I was driving my 2007 Mazda3 on Sunday at about 70 MPH for about 3 hours in 105 degree weather (NoCal to SoCal). The throttle started "surging" (speeding up and slowing down slightly with no change in pedal position). Also, when I pulled over to check things, the brakes felt like there was no power assist.
Had it towed to the dealer where I bought it - they have had it for two days and cannot find anything wrong!
I'm afraid to take it back because of the brake problem I experienced.
Any ideas???
Thanks.

 

electronics stuff is much harder to re-produce and to trace.......btw how do you know for sure the brake is not having the power assist? when you were driving 70MPH, were you using cruise control?
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Easy Vape Vaporizor

 

It just felt like there was no power assist - took a great deal of pressure to stop. This was when I was only going 25-30 MPH, not 70.
Dealer now says they checked with Mazda and they have seen this before and recommended reprogramming the "PCM" or "ECM"? (No codes showed up when they scanned the computer) Dealer claims they have done so and I am to pick-up the vehicle today, even though I have no way of knowing that they actually did reprogram the module or if that will fix anything. This does not give me a warm fuzzy feeling, but I don't see where I have any choice in the matter.
Hopefully I won't rear-end somebody when my brakes fail.

 

Even if you lose brake boost completely you still have brakes. It sounds more likely however that the ABS has gone flaky. You didn't say if the increased pedal pressure was accompanied by a pulsing of the pedal.Either way stopping distance will be increased but it's not likely that your brakes will fail completely.When you get the car back, take it to an empty parking lot or deserted stretch of road and try a couple all-out stops from 40mph or so to see what happens. If there is still a problemcall the Mazda zone office and demand that a zone rep. look at the car.You can't take a chance with brakes.

Dealers will always take the easy way out and do as little as possible so you have to be assertive right off. Remember -don't trust a dealer as far as you can see them. I say that with with 40 years of experience dealing with them and a (thankfully) shorter time working for them.