Ford Expedition

There are at least a couple more possible cause for a rapid cyclic rate.

1. A high resistance ["partial"] short circuit in the circuit for the turn signals. Some examples being a wire pinched in a crevice in the sheet metal resulting in damage to the wire insulation allwing a very miniscule contact between the wire and the grounded sheet metal, or corrosion build up in one or all of the bulb sockets.

2. If a replacement bulb was the incorrect bulb, having a heavier filiment than the proper bulb, it would draw more current, possibly a lot, as the change of flash rate is dependent on current value. The heavier the filiment, the greater the current draw, the greater the current draw, the greater the flash rate.

3. Oh, there is another, but you didn't mention it, so it may not apply. The more bulbs which are on the circuit drawing current, the faster the rate. A very good example is when towing a trailer with lights plugged into your vehicle's light system. The additional "load" created by the larger number of bulb filiments burning, can cause the flash rate to be incredibly fast. For this problem, a "heavy duty" flasher module is made, and sold at most auto parts stores.

Starter Feed Circuit Tests Disable ignition system. Connect volt/ampere tester to battery terminals. Refer to operating instructions provided with tester being used. Verify that all lights and accessories are Off and transmission shift selector is in Park for automatic transmissions or Neutral for manual transmissions, then set parking brake.Rotate and hold ignition switch in Start position. Observe tester. · If voltage reads above 9.6 volts and amperage draw reads above 250 amps, proceed to starter feed circuit resistance test. · If voltage reads 12.4 volts or greater and amperage reads 0-10 amps, proceed to starter control circuit test. · If starter motor turns engine freely at times, but starting system is still suspected, engage starter several times while observing tester. A starting system that has a problem should fail while performing this procedure.

After starting system problem have been corrected, verify battery state of charge, disconnect all testing equipment and connect distributor.

Starter Feed Circuit Resistance Test The following test will require a voltmeter accurate to 1/10 of a volt. Disable ignition system. With all wiring harness and components connected properly, perform the following: · Connect positive lead of voltmeter to battery negative post, and negative lead to battery negative cable clamp. Rotate and hold ignition switch in Start position. Observe voltmeter. If voltage is not detected, correct poor contact between cable clamp and post. · Connect positive lead of voltmeter to battery positive post, and negative lead to battery cable positive clamp. Rotate and hold ignition switch in Start position. Observe voltmeter. If voltage is not detected, correct poor contact between cable clamp and post. · Connect positive lead of voltmeter to battery negative terminal, and negative led to engine block near battery cable attaching point.

Rotate and hold ignition switch in Start position. If voltage reads above .2 volt, correct poor contact at ground cable attaching point. If reading is still above .2 volt, replace ground cable. Remove starter heat shield (if equipped), then perform the following: · Connect positive voltmeter lead to starter motor housing and negative lead to battery negative terminal. Rotate and hold ignition switch in Start position. If voltage reads above .2 volt, correct poor starter to engine ground. · Connect positive voltmeter lead to positive battery terminal and negative lead to battery cable terminal on starter solenoid. Rotate and hold ignition switch in Start position. If voltage reads above .2 volt, correct poor contact at battery cable to solenoid connection. If reading is still above .2 volt, replace positive battery cable.

If resistance tests detect no feed circuit failures, replace starter motor.

Starter Solenoid Test Connect heavy jumper wire on starter relay between battery and solenoid terminals. If engine cranks, perform starter relay test. If engine does not crank or solenoid chatters, check wiring and connectors from relay to starter for loose or corroded connections. Repeat test and, if engine still does not crank properly, repair or replace starter as necessary.

Starter Relay Test Place transmission in Park. Apply parking brake. Check for battery voltage between starter relay battery terminal and ground. Connect jumper wire on starter relay between battery and ignition terminals. If engine does not crank, connect a second jumper wire to starter relay between ground terminal and good ground and repeat test. If engine cranks in step 3, transmission linkage is misadjusted or neutral safety switch is defective. If engine does not crank in step 3, starter relay is defective.

Follow this step by step and you will pinpoint the problem.

Additional Information provided courtesy of "/gi/dynamic/offsite.htm?site=http://www.alldata.com/"

Mass Airflow Sensor

Operation

The Mass Airflow (MAF) sensor directly measures the mass of air being drawn into the engine. The sensor output is used to calculate injector pulse width. The (MAF) sensor is what is referred to as a "hot-wire sensor". The sensor uses a thin platinum wire filament, wound on a ceramic bobbin and coated with glass, that is heated to 200*C (417*F) above the ambient air temperature and subjected to the intake airflow stream. A "cold-wire" is used inside the (MAF) sensor to determine the ambient air temperature.

Battery voltage from the EEC power relay, and a reference signal and a ground signal from the PCM are supplies to the (MAF) sensor. The sensor returns a signal proportionate to the current flow required to keep the "hot-wire" at the required temperature. The increased airflow across the "hot-wire" acts as a cooling fan, lowering the resistance and requiring more current to maintain the temperature of the wire. The increased current is measured by the voltage in the circuit, as current increases, voltage increases. As the airflow increases the signal return voltage of a normally operating (MAF) sensor will increase.

Testing

1. Using a multimeter, check for voltage by back probing the (MAF) sensor connector.

2. With the key ON, and the engine OFF, verify that there is at least 10.5 volts between the VPWR and GND terminals of the (MAF) sensor connector. If voltage is not within specification, check power and ground circuits and repair as necessary.

3. With the key ON, and the engine ON, verify that there is at least 4.5 volts between the SIG and GND terminals of the (MAF) sensor connector. If voltage is not within specification, check power and ground circuits and repair as necessary.

4. With the key ON, and the engine ON, check voltage between GND and SIG RTN terminals. Voltage should be approximately 0.34-1.96 volts. If voltage is not within specification, the sensor may be faulty.

Removal & Installation (4.6L & 5.4L)

1. Disconnect the negative battery cable.

2. Release the air cleaner clamp and separate the air cleaner halves.

3. Remove the grommet from the air cleaner housing and slide the grommet down the hardness.

4. Remove the (MAF) sensor plate and (MAF) sensor from the air cleaner.

5. Detach the (MAF) sensor from the harness.

6. Remove the retaining nuts and remove the (MAF) sensor.

7. Installation is the reverse of removal.

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A P0300 OBD code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.

• the engine may be harder to start
• the engine may stumble / stumble, and/or hesitate
• other symptoms may also be present

• Faulty spark plugs or wires
• Faulty coil (pack)
• Faulty oxygen sensor(s)
• Faulty fuel injector(s)
• Burned exhaust valve
• Faulty catalytic converter(s)
• Stuck/blocked EGR valve / passages
• Faulty camshaft position sensor
• Defective computer

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.