Hello! This is my first post on this forum, I hope y'all can offer some advice.

Car in question is a 2013 Mazda3 iSport Automatic w/ 1500 miles, bought April 15.

Approx. 2.5 weeks after having the car, when it had ~800 miles on it, I was stopped in traffic at a red light and the engine stalled. The check engine light came on as well. I turned it back on and it started normally and the CEL went off.

Brought it to the dealership 2 days after that, where they could not find any codes nor could they reproduce the issue, so they sent me on my way.

Since then on more than 3 occasions, the engine has started to surge when stopped or coasting in 1st gear. Once in a drive thru, once when coasting up to a stop sign in stop/go traffic, once right after starting the car in a parking lot...and so on. I live in TX, so for all of these occurrences it has been 90+ degrees outside.

I took it back to the dealer one other time since then because they thought that a TSB from 2012 could have applied to my vehicle, but apparently it did not and after 4 hours they couldn't figure out anything again.

I dropped it off yesterday (this is visit #3 in < 2 months of ownership..not cool) for them to drive it around for a few days to get more data to send to Mazda and hopefully actually diagnose something.

What could possibly be wrong with my car??

 

Oh, the joys of a new car!

Obviously, I have no experience with the 2013 mazda 3. Look at my vehicles in the signature.
What you describe would make me look at the Idle Air Control Valve or IAC motor or whatever they call it now. This thing should be managed by the computer but it may not work correctly because of a manufacturing defect or dirt or a bad connector.

What kind a nd brand of fuel do you use?

That dealer's service department seems to completely rely on computer diagnostics and TSB's. I prefer techs who also use the gray matter between the ears...

 

I have dealt with a few of the newer models that have have similar weird issues. When talking to mazda tech line they had me start with a soft reset of the PCM which is just disconnecting the battery for 5 min. And then driving the car to relearn shift points on the transmission. Sometimes when u buy a new car the computer learns some weird data from the plant to the boat then to the port and eventually the dealership. Where it was never properly taught correctly. So I would say it just needs rebooted and driven.

 

Thanks y'all, here's a quick update, I don't have complete details since I don't have the car back yet:

It has been w/ the dealer since Saturday. They still couldn't reproduce the issues and the computer hadn't logged any errors/codes, but they have had complaints from others about similar things, and their cars had logged errors. They replaced a valve (Idle Air Control valve I assume).

Then they basically gave it a brain transplant (replaced the computer) because since it had said everything was fine and it obviously wasn't, they figured the computer itself was defective.

After putting in the new computer, it showed another error with the oil pump not sending enough oil to some parts of the engine. Mazda is having them replace the oil pump (which won't arrive til Monday) and then they have to drive/test everything again.

But at least they don't think I'm a liar anymore :P

 

Your car is possessed!

 

"They replaced a valve (Idle Air Control valve I assume)."

In that case my hunch was right on the money.
An oil pump failure in a brand new car would be unusual, not impossible but highly unusual. It is more likely that the oil pressure sensor circuit was malfunctioning.
At least they took it serious.

The whole thing is not a confidence inspiring situation. Keep track of all the paperwork and have a look at your state's lemon laws so you are prepared in case another problem occurs.

 

After 12 days, a new ECM that recorded the right error (P0015), a new oil pump and OCV valve, all seems well again. There is also a TSB for rough idle (01-003/13) that applies to 2.0L 3s and the CX-5.

I got it back today, and could immediately tell a positive change in the way it drives and idles...so now I hope I can just enjoy driving it again

 

A new ECM, told you your car was possessed!
LOL