their control.
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post #5 of 32 (permalink) Old 01-17-2014, 02:52 PM
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I have noticed this in mine as well. I bought it at the end of August though, and we were definitely not using winter blend gas here in Houston then. Though I can't say I have experienced it recently. How many miles have you put on? I noticed it somewhere between 100-1000, and have just over 4000 now. I'm going to try on my way home tonight.

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post #6 of 32 (permalink) Old 01-17-2014, 06:06 PM
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6,000 miles on the odo, first gear a littler stronger vibration than second, not observable in third under any circumstances. Lots of warranty left, but - I hate stealers (dealers) with a passion and can see how this might play out with the wonderfully trained service staff!

I also noticed it does it at partial throttle, like the OP stated.
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post #7 of 32 (permalink) Old 01-20-2014, 10:26 AM Thread Starter
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I'm glad I'm not the only one.

I purchased the car in November. Noticed the issue at around 1000-1500 miles. The car now has 2200 on it. It performs decently when warmed up, although sometimes it's still apparent. I have noticed that it is worse when accelerating on on-ramps (cloverleaf) when there's a turn associated with uphill climb to the highway. I'm guessing it's load related.

Winter blend varies here, but it really came on with the very cold weather here at which point they would have put a ton of additives to help combustion/starting/emissions.

It is noticeable in first to some degree, second is the most prevalent, with all other gears fine.

The tech at the dealership stated that its the 'nature of the beast', although I don't think he was able to duplicate it. He did, however, seem knowledgeable and spoke with me for 10 minutes about the engine/transmission (I'm a tech/car junkie). The transmission shares clutch packs on 2-4-6 and 1-3-5, so if it was a mechanical issue in the transmission, it should show up. Also, he stated that at 7mph the converter goes into full lock-up on acceleration and uses a pre-load on the clutch packs for the next gear to facilitate a small amount of slip in between gears without having to unlock the converter.

No misfire showed up (cars will throw a MIL if they get too prevalent - with this issue, and how it feels, I think it'd throw a code).

At this point, I'm thinking it's gas blend and ECU tuning related to fuel pressure/flow/injector duty cycle. I do know from previous open-source tuning I've done that vehicles will change tables for timing/duty cycle on injectors, etc. based on current gear, load, temperature (intake), etc.

My plan is to pull the positive battery cable and let the ECU clear its learned tables. If the problem goes away, I'm thinking software. If not, then???
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post #8 of 32 (permalink) Old 01-21-2014, 07:17 AM
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Great reply!

In my mind I had pictured the converter lockup maybe not being 100% and giving some kind of pulsating feeling. At it's worst, the shuddering was noticeable by passengers in the vehicle who actually expressed concern something was about to break. It was felt in the steering wheel... not a "sawing" left to right, but a wheel bouncing up and down kinda shake. I wondered that since the shuddering didn't change with RPM then it would be output related. I suppose clutch packs being shared between 2-4-6 means that it should be happening in 4th (unless buried by long multiplication of the final drive ratio), which it doesn't...

A friend had a 94 Lebaron sedan (sad) that would vibrate on acceleration that turned out to be the transmission. This is why I wondered... BUT!

It makes far more sense that this would be fuel/ECU related.

My next tank of fuel I may just swap it out for some premium fuels (Shell comes to mind - lacking ethanol) to see if that makes it go away. Also I will see if your reset makes any changes, and if either solves the problem we're good to go.

I will have to wait until the spring where the fuel blends change to confirm, but as I fuel up later today I should have something to report...!
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post #9 of 32 (permalink) Old 01-21-2014, 12:23 PM Thread Starter
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Quote:
Originally Posted by beskhu3epnm View Post
Great reply!

In my mind I had pictured the converter lockup maybe not being 100% and giving some kind of pulsating feeling. At it's worst, the shuddering was noticeable by passengers in the vehicle who actually expressed concern something was about to break. It was felt in the steering wheel... not a "sawing" left to right, but a wheel bouncing up and down kinda shake. I wondered that since the shuddering didn't change with RPM then it would be output related. I suppose clutch packs being shared between 2-4-6 means that it should be happening in 4th (unless buried by long multiplication of the final drive ratio), which it doesn't...

A friend had a 94 Lebaron sedan (sad) that would vibrate on acceleration that turned out to be the transmission. This is why I wondered... BUT!

It makes far more sense that this would be fuel/ECU related.

My next tank of fuel I may just swap it out for some premium fuels (Shell comes to mind - lacking ethanol) to see if that makes it go away. Also I will see if your reset makes any changes, and if either solves the problem we're good to go.

I will have to wait until the spring where the fuel blends change to confirm, but as I fuel up later today I should have something to report...!
Well - I pulled the battery last night and the shudder is gone so far - I'll know more during the upcoming week. If it indeed goes away, then comes back later, my mind tells me that it's a learned table issue (programming) that's simply a drivability concern.

On another note, it was -1F this AM here and the car did something that it did the LAST time it was very cold (which was the first experience for the car in below zero temps) - it would downshift two gears when full throttle was reached (i.e. kickdown switch), but would not put out full power. It felt like the car was down 30 horsepower. The transmission was not slipping.

It will repeat this for the first 10 miles of my 20 mile drive, then be fine from that point on and during future cold events.

This tells me that there possibly is another drivability issue in the factory tables with (maybe) cam timing or fueling based on intake temperature. Once it tweaks the learned tables for *something* it will 'know' what to do from that point on. Since I'm in a heated garage (I keep it at 40F), I don't think it's low tranny temperature, but something based on intake air temperature.

This is the first winter the production vehicles have seen, so hopefully a TSB is released. I really wish mine would throw a damn MIL light so that it would store a code and help things along repair/diagnosis wise. I also wish the technician would datalog the thing and send it to Mazda for review. They would see an anomaly pretty quickly.
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post #10 of 32 (permalink) Old 01-22-2014, 04:30 AM
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Quote:
Originally Posted by obsessive View Post
On another note, it was -1F this AM here and the car did something that it did the LAST time it was very cold (which was the first experience for the car in below zero temps) - it would downshift two gears when full throttle was reached (i.e. kickdown switch), but would not put out full power. It felt like the car was down 30 horsepower. The transmission was not slipping.
Was the blue cold engine light still lit? The manual says something about the engine limiting itself while it's cold.

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