no fuel while accelerating

Accelerating Issues

Engine Hesitates, Stumbles, Lacks Normal Power

Car accelerate slowly when  gas pedal is depressed

You’re driving along in your vehicle, and everything seems fine – until you start up a hill, or try to quickly pull out into fast-moving traffic. Then it happens… nothing. Sure, the car is moving, but it’s ridiculously slow and you can tell that the engine is struggling to keep up.

This is a common problem found especially in high-mileage vehicles. Before you get too worried, let’s take a look at some of the possible easy fixes….

– The O2 sensor. The oxygen sensor (or O2 sensor) is a device that helps monitor the emissions of your vehicle so as to analyze the air-to-fuel ratio going through the engine In a nutshell, you need to proper amount of oxygen to properly burn the fuel in the engine. Not enough oxygen results in unburn fuel (rich mixture) and too little oxygen (lean mixture) causes more pollutants and can actually damage your engine. When this sensor detects a problem, it sends a signal to the engine to change the amount of fuel being used. If your sensor is malfunctioned, it could be messing up your fuel mixture; and if it’s out altogether, your car’s pretty much just guessing as to what mixture it needs at the moment.

- Fuel filter. Changing the fuel filter (especially if it’s been a while) may be your ticket here. If fuel can’t get into the engine, you’re not going to be getting anywhere very quickly. In addition to this, it’s not a bad idea to get an injector flush altogether.

– Clogged air filter or blocked exhast. Air is a very important part of proper car function (or any type of combustion, for that matter). Make sure your engine’s getting the necessary amount of oxygen it needs to operate.

- Timing belt. If this is off by even 1 tooth, it can cause acceleration problems.

And of course there are many other possibilities –

Fuel pump may need to be replaced
Transmission may need some work
A slipping clutch could be the culprit.

The computer uses this information to determine how much fuel is needed to maintain the correct air/fuel mixture, and when extra fuel is needed if the throttle suddenly opens wide.
Symptoms:
Engine Hesitation
Lacks Power.
Throttle Position Sensor (TPS) full range test
Mass Airflow (MAF) Graph and Fuel Trim Readings
Probable Causes:
Lean Fuel (P0171, P0174)
Throttle Position (P0120 or P0124) or (P0222 or P0229)
An engine that hesitates, stumbles or misfires when accelerating or when it is under load, is an engine that is either sucking too much air, not getting enough fuel, or misfiring. If the Check Engine Light comes on, you may find any of the following codes:

P0171, P0174 Lean fuel condition codes
P0120 to P0124 Throttle position sensor codes
P0222 to P0229 Throttle position sensor codes
P0400 to P0409 EGR related codes
If there are no misfire codes, a common cause of acceleration stumble is a bad throttle position sensor (TPS). The TPS tells the computer how far the throttle is open. The computer uses this information to determine how much fuel is needed to maintain the correct air/fuel mixture and when extra fuel is needed if the throttle suddenly opens wide.

Another common cause are dirty fuel injectors. If varnish deposits have built up in the tips of the injectors, they won’t spray as much fuel as they normally do, or will “dribble” fuel instead of spraying a fine mist. This creates a lean fuel mixture and conditions that are ripe for stumble and hesitation (also misfire). Look at short term fuel trim (STFT) and long term fuel trim (LTFT) with your scantool. If the numbers are high, it tells you the engine is running lean and the injectors need cleaning. Treat mild cases with a high quality fuel-injector cleaner additive. Severe cases require professional cleaning equipment. Other problems that cause acceleration stumble include vacuum leaks, low fuel pressure, a weak spark caused by low coil voltage or bad coil(s), retarded ignition timing, and contaminated gas.

Look at the following with your scantool : throttle position, mass airflow (MAF), short term fuel trim (STFT), long term fuel trim (LTFT), ignition timing, and fuel pressure (if a PID is available). Throttle Position Sensors (TPS) typically wear in the idle and just above idle positions, but they may also have dead spots at any point in their range of travel. With the key on, engine off, graph the sensors output while slowly opening the throttle all the way. The graph should look like a relatively smooth ramp, with no suddenly drops or flat spots.


A seemingly unrelated issue that surprises even the most experienced mechanic
For best results, taking your car to a trusted mechanic for his evaluation my be in your best interest to get to the root of the problem before wearing yourself out trying to address the issue through a costly trial-and-error process – which could result in new problems if not properly handled by someone with proper knowledge and experience.


