Cruise control turned on, sudden acceleration, high revving
My car has 74,000 miles on it. Recently, I was driving uphill at speed around 56 mph, when the cruise control was activated and the car started accelerating suddenly by itself. At that point, the engine was revving high and the RPM jumped to over 4000. I started to brake and the cruise control turned off. There was a vibration in the steering wheel as well. Also, upon applying the emergency brake, it suddenly went to the floor and was completely unresonsive. I managed to bring the car to a halt. The dealer couldn't find the problem and said the car requires further inspection. Do you have
Experienced mechanics share their insights in answering this question :
Hey there. This could be from a defective cruise control switch shorted or a problem with the throttle control actuator. The vehicle should be towed to the dealer and left there until they verify and repair the problem. The dealer will not repair something unless they can duplicate the problem. Without duplicating the issue it cannot be diagnosed. Check to make sure your floor covers are secure away from the pedal. If you would like to have an outside expert give the car a second opinion, a qualified professional from YourMechanic can come to your car’s location to inspect the acceleration, cruise control, and vibration issues.
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This could be from a defective cruise control switch shorted or a problem with the throttle control actuator. The vehicle should be towed to the dealer and left there until they verify and repair the problem. The dealer will not repair something unless they can duplicate the problem.
The cruise control system will be reset to the speed you are travelling when you release the knob. For a quick reset, accelerate with the accelerator pedal to the desired speed, then press and release the “SET/COAST” button.
Ultimately, the biggest advantage of using cruise control is its ability to lessen the feeling of fatigue of the driver during long-distance driving, while maintaining fuel-efficiency by eliminating unnecessary acceleration and deceleration.
Speed surges while cruise control is engaged
If the cruise control vacuum reservoir fails, the cruise control system will be left without the vacuum it requires to hold the vehicle at a steady speed or rate of acceleration.
RPM fluctuation is a common issue for cars with faulty spark plugs as they fire the fuel with the pistons. If they wear out, your acceleration slows, and jerking and misfire start occurring, which, in combination, causes poor fuel economy and vibrations.
When the transmission develops a leak and fluid levels fall, a vehicle will begin to rev at higher levels as a result of the gearbox band or torque converter slipping. The vehicle may also experience irregular or delayed gear shifting. A manual vehicle experiencing this difficulty may be related to a slipping clutch.
To do this, turn the cruise control off by disengaging the switch in your car. Next, turn the system on again, set a speed, and reapply cruise control. Sometimes resetting the system is all it takes to restore functionality, but if you continue to experience increasing or decreasing speed, you have a problem.
The ECU monitors the speed of the vehicle and makes sure the vehicle gets up to the set speed and stays there. If all of a sudden the vehicle starts climbing a hill and the speed decreases, the ECU will see this and have the actuator pull the cable to open up the throttle and get the vehicle back up to speed.
The speed sensor is the part of the system that determines how fast a car is traveling. Since cruise control requires a precise speed reading, cruise control will not work correctly if the speed sensor is impaired.
The systems of a car are highly interconnected, which means that a seemingly insignificant issue can be an early warning sign for a bigger problem that you shouldn`t ignore. In the case of a faulty cruise control system, it can point to issues with acceleration or even your engine.
Since your car`s cruise control is part of an electrical system, it needs a fuse to function properly. A short circuit in this system can cause a fuse to blow, which means that the cruise control will suddenly stop working. Fortunately, replacing a blown fuse is a cheap and easy repair for any auto mechanic.
A quick way to diagnose this is to try holding the brake pedal up with the top of your left foot at the same time as you are engaging the cruise control while on a test drive. If the cruise control tries to set, then the brake switch will most likely need to be adjusted.
If the RPMs are too high, try dropping it down a gear. This can solve the problem quickly and easily. Depending on what equipment the engine is hooked up to, you may be able to control the RPMs with gears. If the RPMs are too high, try dropping it down a gear.
Worn Transmission Fluid (Automatic Transmission)
Over time, the transmission fluid gathers dirt and grime. This can cause the engine to run roughly, stall or fail to accelerate when you press down on the gas pedal. You may need to have a transmission fluid change before more damage is done.
Most often, over-revving occurs not because of a deliberate attempt to push a vehicle, but rather as a result of missing a gear while shifting. When a manual car accidentally downshifts, a rev limiter will not be able to react quickly enough to prevent the engine from over-revving.
A radar sensor is installed on the car`s front grille, which can sense how close or far away the vehicle in front is. By sensing this distance, the car will “adapt” its cruise control speed to maintain a safe distance from the vehicle ahead.
An electronic control module controls most of today`s cruise control systems. It can be a standalone or integrated into the PCM or BCM. The module uses several inputs to control operation and vehicle speed. These are the components found on most cruise control systems.
The Adaptive Cruise Control camera is located behind the windshield in front of the rearview mirror. It`s important to keep the windshield clean for the camera to work properly. On some vehicles, the feature also uses radar sensors located in the front grille or bumper.
But instead of pressing the accelerator pedal, it uses an actuator to control the throttle and helps your car continue cruising at the same speed. The cruise control system used in older cars is connected to the accelerator through a cable to maintain the gas pedal in a certain position to keep the pre-set speed.
Vehicle Speed Sensor (VSS)
The Vehicle Speed Sensor measures vehicle speed. When it fails the transmission can stop shifting or shift late and harsh. A bad VSS may also inhibit overdrive and the converter clutch.
