2012 Mazda5 with Hard Shifting (4th -> 3rd)

[t60z]

Hey all, so I have a 2012 Mazda 5 (Automatic) and it's my wife's daily to shuttle the kids around. For the past 2 years we've had this weird issue when accelerating. Specifically, when driving around 40 mph the car is in 4th gear, but if I open the throttle the car hesitates for a split second, the car jerks (feels like the engine is jumping out) then the car speeds up in 3rd gear.

The car has 110k on the odometer, and all maintenance is complete (filters, oil change etc..).

Since the problem came up, I've:

Changed the transmission fluid (no change)
Changed spark plugs (no change)
Changed ignition wires (no change)
Changed battery (was due anyway, but no change to driving)
No check engine light, and there aren't any active codes coming up nor pending ones.

I suspect carbon buildup (not sure how..) because:
My car had trouble starting and after cleaning out the throttle body and replacing the MAF sensor the car started right up with no issues. Look how dirty the throttle body was! [pic]

I poured in Techron concentrate on the last two fill ups. The first one didn't really do much (10oz?) but the second one (20oz) seems to have calmed the issue. There is a slight jerk you can feel in the pedal but not as a passenger if that makes sense. Both times I poured it in when the tank was empty and right before filling up with some more Chevron gas. I gave it a spirited drive immediately afterwards for 20-30 miles (not high speed, just high RPMs on all gears).

I might try another bottle just to be 100% certain.

The only other thing I can think of is there is some mix setting in the ECU or whatever that's stuck and isn't adjusting. I thought I reset the ECU already when the battery was out, but could there be some other procedure I'm missing? What's weird is the problem almost always happens in 4th to 3rd gear. None of the other gears have this problem. I guess it could also be the transmission control module (TCM) but I haven't heard about issues on the 5 with this, just the 3.

FWIW I took the car in to the dealer for the serpentine belt and they didn't see any issues with the car. Should I just take it back to them and show them on a drive? My only worry is there could be something super easy that I haven't thought of and paying through the nose.

My wife drives it most of the time and she has a light foot anyway, so she never runs into this issue. Maybe I just drive it too hard?

 

[alawat82]

Does it still do the hard shift when you're in manu-matic mode and tell it go from 4th to 3rd?
I think you're on the right track with some kind of buildup, that throttle body looked really bad. Have you also cleaned out your MAF sensor?
Make sure all your motor mounts and transmission mount are solid. They seem to be a common failure point and would definitely make a hard shift feel worse.

 

[negusm]

I agree, on checking the motor/transmission mounts.

Based on the description of the symptoms, I'm not feeling that it's anything engine related.

Transmission or mechanical.

 

[Agent]

I'm almost 100% certain that you have a transmission issue. Nobody else seems to ever have trouble with their transmissions, but my 2012 does the same thing. If you step on the gas on a hill or to pass someone, it lags and then BAM!!!! into third gear. It has done it since 70,000 miles. Now I've got 160,000 miles on it.

So far I've changed:
-battery
-trans fluid (Mazda and Transmax)
-trans solenoids
-motor mounts
-transmission mounts

After 90K miles, I just learned to live with it. I have seen that the servo bore can get deformed on this transmission and cause a problem. There is a steel piston that passes through an aluminum cylinder and once it's out of round, it can allow transmission fluid to leak past. I haven't tried to fix that yet, but it's on my radar. It is something that you can do yourself, but good luck finding the kit to do it. If you do, they're expensive.

If I have to downshift, I pop it over to the manual mode and downshift to third with my foot OFF the gas. I then wait the 2-3 seconds for the transmission to shift down and then hit the gas. It is frustrating, but I can't really do anything about it right now.

I'm sorry that your transmission is awful too, but I'm glad that I'm not the only person that has to live with this.

 

[t60z]

I'm almost 100% certain that you have a transmission issue. Nobody else seems to ever have trouble with their transmissions, but my 2012 does the same thing. If you step on the gas on a hill or to pass someone, it lags and then BAM!!!! into third gear. It has done it since 70,000 miles. Now I've got 160,000 miles on it.

So far I've changed:
-battery
-trans fluid (Mazda and Transmax)
-trans solenoids
-motor mounts
-transmission mounts

After 90K miles, I just learned to live with it. I have seen that the servo bore can get deformed on this transmission and cause a problem. There is a steel piston that passes through an aluminum cylinder and once it's out of round, it can allow transmission fluid to leak past. I haven't tried to fix that yet, but it's on my radar. It is something that you can do yourself, but good luck finding the kit to do it. If you do, they're expensive.

If I have to downshift, I pop it over to the manual mode and downshift to third with my foot OFF the gas. I then wait the 2-3 seconds for the transmission to shift down and then hit the gas. It is frustrating, but I can't really do anything about it right now.

I'm sorry that your transmission is awful too, but I'm glad that I'm not the only person that has to live with this.

Ha, thanks (I think!). I'll probably do the same and just live with it. I've got 110k on the ODO and got new tires last year. I can't in full confidence sell it to someone, and I also don't think it's worth repairing (car is worth 7k, and I'd probably spend 2-3k fixing it). My wife usually drives it with a light foot anyway. I figure if it lasts another 2 years it'll be a decade old and I can get rid of it in good conscience.

 

[t60z]

Old thread, but bumping in case it helps someone else.

I did a bunch of research and saw that the TCM (Transmission Control Module) is right above the transmission which gets hot. You usually only have to replace this if you get codes, which I wasn't. I took it out for an hour to reset and reposition on some hard brake lines with zip ties so it doesn't get hot anymore.

I noticed my spark plugs were bad, and two of the ignition coils were bad, so I replaced those.

I drove around and instantly noticed the transmission was way smoother. After a few hundred miles of driving I think this is resolved. It looks like this issue manifests as a transmission issue, but it's actually misfiring related. Because of the misfires, the TCM has to keep readjusting to it, requiring a reset to clear out the system.

The misfires didn't cause any codes to pop up which was strange. I think the car just isn't that sensitive to it. I've actually never had codes pop up on this car, even when the MAF sensor was crazy dirty causing it not to start.