This Will Help.

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how to replace Throttle position sensor on 2000 ford expedition

Ford TPS Sensor Replacement

Throttle Position Sensor

The Throttle Position (TP) sensor is a potentiometer that provides a signal to the PCM that is directly proportional to the throttle plate position. The TP sensor is mounted on the side of the throttle body and is connected to the throttle plate shaft. The TP sensor monitors throttle plate movement and position, and transmits an appropriate electrical signal to the PCM. These signals are used by the PCM to adjust the air/fuel mixture, spark timing and EGR operation according to engine load at idle, part throttle, or full throttle. The TP sensor is not adjustable.

The TP sensor receives a 5 volt reference signal and a ground circuit from the PCM. A return signal circuit is connected to a wiper that runs on a resistor internally on the sensor. The further the throttle is opened, the wiper moves along the resistor, at wide open throttle, the wiper essentially creates a loop between the reference signal and the signal return returning the full or nearly full 5 volt signal back to the PCM. At idle the signal return should be approximately 0.9 volts.

Removal & Installation

1. Remove the throttle body (TB).
   
   WARNING

   Failure to remove the TP sensor screws in the following manner will result in damage to the screws. First loosen the screws 1-2 full turns using a hand tool and then use a suitable high speed driver to complete the removal.
2. Remove and discard the screws and the TP sensor.
   
   WARNING

   Do not reuse the TP sensor and screws. A new TP sensor and screws must be installed.
   
   
   
   NOTE

   When installing the new TP sensor, make sure that the radial locator tab on the TP sensor is aligned with the radial locator hole on the throttle body.
3. To install, reverse the removal procedure and note the following:
   1. Tighten the new sensor screws to 27 inch. lbs. (3 Nm).

5.4L & 6.8L Engines

1. Disconnect the battery ground cable.
2. Loosen the clamp and position the air cleaner outlet tube aside.
3. Remove the accelerator cable snow shield.
4. To remove the throttle position (TP) sensor.
   1. Disconnect the electrical connector.
   2. Remove the screws.
   3. Remove the TP sensor.
5. To install, reverse the removal procedure.

Testing

Fig. TESTING the TP sensor signal return voltage at idle

Fig. Test the operation of the TP sensor by gently opening the throttle while observing the signal return voltage. The voltage should move smoothly according to the amount the throttle is opened

Fig. TESTING the supply voltage at the TP sensor connector

Fig. The TP sensor can be monitored with an appropriate and Data-stream capable scan tool

1. With the engine OFF and the ignition ON, check the voltage at the signal return circuit of the TP sensor by carefully backprobing the connector using a DVOM.
2. Voltage should be between 0.2 and 1.4 volts at idle.
3. Slowly move the throttle pulley to the wide open throttle (WOT) position and watch the voltage on the DVOM. The voltage should slowly rise to slightly less than 4.8v at Wide Open Throttle (WOT).
4. If no voltage is present, check the wiring harness for supply voltage (5.0v) and ground (0.3v or less), by referring to your corresponding wiring guide. If supply voltage and ground are present, but no output voltage from TP, replace the TP sensor. If supply voltage and ground do not meet specifications, make necessary repairs to the harness or PCM.

Ford F-150/F-250: How to Replace Throttle Position Sensor

A TPS is the throttle position sensor that gives information to the computer of your F-150 or Super Duty on the position of a car's throttle. Your TPS is responsible for checking your engine to ensure fuel efficiency. If you notice your engine light is on, there are difficulties when you change gears, the gas level drops when the tank is full, your car automatically jerks when driving, the engine suddenly stalls, or you feel a surge in speed when on the highway, these are all signs that your TPS needs to be replaced.

Materials

• Paper towel
• Flat head screw driver
• Carb cleaner
• New throttle position sensor

Step 1 - Remove the obstacles

Remove the throttle body cover, then remove throttle body sensor, which is mounted on the front of your mantle fold. Then, take the accelerator cable off using a flat head screw driver by pressing under the part.

• 

  Figure 1. Throttle Body Cover.

• 

  Figure 2. Throttle Body Sensor.

• 

  Figure 3. Accelerator Cable.

Step 2 - Remove the vacuum hose

Figure 4. Remove vacuum hose.

Remove the vacuum hose fitting to access the sensor.

Step 3 - Remove the TPS sensor

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  Figure 5. TPS.

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  Figure 6. TPS.

