Ford F150 Pickup. Manual — part 1608

z

Check Idle Air Control (IAC) system. Go to TEST KE: IDLE AIR CONTROL VALVE , step 1) under
SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.

Additional Intermittent Testing

Go to TEST Z: INTERMITTENT , step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-
FUEL & GASOLINE article.

NO-START/NORMAL CRANK

After repairing a no-start condition on models with electric Secondary Air Injection (AIR) system, disconnect
AIR solid state relay. Start and run engine until surplus fuel is used, and then reconnect relay. Disconnecting
AIR solid state relay may set a Continuous Memory DTC. After repairs are completed, clear DTCs. See
CLEARING CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - CNG, FLEX-FUEL
& GASOLINE article.

Preliminary Checks

Check Inertia Fuel Shutoff (IFS) switch. Check fuel pressure and quality (octane, winter/summer grade fuel,
methanol, etc.). Check add-on alarm/anti-theft devices. Check wiring harness connectors. Check for
disconnected or restricted air intake duct. Check fuses and relays.

Miscellaneous Component Or System Checks

Check the following:

z

Check fuel and ignition systems. Go to TEST KB: FUEL PUMP DRIVER MODULE , step 85) (LS
and Thunderbird), or go to TEST A: NO-START , step 1) (all others) under SYSTEM TESTS in SELF-
DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.

z

Check exhaust system for restriction. Go to TEST HF: CATALYST EFFICIENCY MONITOR &
EXHAUST SYSTEMS , step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-
FUEL & GASOLINE article.

z

Check engine mechanical condition. Check compression, camshaft, valve train components, etc. See
appropriate article in ENGINES.

Engine Will Now Start & Run Normally At Part Throttle

If engine starts and runs only at part throttle, check Idle Air Control (IAC) system. Go to TEST KE: IDLE
AIR CONTROL VALVE , step 2) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL &
GASOLINE article.

Additional Intermittent Testing

CAUTION: Extended cranking, due to a no-start condition, can load exhaust system

with raw fuel, which can damage catalytic converter after engine is started.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Trouble Shooting - No Codes - CNG, Flex-Fuel & Gasoline

Go to TEST Z: INTERMITTENT , step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-
FUEL & GASOLINE article.

SLOW RETURN TO IDLE

Preliminary Checks

Check for vacuum leaks. Check throttle linkage operation. Check throttle body.

Miscellaneous Component Or System Checks

Check the following:

z

Check PCV system. For Aviator and Mustang 4.6L, go to TEST HG: PCV SYSTEM , step 1) under
SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article. For all others,
go to TEST HG: PCV SYSTEM , step 4) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG,
FLEX-FUEL & GASOLINE article.

z

Check air intake system. Go to TEST HU: AIR INTAKE SYSTEM , step 1) under SYSTEM TESTS in
SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.

z

Check Idle Air Control (IAC) system. Go to TEST KE: IDLE AIR CONTROL VALVE , step 1) under
SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.

FAST IDLE OR DIESELS/RUNS ON

Preliminary Checks

Check for vacuum leaks. Check for deposits on throttle plate. Check throttle linkage operation. Check for
binding/sticking cruise control linkage. Check for air intake duct leaks. Check for leaking intake manifold
gasket. Check Idle Air Control (IAC) or Exhaust Gas Recirculation (EGR) valves. Ensure vehicle is at normal
operating temperature.

Engine Idles Fast

Turn ignition switch to OFF, then back to ON position. Using scan tool, select TP V and TPREL PIDs from
PID/DATA MONITOR & RECORD menu. Observe TP V and TPREL PIDs while wiggling TP sensor circuits.
At vehicle start, TPREL PID value will begin at about 1.25 volts and count down to the lowest TP V value read
since engine start-up. If TP V value goes below normal range, then increases again, TPREL will set to the lower
voltage. If TP V is about .04 volt more than TPREL value at closed throttle, PCM will go into part throttle
mode. Check for loose or worn throttle plates. If no concern is found, go to TEST Z: INTERMITTENT , step
1) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article and check for
intermittent faults.

NOTE:

If engine runs normally after ignition switch is turned to OFF position, check for
damaged ignition switch or IGN RUN or VPWR circuit for short to power. See
WIRING DIAGRAMS .

