I've seen several posts about jerky transmission shifts, but not about the issue I have experienced. This happens at intersections, when I am at a dead stop, and take my foot off the brake. The car jumps forward really fast then jerks to a stop. I estimate it is moving about a foot. It has only happened about 4 times in the first 2500 miles I've had the car, but on one occasion pushed me close to a car passing across and in front of me, which freaked me out. Has anyone else seen this? I'm going to tell the dealer about at my next service, but based on their inability to do anything about the really bad 'cross-wind' cabin noise I experience (way worse than the test drive vehicle I went in; I went back and drove it again to confirm), I'm not holding out much hope they'll fix anything.
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Jerky start when taking foot off break at stops
- Thread starter geekraver
- Start date
Bladecutter
Member
- :
- 2014 Mazda CX-5 Touring
Why are you taking your foot off of the brake pedal when you're stopped at an intersection?
What I bet is happening is that you are on a slight incline, and the hill assist has been activated.
For whatever reason, since you are on a hill, you decide to just let the engine hold the car still with your foot off the brake (you shouldn't do that by the way, it can possibly damage the torque convertor).
What's happening is when the hill assist releases the brake, you car lunges forward.
The solution is to keep you foot on the brake when you're stopped, and remove it when you want to go forward.
I'm not going to recommend anything else, because this is a safety issue that you have caused yourself with your own behavior, and isn't a problem with your car.
BC.
What I bet is happening is that you are on a slight incline, and the hill assist has been activated.
For whatever reason, since you are on a hill, you decide to just let the engine hold the car still with your foot off the brake (you shouldn't do that by the way, it can possibly damage the torque convertor).
What's happening is when the hill assist releases the brake, you car lunges forward.
The solution is to keep you foot on the brake when you're stopped, and remove it when you want to go forward.
I'm not going to recommend anything else, because this is a safety issue that you have caused yourself with your own behavior, and isn't a problem with your car.
BC.
...or perhaps he's just taking his foot off the brake to drift forward a bit... or maybe he's in the process to moving his foot from the brake to the gas pedal...
His MOTIVES for taking his foot off the brake are really irrelevant to his concern. Perhaps he was taking his foot off the break because the car was in park and he wanted to get out, run around the vehicle like a maniac while a traffic light was red, and then jump back in. What does it matter?
Instead of attacking by basically accusing someone of causing a safety issue by their own behavior based solely on guesses, why not either try to be helpful to the concern, or move on?
geekraver, I've never experienced anything like what you are describing (unless it was a poor dual clutch transmission) and I doubt I could be much help with the concern, but perhaps answering some questions will help others to be helpful:
Can you more fully describe the situation this occurs in? Are you on level ground or a slope? If a slope, is it an incline or decline? Is your CX-5 an automatic transmission or manual? When this happens, is the car reving (high RPM's) higher than normal at a full stop?
I've heard of similar things when a car has dirt in the fuel line and is trying to compensate, but if that were the case, you'd have other symptoms (and more jerkiness than just coming out of a full stop.)
Gary
His MOTIVES for taking his foot off the brake are really irrelevant to his concern. Perhaps he was taking his foot off the break because the car was in park and he wanted to get out, run around the vehicle like a maniac while a traffic light was red, and then jump back in. What does it matter?
Instead of attacking by basically accusing someone of causing a safety issue by their own behavior based solely on guesses, why not either try to be helpful to the concern, or move on?
geekraver, I've never experienced anything like what you are describing (unless it was a poor dual clutch transmission) and I doubt I could be much help with the concern, but perhaps answering some questions will help others to be helpful:
Can you more fully describe the situation this occurs in? Are you on level ground or a slope? If a slope, is it an incline or decline? Is your CX-5 an automatic transmission or manual? When this happens, is the car reving (high RPM's) higher than normal at a full stop?
I've heard of similar things when a car has dirt in the fuel line and is trying to compensate, but if that were the case, you'd have other symptoms (and more jerkiness than just coming out of a full stop.)
Gary
Yes, gary, you are correct - this is when I am in the process of moving my foot from the brake to the gas. The time it spooked me I did that as the last car was passing me in cross traffic, as it was a busy road with few opportunities (I was turning left) and I needed to take the gap - so having the car do that was not a good thing.
I think I have been on an incline, although in the case described above it was very slight; I was at the top of the hill at that point but there may have been a very slight slope still. The other occasions were, IIRC, situations in which I was facing uphill. So I do suspect the hill assist. But I can feel the hill assist at other times behaving as it should; this jerk is definitely not right.
This is an automatic transmission. When it happened the revs shot up, the car jerked forward, and then the brake slammed on. I don't recall if I had actually touched the gas yet or if I had just stopped pressing on the brake.
A dirty fuel line seems unlikely; this car is very new (about 2000 miles right now), and the first time it happened was about 3 weeks after I purchased it.
