Diagnostic Aids

WARNING: This page is about a different car, the 1995 Ford Windstar and 1995 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.

Perform this test when instructed during QUICK TEST or if directed by other test procedures. Only use this test to diagnose:

Ignition system.
Fuel pressure.
Fuel injectors.
Engine vacuum system.
Evaporative system.
Canister purge solenoid.
Internal engine wear.

Fig 1: CKP Sensor & Crankshaft Wheel ID (Ranger & Windstar)

MISFIRE TROUBLE CODES

Service DTC	Application
90	Pass
P0301	Cylinder No. 1 (Test Pin No. 75)
P0302	Cylinder No. 2 (Test Pin No. 101)
P0303	Cylinder No. 3 (Test Pin No. 74)
P0304	Cylinder No. 4 (Test Pin No. 100)
P0305	Cylinder No. 5 (Test Pin No. 73)
P0306	Cylinder No. 6 (Test Pin No. 99)
P0307	Cylinder No. 7 (Test Pin No. 72)
P0308	Cylinder No. 8 (Test Pin No. 98)
P0300	Multiple Cylinder Misfire Or Defective CKP Sensor

1) Check Possible Cause Of Misfire

If vehicle runs out of fuel, a trouble code may be stored in PCM memory. If vehicle has recently run out of fuel, clear PCM memory. If vehicle has not recently run out of fuel, go to next step.

2) Check For Continuous DTCs

If continuous codes are present, service as necessary. Disregard misfire codes at this time. If no other misfire codes are present, go to next step.

3) Check For Other DTCs

If any other DTCs are present, service as necessary. Disregard misfire codes at this time. If no other DTCs are present, check spark plugs and spark plug wires. If spark plugs and spark plug wires are okay, go to step 8).

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 8). No test procedures have been omitted.

8) Check Fuel Injector & Circuit Resistance

Turn ignition off. Disconnect PCM 104-pin connector. Inspect pins for damage and repair if necessary. Install EEC-V Breakout Box (014-00959), leaving PCM disconnected. Measure and record resistance between suspected fuel injector test pin and test pin No. 71 and 97 at breakout box. If resistance is 11-18 ohms, go to next step. If resistance is not 11-18 ohms, go to CIRCUIT TEST H, step 47).

9) Check Fuel Injector Drive Signal

With ignition off, connect PCM to breakout box. Connect a non-powered 12-volt test light between test pin No. 71 or 97 and suspect fuel injector test pin at breakout box. Crank or start engine. If test light glows dimly, system is operating correctly. Clean fuel injectors. Drive vehicle for 5 miles and repeat QUICK TEST. If test light does not glow dimly (no light/bright light), replace PCM and repeat QUICK TEST.

10) Check Fuel Pressure

Turn ignition off. Release fuel pressure. Install fuel pressure gauge. Start engine and allow to idle. Note fuel pressure gauge reading. Increase engine speed to 2500 RPM and maintain for one minute. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to CIRCUIT TEST HC, step 9).

11) Check System Ability To Hold Fuel Pressure

Start engine and allow to idle. Note fuel pressure gauge reading. Increase engine speed to 2500 RPM and maintain for one minute. Check for fuel leaking from around fuel injectors, fuel pressure regulator and fuel hoses. Repair if necessary. Turn ignition off. Turn ignition on and note fuel pressure gauge reading. If fuel pressure remains at specification for one minute, go to next step. If fuel pressure does not remain at specification for one minute, go to CIRCUIT TEST HC, step 9).

12) Check Fuel Injector Flow & Leakage

Turn ignition off. Use Rotunda Injector Tester (113-00001) to flow test fuel injectors. If flow rate for each fuel injector is okay, go to step 20). If flow rate for any fuel injector is not okay, replace defective fuel injector and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 20). No test procedures have been omitted.

20) Check Vacuum System

Inspect all vacuum hoses for kinks or damage. Ensure all vacuum connections are clean and tight. Repair or replace as necessary. If vacuum system is okay, go to next step.

NOTE: The misfire monitor can be affected by the evaporative emission system.

21) Check Evaporative Emission System

Inspect carbon canister. Replace carbon canister if it contains liquid fuel. If carbon canister is okay, go to next step.

22) Pressure Test Evaporative System

Remove vapor line from canister and install vacuum tee. Connect a pressure gauge to one side of tee and low pressure air pump to other side of tee. Apply 0.75 psi (5.2 kPa). If evaporative emission system holds pressure, reconnect vapor line and go to next step. If system does not hold pressure, isolate fault and repair as necessary.

23) Check Vacuum In Evaporative System

Inspect vacuum hoses between engine and carbon canister for restrictions or damage. Ensure all vacuum connections are clean and tight. Repair or replace as necessary. If system is okay, go to next step.

24) Check Canister Purge Solenoid (CANP)

Turn ignition off. Disconnect CANP solenoid wiring harness connector. Inspect connector for damaged pins and repair as necessary. Using jumper wire, apply 12 volts to VPWR (Red wire) terminal of CANP wiring harness connector. Connect CANP (Gray/Yellow wire) terminal to ground. Apply 16 in. Hg to manifold side of CANP solenoid. When 12 volts is applied, solenoid should open and pass air freely. Replace solenoid if it does not function correctly. If solenoid does function correctly, go to next step.

25) Check Engine Condition

Inspect engine for obvious faults. Ensure compression is even and within specification. Check PCV system for restrictions or leaks. Repair or replace as necessary. If no faults can be found, misfire trouble code is intermittent. Go to CIRCUIT TEST Z.