No one can fix my car! Whenever I go on a road trip and have my air and cruise control on, and after 4 hours of continuous driving my car goes crazy! It starts to decelerate!
When I drive with no air and no cruise control on - it is fine!
Help!
Ms. Or Mr. Kittiefood, Describe “It starts to decelerate!”, Please.
Does it do this rapidly or does the speed slowly deteriorate ? Does it get knocked out of “cruise” and will it “resume” ?
Please try and give more detail.
CSA
It decelerates rapidly and when I press the gas to go, it won’t do anything, I just hear the engine revving. I had to pull off to the side of the highway and turn the car off and then back on.
It won’t resume at all. It is the strangest thing!
“. . .and when I press on the gas to go, it won’t do anything. I just hear the engine revving.”
Are you saying the engine revs up but the car doesn’t accelerate?
Manual transmission or automatic? How many miles on the car?
Yes that is it exactly.
It’s automatic, but is has the capability to be manual if I put it into “sport”.
The shifters are on the steering wheel (which is horribly designed, because you
can accidentally press them). The car only has 50,000 miles on it.
Does the “Check Engine” light ever come on when this happens?
The fact that you can rev the engine with no acceleration makes me think it’s a transmission issue, as if the transmission has suddenly shifted into neutral.
Can you place the transmission into neutral using the shifter paddles on the steering wheel, or only by selecting “neutral” with the shift lever?
You are in the habit of driving more than 4 hours at a time without stopping to stretch your legs, visit a restroom, or fill up the gas tank? That seems uncomfortable and a little dangerous.
At highway speed, with the AC on, your car will run out of gas after about five hours (10.8 gallon tank x 30-40 mpg). If it were me, I’d just stop for gas sooner.
Hey Wes, That’s It ! That’s The Answer To Almost Any Problem ! I Didn’t Think Of It ! Just Before Something Bad Is About To Happen . . . Stop Doing What You’re Doing ! Brilliant !
Also, that stupid Owner’s Manual should have informed Ms. or Mr. Kittiefood never to drive for 4 hours at a time without going to a bathroom. Besides, nobody should ever go that long without a potty break, right ? This would be a non-issue. 
CSA
I am being mocked by someone hiding behind a screen name. I stand by what I wrote before about comfort and safety.
But on topic, if you (kittiefood), or a passenger, or a loose object bump the shifter forward the transmission will go into neutral and produce exactly the results you describe. It is actually pretty easy to do (I own a 2007 Fit). It has only happened to me once (loose water bottle), and I had forgotten about it until now.
Your mechanics have found nothing wrong with your car I gather. I suspect nothing is wrong with the car. Is it possible you or someone else bumped the shifter? Most people I know shift around quite a bit after sitting in a car for several hours, and it would be easy to bump that shifter while trying to get comfortable.
I agree with mcparadise.
When the engine revs but no acceleration results, that certainly seems to point to a transmission problem. Having this checked sooner, rather than later, is a very good idea. Perhaps it will turn out to be an engine-related driveability problem, rather than a transmission problem, but the sooner it is diagnosed the better-off you and the car will be.
Mr/Ms Kittiefood:
How long is the Powertrain Warranty coverage on this 3 year old car?
If, as I suspect, the Powertrain Warranty runs for 5 years/60k miles…or perhaps longer…the car should be taken to the dealership for evaluation and…hopefully…free repairs under the terms of the Powertrain Warranty.
Have you taken a look at your warranty coverage?
Are you aware that you should not have to pay for ANY repairs to either the engine or transmission during the warranty period? (That depends, of course, on the car having been maintained in accordance with the mfr’s maintenance schedule.)
Don’t wait for a diagnosis from anyone on this forum, simply because the dealership has to go through their own diagnostic protocol, and will ignore any diagnosis that you provide. All you need to do is to describe the symptoms in detail, and…hopefully…demonstrate the problem for the dealership’s service staff. It is up to them to diagnose and repair this problem–gratis. That is what a warranty is for.
Why some people do not even attempt to obtain warranty coverage for repairs on a car is beyond my comprehension.
Mr. Sprinkle, With All Due Respect, Lose The Loose Water Bottle. Although Not Covered In The Owner’s Manual, Drinking Water While Operating A Fit Can Shorten Range, Cause Discomfort, . . .
. . . And Lead To The “Shifting Around Quite A Bit After Sitting In A Car” that you talk about.
I’ll bet you’re right. After four hours of drinking water and no potty breaks, one probably starts that leg jiggling (molars are floating by now) routine and bumps all sorts of levers and widgets.
Mr. Sprinkle, That is probably Ms. or Mr. Kittiefood’s only problem.
CSA