Skyactiv downshifting surging?

[melly]

It also happened to me within the first few weeks of owning the car. At first I thought I was doing something weird, like giving it too much gas when I downshifted, but since I couldn't make it happen on my own, even when I tried to do exactly that, that seemed unlikely. When I described the problem to my husband (we share the car), he said the same thing had been happening to him.

It is a rather hard thing to describe, so I didn't have any luck finding this problem listed on the forums until now. I did describe it to my cousin who has a 2012 Mazda Speed 3, and he said the problem has never happened to him.

Also, regarding the PCM and adjusting the driving pattern to maintain fuel economy - this explanation seems unlikely, as I am not sure how a surge of acceleration (when you didn't ask for it) would increase fuel economy, as acceleration is the worst thing for fuel economy! Anyone else?

[CajuCLC]

I have had same "problem" when using cars that have "eco-friendly-savegas-engines".
It happened on different cars, different brands, so never bothered to know the cause. lol

[My spoon is too big]

Happened twice today. Both times I was slowing down in forth and at about 20ish mph, I put it in third, had my foot barely on the gas. The first time, the rpms shot up to about 3500 as I didn't have the clutch all the way out. The second time, it accelerated like throttle was at least half way pressed. Both times, when I took my foot off the gas, there was barely any travel left in the pedal. Oh yeah, AC was on max and fan was on 2.

[squigglyquiggly]

Thanks for the AC info. BTW, where was the air blowing (vents, floor, windshield). I am assuming vents, but just to be sure....

Not sure why Mazda Canada and my local dealer are so focused on where as well.

[My spoon is too big]

Just dash vents

[tmart]

I just bought a skyactiv MT yesterday and I'm about to pick it up tomorrow, but I've read the manual already. Could what you guys are experiencing be the DCS system in action?

Dynamic Stability Control(DSC)

The Dynamic Stability Control (DSC)
automatically controls braking and engine
torque in conjunction with systems such
as ABS and TCS to help control side slip
when driving on slippery surfaces, or
during sudden or evasive ma

[melly]

tmart - I wondered this also, but it seems that DSC is meant to do things to prevent sliding, such as apply brakes where needed and reduce torque when needed, so it seems strange that DSC would give you an unexpected burst of acceleration while downshifting. Thoughts?

[zod]

Joining the club here. My Mazada 3 i touring MT 6 does the random surge on downshift as well. Have about 8,000 miles on it. It's done it since we've had it. Happens for both me and my wife.

Took it into the dealer and took one of the mechanics on test drive. I was lucky enough to get the car to surge once on a 20 minute drive. Mechanic didn't seem very interested.

They checked out the car and upgraded the computer firmware and claimed it was was "working as designed". They thought the car was trying to match engine revs to current speed to aid in shifting. Car does this a few times per week still.

I told them that there is never an occasion for a car to accelerate when the driver didn't ask for acceleration. Completely ludicrous. Clearly there's some corner case here where the computer gets it wrong or there somethings not adjust properly. I cant imagine that ALL these cars have this problem.

I'm especially annoyed because we bought this car to have a safe car to teach my kids to drive with.

WATCH OUT FOR RANDOM ACCELERATION KIDS!

Very annoyed.

[Tomato88]

Originally Posted by tmart

I just bought a skyactiv MT yesterday and I'm about to pick it up tomorrow, but I've read the manual already. Could what you guys are experiencing be the DCS system in action?

The most longest DCS trigger I had was when I peeled off on a rainy day at a traffic light. It immediately started stuttering (not shutting) the throttle to gain back traction. I also once triggered it briefly on-ramp when I tried to accelerate rapidly before merging.

[squigglyquiggly]

It happened again to me twice in the last week.

Both times, the A/C was off.

Curiosity....... The last time, I noticed it happened just after I fueled up. I have never noted this connection before. Not even sure there is a connection, just one more thing I noted this time. Initially when it first started happening a few times / week, it definitely was not related as I don't fuel up that much.

I agree with Zod, on the safety issue.