I think I have been on an incline, although in the case described above it was very slight; I was at the top of the hill at that point but there may have been a very slight slope still. The other occasions were, IIRC, situations in which I was facing uphill. So I do suspect the hill assist. But I can feel the hill assist at other times behaving as it should; this jerk is definitely not right.
This is an automatic transmission. When it happened the revs shot up, the car jerked forward, and then the brake slammed on. I don't recall if I had actually touched the gas yet or if I had just stopped pressing on the brake.
A dirty fuel line seems unlikely; this car is very new (about 2000 miles right now), and the first time it happened was about 3 weeks after I purchased it.
Oh, and Bladecutter, just to be clear, I only take my foot off the brake when I want to move forward; I'm not relying on the hill assist to stop the car from rolling when stationary. So this is a problem with the car, and not with my driving, which happens to be very safe (no incidents or citations in 30+ years).
Oh, and Bladecutter, just to be clear, I only take my foot off the brake when I want to move forward; I'm not relying on the hill assist to stop the car from rolling when stationary. So this is a problem with the car, and not with my driving, which happens to be very safe (no incidents or citations in 30+ years).
Wow! I find the CX-5 to be predictable in the extreme in such circumstances and very easy to drive. I really like the smooth but direct feeling of the transmission.
Maybe yours is defective.
I'd seriously suggest that you take your car to a mazda service center. Even if they can't repeat the issue, make sure you get a repair order that describes the problem, shows the mileage on the car, etc. It's okay if the repair order says that they can't repeat the issue.... The car might have generated a DTC (diagnostic trouble code) internally when the jumping occurred and they'll be able to see that.
The remainder of this message is the result of paranoia generated by my last vehicle, a 2013 Ford Focus, Lemonade trim:
Even if they can't repeat and there's no DTC, you'll have a record of making the complaint. That might be useful if the problem re-occurs or becomes more frequent. It'll also be priceless if the problem starts to occur very frequently after the car goes out of warranty (as you'll have record of the problem starting while the car was still in warranty.)
It would also be useful if they are unable to repair the problem, it becomes worse, and/or you decide to pursue any type of "lemon law" claim. While I doubt this would come to that, I'm paranoid after my last car...
Good luck
Gary
The remainder of this message is the result of paranoia generated by my last vehicle, a 2013 Ford Focus, Lemonade trim:
Even if they can't repeat and there's no DTC, you'll have a record of making the complaint. That might be useful if the problem re-occurs or becomes more frequent. It'll also be priceless if the problem starts to occur very frequently after the car goes out of warranty (as you'll have record of the problem starting while the car was still in warranty.)
It would also be useful if they are unable to repair the problem, it becomes worse, and/or you decide to pursue any type of "lemon law" claim. While I doubt this would come to that, I'm paranoid after my last car...
Good luck
Gary
deepfriedsushi
Member
- :
- 95 Miata, 14 CX5 Touring FWD, 18 CX9 GT FWD
So the car jumps forward and stops/brakes itself when you let off the gas?
Do you have the Smart City Brake Support System? Does this happen when you let off the gas to let the car go forward, but you have an object (car) in front of you? Maybe the car passing in front of you when you let off the gas triggered the SCBS.
If you have an object in front of you when you let off the gas, the SCBS could be detecting that you have something in front of you and applies the brakes to prevent the accident. Be sure the sensors for the SCBS at the top of the windshield behind the rear view mirror aren't blocked by debris or bird poop, because it could interfere with how the SCBS operates.
SCBS in action.
I can't really think of any other reason why the car should automatically activate the brakes on you, unless something is defective, which is when you should report it to the dealer asap.
Do you have the Smart City Brake Support System? Does this happen when you let off the gas to let the car go forward, but you have an object (car) in front of you? Maybe the car passing in front of you when you let off the gas triggered the SCBS.
If you have an object in front of you when you let off the gas, the SCBS could be detecting that you have something in front of you and applies the brakes to prevent the accident. Be sure the sensors for the SCBS at the top of the windshield behind the rear view mirror aren't blocked by debris or bird poop, because it could interfere with how the SCBS operates.
SCBS in action.
I can't really think of any other reason why the car should automatically activate the brakes on you, unless something is defective, which is when you should report it to the dealer asap.
If you put the transmission in manual mode and click it to 2nd gear two times at a stop the transmission won't shift to 1 st. This could be useful in preventing the car from lurching forward if in fact that is what's really happening. Of course the best thing to do is take it to a reputable Mazda dealer and have them go through the car.
Does this happen when the AC is on or off?
Does it happen when the engine is cold or hot?
What is the idle RPM when in gear and what does it jump to when you move your foot off the brake?
Do you have any non factory floor mats or unsecured factory floor mats?
Do you drive with unusually large footwear?
Does the gas pedal spring back normally and is that area clean?
Does this happen when the AC is on or off?
Does it happen when the engine is cold or hot?
What is the idle RPM when in gear and what does it jump to when you move your foot off the brake?
Do you have any non factory floor mats or unsecured factory floor mats?
Do you drive with unusually large footwear?
Does the gas pedal spring back normally and is that area clean?
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