Uneven or Slow Acceleration
If there`s any dirt or coking on the throttle body this will prevent the car from picking up the power it needs from combustion. What does this feel like behind the wheel? It may be that the car takes longer to get going than usual or the speed picks up in irregular bursts.
Note that a weak battery can randomly knock other features offline, too, including adaptive cruise control, blind spot monitoring, and many more.
An alternator issue, some loose wiring, a battery issue, a fuse or switch issue—could interrupt power to the cruise control and cause it to fail.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
Cruise control turned on, sudden acceleration, high revving
ANSWER : Hey there. This could be from a defective cruise control switch shorted or a problem with the throttle control actuator. The vehicle should be towed to the dealer and left there until they verify and repair the problem. The dealer will not repair something unless they can duplicate the problem. Without duplicating the issue it cannot be diagnosed. Check to make sure your floor covers are secure away from the pedal. If you would like to have an outside expert give the car a second opinion, a qualified professional from YourMechanic can come to your car’s location to inspect the acceleration, cruise control, and vibration issues.
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Cruise control turns on at idle, but when the car reaches 10 mph the cruise turns off and won’t turn back until idle again.
ANSWER : Hi there. Check all of the grounds to the vehicle and see if there is any wires that are damaged from the taillight short. A loose ground will cause multiple problems with the electrical system and some or multiple components will not work. If you need further assistance with your electrical issues, then seek out a professional, such as one from Your Mechanic, to help you.
Read Full Q/A … : Cruise control turned on, sudden acceleration, high revving
Adding cruise control on a factory non equipped car.
ANSWER : The unfortunate truth is the dealer is correct. What you are doing is in theory feasible but not common at all. I haven’t run across anyone who has done what you are doing and I have often wondered how such an endeavor might work. My point here is, I am not surprised the dealer isn’t sure because it’s likely they have never done this themselves. The dealer doesn’t set up the PCM (Powertrain Control Module) in the cars they sell. The manufacturer does and guessing what happened when a car is being built is not common knowledge.
Anytime you modify any car, there are always details such as this that you will possibly have to address. When you choose to modify a car, you are now the engineer. The simple answer is that I can’t tell you with certainty whether or not the PCM in your car has cruise control capability. The only way to find out is to allow the dealer to check in out. Independent shops might possibly be able to, but the equipment they have is aftermarket and not produced by Mazda. The electronic equipment the dealer has is. The dealer equipment will most likely be able to do what you need.
Read Full Q/A … : Cruise control turned on, sudden acceleration, high revving
Having intermittent problems with cruise control on my car
ANSWER : Hello. This can be caused by a number of different issues. Most of the time this is caused by a bad brake switch. If the switch is shorting out, then it will cause the computer to think that the brakes are being applied, which turns off the cruise control. If the switch is fine, then it may have a bad speed sensor or the cruise control switch itself is bad.
One of the easiest tests I do is simply have someone drive behind me and see if the brake lights are coming on without touching the pedal. If it is, then you should replace the switch. If not, then further testing of the circuit has to be done. If you need to have this done, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose your cruise control problem.
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When disabling cruise control, SUV kept accelerating to 115 mph
ANSWER : From your description it sounds like the throttle body became stuck. Since this vehicle does not have a throttle cable it is possible that a sensor malfunctioned and caused the throttle to stay on. These vehicles have been known to break the gears inside the throttle body and cause the symptoms you described. It is possible that the throttle body may need to be cleaned or replaced. Also, in the future, if the throttle sticks the best course of action is to simply turn the ignition off. Don’t turn it all the way back because that would lock the steering wheel. Only turn it back one position to the accessory position.
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PO341 code – cruise control kicks off, engine light and vsa lights go on.
ANSWER : There could be an issue with the cruise control switch and the brake switch. The VSA light refers to the brake system and the light maybe coming on for the brake switch not functioning properly causing the cruise control switch to disengage. The code P0341 refers to the camshaft position sensor, which could be coming on for the sensor malfunctioning. If the camshaft position sensor is not reading properly, then the cruise control will disengage as the engine is not in time correctly. If you need further assistance with your cruise control disengaging on its own, then seek out a professional, such as one from Your Mechanic, to help you.
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Turn Signal, cruise, brakes, and emergency flashers not working properly.
ANSWER : If you have already replaced the flasher module for the turn signals, your problem may be in the switch assembly whether it is a shorted circuit or the contacts in the switch not making a proper connection and causing problems with other circuits. The problem with the brake lights and cruise control may be the brake light switch on the brake pedal. Consider hiring an experienced technician like one from YourMechanic who can come out and take a closer look at your lighting concerns and offer a more personal diagnosis.
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Engine turned off but inside of car still on, now engine won’t turn back on.
ANSWER : Hi there. The symptoms you’re describing with your boyfriend’s 2002 Grand Cherokee appear to be related to a broken or worn out ignition switch or relay. The ignition switch on the inside of the steering column is attached to multiple electronic connections that send signals to a relay box; which in turn, sends the signal to the individual components. The issue could be related to the ignition switch, the relay, or any of the components in between. If you want to have the fault pinpointed in person, I would have this starting issue inspected by a trained professional to ensure that the correct repair is made.
Read Full Q/A … : Cruise control turned on, sudden acceleration, high revving