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Trouble Shooting - No Codes - CNG, Flex-Fuel & Gasoline

Miscellaneous Component Or System Checks

z

Check air intake system. Go to TEST HU: AIR INTAKE SYSTEM , step 1) under SYSTEM TESTS in
SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.

z

Check Idle Air Control (IAC) system. Go to TEST KE: IDLE AIR CONTROL VALVE , step 1) under
SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.

Additional Intermittent Testing

Go to TEST Z: INTERMITTENT , step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-
FUEL & GASOLINE article.

LOW IDLE (STALLS ON DECELERATION)

Preliminary Checks

Check Idle Air Control (IAC) wiring harness connector. Check for vacuum leaks. Ensure vacuum hoses are
routed properly. Check air intake duct.

Stall Or Quit On Deceleration (A/T Models)

Check Torque Converter Clutch (TCC), TCC solenoid or TCC circuit may not be functioning properly. See
appropriate OVERHAUL or DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

Low Idle With A/C On (Econoline 4.6L, 5.4L & 6.8L)

Check ACCS PID. Connect scan tool to Data Link Connector (DLC). Start engine and allow to idle. Using scan
tool, access ACCS PID from PID/DATA MONITOR & RECORD menu. With A/C clutch engaged, ACCS PID
value should indicate ON. On models where PCM cannot control A/C clutch on and off, PCM uses ACCS
circuit to determine additional load on engine. If ACCS PID does not indicates ON, go to TEST KM: A/C
CLUTCH RELAY & A/C CIRCUITS , step 10) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG,
FLEX-FUEL & GASOLINE article.

Miscellaneous Component Or System Checks

Check the following:

z

Check fuel delivery system. Go to TEST HB: NATURAL GAS FUEL DELIVERY SYSTEM , step 1)
(Natural Gas models), or go to TEST HC: GASOLINE FUEL DELIVERY SYSTEM , step 1) (all
others) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.

z

Check air intake system. Go to TEST HU: AIR INTAKE SYSTEM TEST HU, step 1) under SYSTEM
TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.

z

Check fuel filler cap for damage or improper installation. Repair as necessary.

z

Check engine mechanical condition. Check compression, camshaft, valve train components, etc. and
repair as necessary. See appropriate article in ENGINES.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Trouble Shooting - No Codes - CNG, Flex-Fuel & Gasoline

BACKFIRES

Preliminary Checks

Check vacuum hose routing. Check spark plug wiring (if equipped) for incorrect firing order.

Miscellaneous Component Or System Checks

Check the following:

z

Check secondary ignition system. Go to TEST JB: SECONDARY IGNITION , step 1) under SYSTEM
TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.

z

Check fuel delivery system. Go to TEST HB: NATURAL GAS FUEL DELIVERY SYSTEM , step 1)
(Natural Gas models), or go to TEST HC: GASOLINE FUEL DELIVERY SYSTEM , step 1) (all
others) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.

z

Check engine mechanical condition. Check compression, camshaft, valve train components, etc. and
repair as necessary. See appropriate article in ENGINES.

z

Check exhaust system for restriction. Go to TEST HF: CATALYST EFFICIENCY MONITOR &
EXHAUST SYSTEMS , step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-
FUEL & GASOLINE article.

Additional Intermittent Testing

Go to TEST Z: INTERMITTENT , step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-
FUEL & GASOLINE article.

LACK/LOSS OF POWER

Preliminary Checks

Check vacuum hose routing. Check for restricted air filter. Check wiring harness connectors. Check throttle
linkage. Check for obstructed radiator. Check Automatic Transmission Fluid (ATF) level.

Symptom Checks Using Scan Tool PIDs

Check and compare the following PID values to PID specifications in appropriate PIN VOLTAGE/PID
VALUE CHARTS article.

NOTE:

Ensure symptom is reported under normal driving conditions without excessive
engine/vehicle load. PCM is equipped with an engine RPM/speed limit function.
If programmed speed is exceeded, fuel delivery will shut off and DTC P1270 will
be set in PCM memory. If vehicle is equipped with a Knock Sensor (KS), a lack
of power may result when vehicle is operated with a breakout box installed at
PCM. KS circuits are not shielded in the breakout box, and KS signal noise may
be noticed by PCM. If this happens, spark timing will be retarded and a lack of
power may result.

2003 Ford Pickup F150

2003 ENGINE PERFORMANCE Trouble Shooting - No Codes - CNG, Flex-Fuel & Gasoline