My truck wont idle correctly
When i start my truck up and take my foot off the gas padle it cuts off
My car has 190000 miles.
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
This may be a sign of a failing throttle position sensor. The throttle position sensor (TPS) is a sensor used to monitor 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. I would suggest having a professional from Your Mechanic come to you home to diagnose your throttle control system.
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The measurement provided by the TPS is used by the computer to adjust many parameters of the engine, primarily the amount of fuel delivered. A malfunctioning TPS will cause your engine to run poorly. Generally the engine will idle fine but will have difficulty accelerating.
The easiest way to reset your throttle position sensor is to unhook the negative cable from your battery for up to five minutes or to remove the fuse for your engine control module.
The throttle position sensor reports the position of the gas pedal to the computer in your car (Engine Control Unit). The computer then determines the position of the throttle plate. It also calculates the amount of air flow to the engine and the amount of fuel to be injected for the required ratio of air-fuel mixture.
Oxygen (O2) sensor
An oxygen sensor monitors and analyzes the amount of oxygen in a vehicle`s exhaust system after combustion. A dirty, damaged or malfunctioning O2 sensor (or sensors) affects the air/fuel mixture, causing the engine to idle rough.
At idle is should be zero or a couple of degrees. Press down on the gas pedal very S-L-O-W-L-Y until the throttle is all the way open. You should see the percentage of throttle opening gradually increase to 100 percent at wide open throttle.
Acceleration issues: A bad TPS may cause all sorts of power issues. Your engine may start up but it will have little to no power and it causes it to shut off. On the other hand, it can also cause your car to have spontaneous accelerations even if you didn`t step on the gas.
Throttle position sensors are mounted to the side of the throttle plate and measure the position of the throttle — essentially, how far down the gas pedal is pressed.
When the TPS goes bad, the throttle body may not open and the engine will not be able to run without air. It may cause erratic idling, stalling, and sudden surges of acceleration. The car may not start when the TPS is faulty.
Engine hunting and surging at idle is usually caused by a fuel delivery, air leak, or governor system problem. Cleaning/overhauling the carburettor, adjustment of the governor, and/or changing the air filer may be required.
If an engine is not getting enough fuel (this is called “running lean”), due to fuel pressure (regulated by the fuel pump and regulator), restricted fuel injectors, a vacuum leak or really anything that throws off the fuel mixture going in to the engine, this can cause the surge.
A bad TP sensor creates fluctuations in engine RPMs that can be extremely confusing for the ECU where it may not be able to spray a constant stream of fuel into the cylinders and intermittently increase or decrease the amount.
Without a throttle position sensor, the engine control module wouldn`t be able to accurately time the ignition or monitor the amount of fuel required, which might cause the engine to surge or stall and be exceedingly dangerous for the driver and other road/track users.
Do you have to reset computer after replacing throttle position sensor? After replacing the throttle position sensor in your engine, if the engine light was on and has a pending code, the code should go away. If the code doesn`t, however, then the ECM (engine computer module) will need resetting.
There are a few symptoms that may indicate a dirty throttle body, including reduced fuel economy, loss of power while accelerating and engine stalling. If you notice any of these symptoms, it`s best to have your truck checked out by a qualified mechanic.
Once you have fitted a Throttle Position Sensor, or TPS, you will need to calibrate it from within MEITE. First, be sure you have correctly wired, and assigned the throttle sensor signal input to “TPS Raw” in the Analog Settings.
Increase Throttle Response with Aftermarket Throttle Bodies
More air volume and speed is a surefire way to increase horsepower and throttle response at any given RPM. It is easy to achieve this at high RPM when the engine sucks in substantial amounts of air on its own. But coming off idle is another story.
The ECM sends a 5 volt reference voltage to the TPS which passes through a variable resistor of the sensing circuit. This of course is connected to your throttle pedal. When the 5 volts passes through the resistor of the TPS, the voltage will vary based on the position of the throttle plate.
Disconnect the idle air adjustment valve by locating and disengaging the electronic connector that holds it to the throttle body. Turn the idle screw to adjust the idle—turn the screw to the left to increase the RPM or to the right to lower it.
During movement of a vehicle, the signal delivered to the TPS is in the range of 3.5–4.7 volts; a value range that indicates that the throttle valve is in the open position.
The TPS checks the amount of air/fuel mixture being delivered to the engine, while the throttle body temperature sensor monitors the temperature of the air/fuel mixture and the actual throttle body.
A P0122 code is the generic OBD-II code defined as “Throttle Pedal Position Sensor/Switch (TPS) A Circuit Low Input.” This code relates to the vehicle`s Engine Control Module (ECM) and TPS Sensor Circuit A output voltage and is triggered when the voltage falls below the sensor`s anticipated range.
While there are many different types of throttle sensors, there are only two types of throttle position sensors: switch and potentiometer.
There are two main types of throttle position sensors: potentiometer-based and Hall effect-based.