Make sure to remove the TPS sensor and 2 screws that connect to bottom of throttle body. Once the old sensor is off, replace it with the new one. Clean the throttle body really well, then install it back by reversing the steps above.

Pro Tip

• When taking off the accelerator cable with the screw driver, remove it softly to avoid breaking the clips.
• As a fourth step, you may want to clean the electric part of the valve with carb cleaner.
• Remember to clear the memory of your codes after replacing the TPS.

Testing and troubleshooting the throttle position sensor (TPS) on your Ford or Lincoln car, pick up or SUV is an easy thing to do. You don't even need a scan tool to test it. A simple multimeter will suffice and in this article I'll take you thru' the whole diagnostic process step by step.

Below you'll find a list of Ford and Mercury and Lincoln cars, pick ups and SUV this article applies to (although the tests could apply to any Ford vehicle on the road today). Also in this section you'll find the info to make your testing as easy and as uncomplicated as possible.

OK, one last thing before we jump into the article, you can find a complete list of 4.6L and 5.4L ‘How To Test’ articles that are located in this Web Site and at troubleshootmyvehicle.com and this list is found here: Ford 4.6L, 5.4L Index of Articles.

Symptoms of a BAD Ford TPS

The most common symptom is the CHECK ENGINE LIGHT (CEL) is on (also known as the MIL=Malfunction Indicator Light) on your instrument cluster and annoying the heck out of you as you drive. Among other things, your vehicle might be experiencing:

1. TPS diagnostic trouble codes (DTCs) stored in the vehicle's computer's memory.
   1. P0121: Throttle Position (TP) Circuit Performance Problem.
   2. P0122: Throttle Position (TP) Circuit Low Input.
   3. P0123: Throttle Position (TP) Circuit High Input.
2. Really BAD gas mileage.
3. Transmission does not shift out of second gear.
4. No power as you accelerate the vehicle.
5. Hesitation when you step on the accelerator pedal.

What tools do I need?

As mentioned at the opening of this article... all that you'll need to be able to use the info and perform the tests in this article is a multimeter (don't have a digital multimeter? Need to buy one? Click here to see my recommendations: Buying a Digital Multimeter for Automotive Diagnostic Testing).

You may need a helper to perform some of these tests.

Circuit Descriptions of the Ford TPS

• 
• 

As you already may know, the throttle position sensor (TPS) on your Ford (or Mercury or Lincoln) vehicle has three wires coming out of its connector. Below are short descriptions of the signal each one carries. This are the Circuit Descriptions that we'll be using thru' out the rest of the article to test the TPS on your vehicle.

1. Circuit labeled 1:
   1. 5 Volts from PCM.
2. Circuit labeled 2:
   1. Throttle Position (TP) Signal Circuit.
3. Circuit labeled 3:
   1. Sensor Return (Ground) Circuit.

I recommend that when you test for the particular signal in the wire, that you use a tool to pierce the Wire... such as a Wire-Piercing Probe (click here so that you can see what one looks like: Wire Piercing Probe). Disconnecting and probing the front of the female terminal of the connector can get you into a lot of trouble... if you open up the terminal with the probe you're using.

One last observation... these three circuits go directly to the PCM. So you need to be careful not to short these wires to Power (12 Volts) or you may fry the PCM.

How Does the Ford TPS Work?

Here's some very basic working theory that'll help you to understand the ‘why’ and ‘how’ of the three tests you're gonna' do with the help of this article. OK, in a nutshell.. when you crank and start your Ford vehicle:

1. The PCM (Powertrain Control Module=Fuel Injection Computer) feeds the throttle position sensor with 5 Volts and a Ground.
2. This Ground is known as the Sensor Return in Ford tech speak.
3. As you step on the Accelerator Pedal, the TP sensor translates the amount of throttle plate opening (caused by the accelerator cable) into a voltage signal the PCM can use.
4. The PCM uses this voltage signal , that will vary with the amount the throttle opens as you accelerate or decelerate the vehicle, to inject fuel, control ignition timing, and the rest of the song and dance the Computer has to do to get your vehicle moving or slowing down.

Pretty simple stuff, no? Well testing it is just as simple. Since you'll be working in the engine compartment, no need to tell you (but I'm gonna' tell you anyway) to be alert and be very careful. Use common sense and take all necessary safety precautions. OK, on with the show... go to TEST 1

For Further Part Go To Part 2

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How To Test And Replace Throttle position sensor

FORD TPS SENSOR REPLACEMENT PART 2

TPS TEST 1: Testing the 5 Volt Reference Signal

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The very first test we'll do, is to make sure that the throttle position sensor (TPS) is getting power.

