RPM running high in neutral

ANSWER : The problem may be the transmission pilot bearing for the transmission input shaft on the back of the crankshaft seizing up or the input shaft on the transmission seizing. If it is not the transmission, then it is the internal engine camshaft or crankshaft seizing up and rocking the engine with the transmission loosening the seized bearing. Have a mechanic listen to the noise and verify what is failing in the engine or transmission in order to diagnose the car’s starting problem.

ANSWER : Hi There,
There are 3 sources of signals that are involved in up and down shifting points the computer arrives at to direct transmission shifting.

The Idle Air Control Valve. The idle air control valve is a small valve on the engine’s intake system that reads the air intake as it comes into the motor. This is controlled by the car’s ECM which uses this information to make adjustments to the air/fuel ratio depending on various inputs such as outside air temperature, intake air temperature, load and various other things. As you accelerate, your car’s engine is receiving a much higher dose of fuel than when at idle and conversely, when you let off the gas pedal, there is a sudden change in this fuel supply as a result of your foot letting off the pedal.
The Throttle Position Sensor. The throttle position sensor monitors the throttle position of the throttle plate inside the throttle body in relation to your foot position on the gas pedal. Based upon the inputs from the sensor reading your foot’s position on the pedal, the ECU then makes the direction to supply more or less fuel to the motor. When this sensor is not working properly, this can cause intermittent responses when pressing the gas pedal.
VSS speed sensing. The transmission speed sensor is a magnetic sensor that provides this information, allowing the transmission to shift smoothly. The sensor counts the internal number of revolutions of the transmission and transmits that information to the transmission control unit, where the data is used to determine the rotational speed. As the rotation increases, the control unit directs the changing of gears. When this is not working properly, this may cause the transmission to shift erratically or in some cases not at all.

I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your vehicle to determine what may be causing this.

ANSWER : Knowing the results of the computer diagnosis as well as the part that was replaced can be helpful in assisting you with your Pontiac G3. It is possible the part that was replaced is defective and may need to be replaced. Based on what you described with your vehicle, it appears that you may be experiencing transmission issues.

The engine should never be revved up to six to seven thousand RPMs when the vehicle is not moving, as this can cause damage to the vehicle’s components. Because the information provided is a little unclear, it is hard to determine if you are having concerns with your transmission or if the problem lies with the engine itself.

If you don’t trust going back to the same mechanic that worked on your car originally, get yourself a second opinion and enlist the help of one of our certified mechanics who can diagnose why the Check Engine Light is on as well as determine why your Pontiac is not accelerating. They will also be able to assist you with the repairs needed to get your G3 up and running again.

ANSWER : This may be a sign of a faulty MAP sensor as the vehicle responds adversely to a load put on the motor (i.e. putting it in gear, turning on AC or engaging the brakes). The Manifold Absolute Pressure (MAP) sensor senses engine load and generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment. When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine takes in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the MAP sensor, it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power. The computer will then retard (back off) ignition timing slightly to prevent detonation that can damage the engine and decrease performance. This may also be caused by other closely related components such as a dirty or failing mass air-flow sensor, a faulty throttle position sensor or potentially a vacuum leak. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

ANSWER : Hello. The two most common issues that cause this are a bad crank or cam sensor, or a failing throttle body. I usually install a scan tool and see if the sensors are reading right. If they are, then I try cleaning the throttle body to see if it helps. If that does not help, then I check the functionality of the throttle body and replace it if necessary. I have also had the computer fail on this car and cause this, but that is not as common. If you are going to have this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose your shaking and idling issue.

ANSWER : High idle can be caused from several things. Your Saturn’s extremely high idle is likely being caused by air leaking into the intake manifold. It’s called a vacuum leak. This can be caused by a hose that has fallen off or deteriorated with age. An intake manifold gasket can also leak, which allows extra air into the engine. The computer senses the extra air, adds fuel to match, and suddenly you have a high idle speed. A problem with the engine coolant temperature sensor can also lead to fast idle if it’s mistakenly telling the computer that the engine is very cold. There is also a component called the Idle Air Control (IAC) that the computer uses to meter the correct volume of idle air into the intake manifold. The IAC may be dirty, stuck, or broken from old age. A certified mobile mechanic from YourMechanic can visit your home or office to inspect why your vehicle has a high idle and provide any necessary repairs.

ANSWER : Hi There,
What you are describing sounds like possibly a bad speed sensor or potentially a faulty transmission control module, which also controls the speed sensors. The transmission control module has various sensors such as vehicle speed sensors, wheel speed sensors, throttle position sensors, turbine speed sensor, and transmission fluid temperature sensors that all direct information to it in order for it to perform it’s function. Other functions controlled by the TCM are components such as a kick down switch, traction control system, and cruise control module. Any of these may also affect the way the transmission control module performs and controls the transmission and the shifting of your vehicle. A faulty transmission control module may cause also cause a delay in acceleration or erratic shifting of gears. Lastly, this may also be a result of low transmission fluid. I would suggest having a professional from Your Mechanic come to your location to properly diagnose your transmission problem.

ANSWER : Hi there. Assuming your vehicle has ETC (electronic throttle control), "drive-by-wire" problems can develop when cleaning is performed. Manually opening the throttle plate may have affected the close position. An idle relearn performed with a capable scanner may resolve the issue. If the Check Engine Light is on, this may help direct the diagnosis. A vacuum leak may also create a higher than expected idle. I recommend having the vehicle’s high idle diagnosed and repaired by a certified technician, such as one from YourMechanic.