Because the TP sensor is an input to the control module for various automatic transmission functions (e.g., shift points and torque converter clutch operation), a problem with the sensor can cause transmission performance issues. For example, you might experience harsh or delayed shifting.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
When the truck is rolling with clutch in the truck will idle rough and sometimes dies.
ANSWER : This is a common symptom of the idle air control valve failing. This unit monitors the air intake as it is mixed with fuel prior to entering the motor. When this fails, this will cause a rough idle at low RPM’s. I would recommend having an expert from YourMechanic come to your home to diagnose the rough idle firsthand for an accurate repair.
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I parked my truck for 5-10 mins. Tried to turn it on, now it wont start, called a tow tow truck 15-20mins later my truck turned on
ANSWER : It is very likely that you have a powertrain control module failure. This can happen often on many GM vehicles. I would recommend having the powertrain control module tested and replaced as necessary in order to resolve this issue. After the powertrain control module is replaced, a reflash procedure will be required so that the vehicle can relearn all of its primary engine data. Once the reflash is completed, your vehicle should no longer have this issue.
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High idling, jumping while idling, idle air control valve code
ANSWER : Hi there. This can be caused by the issues that you mentioned or a number of other things. You need to make sure all of the connectors are making good contact. I would then need to know what codes are in the computer to know if this is a circuit issue or not. Most of the time, it is not the circuit but instead a vacuum leak.
If there is a vacuum leak, then the vehicle will act like this and the computer cannot control the idle. Most of the time it is a bad hose or an EGR valve that is stuck open. That is the most common cause for this. I typically remove the EGR to check it to feel the diaphragm on the bottom of it to see if it is moving correctly. If you need to have this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair your car’s idling issue.
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Truck idles poorly, starts jumping
ANSWER : There are numerous potential causes for the symptoms you are having. The first thing that comes to mind is a vacuum leak (unmetered air allowing the engine). Vacuum leaks are noticeable at idle and not under load while accelerating. There are several DIY methods for finding vacuum leaks, but the best method is to use a professional smoke machine. Another potential cause for your issue is a faulty idle air control valve (IAC). The IAC is a stepper motor, used by the engine control module (ECM) to control throttle position. The ECM uses the IAC to control idle speed and prevent stalling. If the IAC is not working properly, the vehicle will not idle well. I suggest you have a trained professional, such as one from YourMechanic, inspect your vehicle firsthand to diagnose your rough idle.
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I had my truck towed on a flat bed tow truck and now it is vibrating really bad and it sounds like my tires are howling
ANSWER : The problem sounds like you have flat spots on the tires in the rear when the tow truck operator dragged and pushed the truck with the transmission locked. I would recommend having a vehicle safety inspection to see if there is tire damage or other possible damage done by the tow truck. Have a mechanic from YourMechanic come and do the inspection and check the problems for you.
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After replacing the power steering pump there was a low idle, idle screw is all out, running rich, and idle speed doesn’t change.
ANSWER : Hi there. The engine has a vacuum leak and is causing the engine to stumble down on the idle. Check all of the vacuum hoses and the brake booster for any leaks. The engine is rich for it’s not burning all of the fuel properly and may also have bad spark plugs. If you need further assistance with engine not adjusting the idle, then seek out a professional, such as one from Your Mechanic, to help you.
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Truck horn is beeping without truck being turned on. Why?
ANSWER : The problem is in the horn pad. The horn pad may be damaged or changes in temperature can cause the contacts to touch in the horn pad causing the horn to beep. you may need to call the company to come and fix it or remove the horn fuse until it is fixed.
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My Check Engine Light is on and my truck does not idle when cold. Do I need a new crankshaft position sensor or is this an ECM or timing chain issue?
ANSWER : Hi there. Your vehicle has an idle air control valve that adjusts the idle via commands by the ECU. What it sounds like you adjusted was the throttle plate position when it was closed and had no adjustment on the actual idle. Adjusting the throttle plate rest position is similar to holding the gas pedal slightly to affect engine RPM. The idle air control valve (IAC) can stick over time and mileage, whether due to contamination buildup or simple wear and tear which will require replacement to correct.
Reset what you adjusted and replace the IAC for the idle concern. For the Check Engine Light, there could be an issue with the wire harness, ECU, or even the reluctor plate for the timing chain. This wheel has several notches, or teeth, with one gap, or wide tooth, that denotes cylinder 1 TDC, and provides the ECU with the position of the crankshaft. The ECU uses this information with a similar sensor for the camshaft, compares the two, and determines the relational position of the firing order, etc.
There should be a 5 volt reference available at the sensor; if not, there could be a break in the wire or the ECU is not sending the voltage. Check the wire harness for an opening or short and repair as necessary. If the harness is ok, I suspect either the reluctor plate has failed, the new sensor is defective, or the ECU has failed internally. I recommend having a certified mechanic, such as one from YourMechanic, assist you with a inspection of why car does not idle, a replacement of the idle air control valve, and a Check Engine Light inspection.
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