As you already know, this power is in the form of 5 Volts DC and is provided by the PCM.

This test (as all of the tests in this article) must be done with a multimeter, either digital or analog. Also, I recommend that the engine be at its operating temperature... since the heat accumulated by the TPS from the engine may help to find a stubborn glitch in the sensor.

These are the steps:

1. Remove any plastic covers that may be hiding the TPS from view and access.
2. Put your multimeter in Volts DC mode (don't have a digital multimeter? Need to buy one? Click here to see my recommendations: Buying a Digital Multimeter for Automotive Diagnostic Testing).
3. With the RED multimeter lead, and an appropriate tool, probe the circuit labeled with the number 1 in the photo.
4. Connect the BLACK multimeter lead to a good and clean ground point on the engine or directly on the negative battery terminal.
5. Turn the Key to its ON position but do not start the engine.
6. Your multimeter should read 4.5 to 5 Volts.

CASE 1: If the multimeter registered 4.5 to 5 Volts, then the PCM is feeding the appropriate voltage. The next step is to test the Signal Return Circuit, TEST 2: Testing the Sensor Return (Ground) Circuit.

CASE 2: If the multimeter DID NOT register 4.5 to 5 Volts, then the PCM is NOT feeding the appropriate voltage either because there's an open short in the circuit or the PCM is fried. Altho' testing these two conditions are beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) on your Ford vehicle as being the cause of the problem and/or the TPS diagnostic trouble code (DTC) lighting up the check engine light (CEL).

TPS TEST 2: Testing the Sensor Return (Ground) Circuit

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1/ 2

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If you've reached this point, then you've confirmed that the TPS is getting power (5 Volts DC) from the PCM.

The next test is to confirm that the PCM is feeding the TPS with ground.

This test follows pretty much the same procedure as TEST 1. Just a friendly reminder... the Ground Circuit is provided by the PCM, so do not short this circuit to Power (12 Volts) either intentionally or accidentally.

OK, let's start:

1. Put your multimeter in Volts DC mode.
2. With the BLACK multimeter lead, and an appropriate tool, probe the circuit labeled with the number 3 in the photo.
3. Connect the RED multimeter lead directly on the battery positive terminal.
4. Turn the Key to its ON position but do not start the engine.
5. Your multimeter should read battery voltage (11 to 12 Volts).

CASE 1: If the multimeter registered 11 to 12 Volts, then the PCM is feeding a good ground to the TP sensor. The next step is to verify that the TP sensor is creating a good Throttle Position Signal the PCM can use, go to: TEST 3: Testing the TP Signal.

CASE 2: If the multimeter DID NOT register 11 to 12 Volts, then there's a problem with the Ground Circuit, either because there's an open short in the circuit or the PCM is fried.

Altho' testing these two conditions are beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) on your Ford vehicle as being the cause of the problem and/or the TPS diagnostic trouble code (DTC) lighting up the check engine light (CEL).

TPS TEST 3: Testing the TP Signal

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OK, so far all of your tests have confirmed that the TP sensor is receiving juice (5 V) and ground, therefore it should be producing a good throttle position signal if all is good and this test will help you to find out.

You'll need someone to help you in this part to lightly tap on the throttle position sensor's body with a screw driver (or other appropriate tool) as you observe your multimeter and actuate the throttle.

OK, let's start testing:

1. Part 1
   1. Put your multimeter in Volts DC mode.
   2. With the RED multimeter lead, and an appropriate tool, probe the circuit labeled with the number 2 in the photo.
   3. Connect the BLACK multimeter lead directly on the battery negative terminal.
   4. Turn the Key to its ON position but do not start the engine.
   5. Your multimeter should read about .9 to 1 Volt (the reading on your vehicle will vary just a little, about ± 1 volt).
2. Part 2
   6. Now that everything is set up...
   7. Rotate the throttle plate by hand as you observe the multimeter.
   8. The multimeter's initial reading should increase smoothly as you open the throttle plate to its Wide Open Position.
   9. Now, slowly release the throttle plate to its fully closed position, all the while observing the multimeter's reading.
   10. The multimeter's voltage reading should decrease in a smooth and linear fashion.
3. Part 3
   1. OK, now have your assistant tap on the throttle position sensorlightly with a hard object, such as the butt of a screw-driver's handle.
   2. Have your assistant tap on it as you progressively open the throttle to its open-wide position and as you slowly release it back to its closed position.
   3. All the while you've got your eyes glued on the multimeter to see if the tapping affects the voltage readings.
   4. Repeat this (tapping the TPS) several times to make sure of your results.

