Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is only intended to diagnose the following:

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

1. Check Possible Cause Of Misfire
   
   If vehicle runs out of fuel, a DTC may be stored in PCM memory. If vehicle has recently run out of fuel, clear PCM memory and retest system. If vehicle has not recently run out of fuel, go to next step.
2. Check For DTCs
   
   Turn ignition off. Connect New Generation Star (NGS) tester to DLC. Retrieve DTCs and view freeze frame data. If any misfire DTCs exist, go to next step. See MISFIRE TROUBLE CODES  table. If any other DTCs exist, service lowest number DTCs first and repeat QUICK TEST . If no DTCs are present, proceed to TEST Z , for intermittent diagnostic procedure.
3. Check Ignition System
   
   Inspect ignition wires for cracking and arcing. Check resistance of wires. Ignition wire resistance should be 7000 ohms per foot. Inspect distributor cap and rotor for carbon tracking, cracks or other damage. Remove spark plugs and inspect for deposits and wear. Replace components as necessary and repeat QUICK TEST . If ignition components are okay, go to next step.
4. Check Injector Circuit Resistance
   
   Turn ignition off. Disconnect PCM and inspect connector for corroded or pushed out pins. Repair as necessary. Measure resistance between suspect injector and PCM connector KAPWR circuit. See CIRCUIT PIN IDENTIFICATION  table. If resistance is 10-14 ohms, go to next step. If resistance is not 10-14 ohms, repair circuit or replace injector as necessary.
5. Check For Rich Or Lean Condition
   
   Reconnect all electrical connections. Turn ignition off. Using NGS tester, access short term fuel trim PID. Start and warm engine to normal operating temperature. If short term fuel trim PID is about zero percent, go to next step. If short term fuel trim PID is a positive value, go to step  7. If short term fuel trim PID is a negative value, go to step  10.
6. Check Vacuum System
   
   Visually inspect all vacuum hoses for kinks or damage. Check for proper hose routing. Ensure all vacuum connections are clean and tight. Repair or replace as necessary. If vacuum system is okay, go to next step.
7. Check Fuel Delivery System
   
   Go to TEST HC  and perform fuel delivery system diagnostic procedure. Repair as necessary. If fuel delivery system is okay, go to next step.
8. Check Injectors For Leakage
   
   Turn ignition off. Relieve fuel pressure. Remove fuel rail assembly from intake manifold (leave hoses and injectors attached). Turn ignition on (DO NOT crank engine). If any injector leakage is observed, replace or clean leaky injector. Repeat QUICK TEST . If no injector leakage is observed, go to next step.
9. Check EVAP System
   
   Go to TEST HX  and perform EVAP system diagnostic procedures. Repair as necessary. If EVAP system is okay, go to next step.
10. Check Engine Mechanical Condition
    
    Some engine mechanical faults can cause a misfire DTC. Perform the following tests to evaluate basic engine integrity:
    • Perform compression test.
    • Perform dynamic valve train analysis.
    • Check PCV system.
    • Check for vacuum leaks.

    Repair any mechanical problem(s) as necessary. If engine is in good mechanical condition, fault is intermittent. Go to TEST Z  or see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - VILLAGER article.