2013 CX-5 GT, the other night we started up a steep grade, after about 100 feet the car started slowing drastically, it was evident that the tranny had not downshifted, continued up the hill at about 5 MPH (as good as it would go), at the top of the hill where the road leveled out, the car picked up speed as usual, and the car seems to be missing. This is the 2nd time this has happened, had the same problem a couple months ago, the dealer couldn't replicate the problem (in 10 days and 85 miles), and when they finally returned the car they said it was a loose battery terminal. When this happens, lots of dash warning lights come on (check engine, TPS, etc.) Anyone else having something like this?

 

Two questions: What kind of ambient air temps were you driving in during these incidents? Have you had your ECU reflashed under the recall notice that notice that went out earlier this year. It deals with engine misfires under open throttle operation (ie: passing) in temps of 32 degrees or less. ECU mistakenly registers an engine misfire and goes into limp-home-mode which causes engine malfunction much as you describe. In any case, dealer should be able to read error code(s) caused by such events. Sounds like you need to change dealers.

 

The air temps were around 32 degrees, but when the same problem happened a few months ago it was definately above this temp. No recall for the ECM ever has happened. When the problem happened last, the service mgr. said he couldn't read any code(s), that none were stored in the computer, which I couldn't understand. If my GM truck has a misfire for 5 seconds, it will record a code until erased.

 

Plug your VIN into this Mazda recall search engine https://www.mazdausa.com/owners/recalls
and you'll come up with emission recall 8915K titled
"lack of power during hard acceleration in cold weather"

 

The car was taken to the dealer we bought it from, for the 4th time within 6 months for the same problem, and it was diagnosed as a defective coil. The dealer said the coil was to be replaced under the extended warranty, minus the $100 co-pay, and he also wants to replace the spark plugs "because they are due", to the tune of $320. I told him OK for the coil, I'll do the plugs.