2012 Mazda5 nearly stalls under light acceleration
 

When accelerating form a slow speed (coasting), the vehicle hesitates and nearly stalls. While further pressing the accelerator the vehicle very slowly gains speed. This happens randomly, whether the engine is cold or hot on flat or sloping roads. I have never experienced this at highway speeds. The vehilce is new (Odometer 2,100 km). Although, it happens randomly, it occurs at least once on every city excursion.
I had it at the dealer, but they could not repeat the problem and they said there were no other incident reports.
The problem is annoying and actually dangerous, as it occurs when changing lanes (from a slow moving or stationary lane into a fast moving lane). I have had a similar problem with my previous 2007 Mazda5. However, that was fixed at the Mazda dealer by updating the engine control firmware. Has anyone else experienced this problem with the 2012 model?
Thanks,

Mazda5 dead accelerator
 

I too have a new 2012 Mazda5 (now with 4,000 miles) and it often refuses to accelerate when pulling into traffic. If Mazda does not get this solved, they will cause some serious accidents.

My dealer basically blew me off on this.

If I hold the brake, barely on with the car rolling forward, the accelerator can be pushed all the way to the floor with no response.

I think you'll find that's a design feature to stop you accelerating if you accidentally hit the accelerator whilst braking in an emergency. Try taking your foot off the brake.

Once dead - stays dead
 

I see that Nick C is a senior member and as such may be the moderator for Mazda, if so, Nick - this "design feature" is going to kill some customers as they try to make an entry into traffic.

When I push on the accelerator I expect the engine RPMs to increase.

In this case, in order to re-awaken the accelerator one has to pump the accelerator. This reminds me of some of my earlier discussions with Ford (the exploding as tank trick) and GM (our cam shafts are not soft). In each case it required that I just let the problem get bad enough and the manufacturer get enough bad press and finally they will fix the problem, perhaps under pressure from DOT, but they fix it. Mazda will ultimately have to do a service bulletin and issue a recall.

I'll try not to have an accident in the meantime.

Nick is not a moderator, just a regular member like you and me; if he was a moderator there would be something like "Moderator" or even "Super Moderator" below his user ID.

Regarding the brake cut-off for the throttle, many (most? all?) manufacturers these days are playing with the electronic throttle linkages to prevent unintended acceleration. Like it or not, you should never be pressing the brake pedal (even a little) when using the throttle.

No, I'm not a moderator but just an independent, self employed mechanic who specialises in servicing, air conditioning and diagnostics. As Shipo says many manufacturers have devices to prevent the engine revving up if the brake is pressed. There are no circumstances why the brake pedal should be pressed while pressing the accelerator. I'm not suggesting you don't have a problem with your car, but you did state that it wouldn't rev with the brake pedal pressed and I was just telling you why.
The ECU knows the brake is pressed by the activation of the brake light switch. If you have the bad habit of resting your left foot on the brake pedal while pulling away it might be possible to adjust the switch so it's not as sensitive, but it might be better just not pressing the brake.

I've had this car (2012 Mazda 5) for about two weeks now and haven't experienced this issue which is good so thinking maybe it's not a mechanical issue. Sounds like it may be a software issue? Ask the dealer what version of ECU program is currently running or better yet, get one of those ODB-II readers such as ScanGauge II or ScanGaugeE and monitor to see if it shows any error codes while driving. It sounds like the air/fuel is either running too lean or too rich. I've installed on mine, a ScanGaugeE just recently and it gives me vital statistics in almost realtime.

There is no interlock between throttle and brake
 

I checked out the suggestion made that there is some sort of and interlock between the brake pedal and the accelerator. This is not the case as I can accelerate with the brake applied and get plenty of torque.
Hence, that comment was either related to another car or model. I have been checking with the dealer several times whether or not the Mazda factory has put out a technical bulletin on this issue, but nothing yet. I believe that is must be a firmware problem in the engine control system. I have had a similar problem with the Mazda5-2007 model. Mazda fixed it with a firmware update.

Amazing, but not surprising as cars are now more depended upon controller/CPU to do monitor everything from door opening to throttle position.

Just to add to this dilemma you've experienced, let me tell you my similar experience. On Summer of 2007, we bought a brand new Honda Odyssey Touring. As soon as we took it out onto the highway, it would shudder but only at around 35-50MPH. We then moved to a town about 60miles away and never got around to going back to the original dealer to have them take a look.

I then took the car in for warranty repair at a local Honda dealer from where we lived and they've said nothing was wrong. Then a year went by and we get this letter from Honda America that they have a transmission shudder issue -bam! So I call up my local Honda dealer to make an appointment to reflash the ECU to correct it and they said I had to wait several months.

Needless to say, I drove more than 60miles to the dealer I purchased the vehicle from and got it re-flashed the next day. Problem disappeared like magic.

From that day on, I vow not to ever by Honda vehicles again.

I don't know for sure that this is the case but as Pat_in_MN was unable to rev the engine while the brake pedal was being pressed I put this forward as an explanation. Other manufacturers certainly use this as a safety feature. It might be a feature with the automatic transmission though?