Interpreting the Results

If the throttle position sensor (TPS) is good, the DC voltage on the multimeter should increase smoothly until it reaches it maximum voltage, which is about 4.5 Volts DC. As you slowly release the throttle plate back to its closed position, the multimeter again should display a gradual decrease in voltage till it reaches the initial base voltage you recorded in the beginning of the test.

If the TPS is BAD, then there will be sudden gaps/loss of voltage as you increase or decrease the throttle plate's to its fully open or fully closed position, especially when you tap on the sensor. Or, there will be no voltage reading at all. OK then, here are the two possible outcomes:

CASE 1: If the multimeter registered a smooth increase or decrease in voltage, then the TP sensor is working OK and is not the cause of the TPS fault code issue. Go to TEST 4 for a few more suggestions as to what could be causing the TPS diagnostic trouble code (DTC).

CASE 2: If the multimeter DID NOT register a smooth increase or decrease in voltage, then the throttle position sensor (TPS) is BAD. Replacing the throttle position sensor will solve the TPS diagnostic trouble code (DTC) lighting up your CHECK ENGINE LIGHT (CEL) on your Ford (or Lincoln or Mercury) car, Pick Up, or SUV.

TPS TEST 4: TPS Code Won't Go Away

So you've tested the TPS per the instructions in this article and according to the test results, the TPS is good... yet the CHECK ENGINE LIGHT is still on. Well, here are a couple of suggestions that might inspire your next diagnostic move:

1. The throttle plate's idle-stop screw's factory adjustment has been altered so that the engine could be idled up and mask a miss/misfire and/or rough idle. This increases the TP sensor's signal to the PCM. The PCM doesn't like it and light ups the CHECK ENGINE LIGHT (CEL).
2. The throttle cable is binding and causing the throttle plate to not fully close.
   1. This can be verified by simply having someone inside the vehicle pushing the accelerator cable to the floor and releasing it, with the engine OFF, while you visually check that the throttle plate and cable are not getting stuck somewhere in their travel.
3. The TPS is failing intermittently. Which means that it works fine most of the time, but every now and then... it doesn't:
   1. I have found that the best way to test these intermittents is to road-test the vehicle with the multimeter hooked up to the TP Signal Wire with a long wire so that I can comfortably observe the Signal going up and down as I or someone else drives.
4. The TP sensor's connector is BAD, usually the locking tab is broken and the connector has worked itself loose, causing an intermittent false connection.

How to Replace a Throttle Position Sensor

Throttle Position Sensor Replacement

Safety Tip:
Always wear safety glasses when working on your vehicle. Wear other personal protective equipment (PPE) when necessary, for example latex gloves or closed toe shoes.

1

Locate the OBD data link connector (DLC). Refer to your owner's manual for the specific location.

2

Turn your key to the ON position. Do not start the engine.

3

Plug your scan tool into the OBD data link connector. Turn on the scan tool and select the appropriate steps to read the diagnostic trouble code (DTC).
Photo may not be specific to your vehicle

4

Locate the throttle position sensor.
Photo may not be specific to your vehicle

5

Disconnect the electrical connector from the throttle position sensor.
Photo may not be specific to your vehicle

6

Test the resistance of the throttle position sensor (TPS) with a digital multi-meter. If the resistance is out of specifications, the TPS must be replaced.

7

Remove the throttle position sensor. Clean the sensor connector as needed using electrical contact cleaner or spray.
Photo may not be specific to your vehicle

8

Install the new throttle position sensor. Tighten the mounting screws and attach the electrical connector.

9

Erase the diagnostic trouble code (DTC) with the scan tool using the delete or erase command. Road test your vehicle to see if the check engine light returns.
Photo may not be specific to your vehicle

Troubleshoot All types Of Car Problem With proper Solutions

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Know Exactly How Each And Every Part In Your Car Works

http://carrepairworld.blogspot.com/2015/04/how-does-it-work.html

 

Troubleshoot Car OBD Codes.Know Exactly What Each Code Means?

http://carrepairworld.blogspot.com/2015/04/vehicle-obd-ii-codes.html