LOW IDLE (STALLS ON DECELERATION)
Check Idle Air Control (IAC) wiring harness connector. Check for vacuum leaks. Ensure vacuum hoses are routed properly. Check air intake duct.
Check the following items:
On A/T models that stall or quit on deceleration, Torque Converter Clutch (TCC), TCC solenoid or TCC circuit may not be functioning properly. See appropriate OVERHAUL or ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS.
For low idle with A/C on, (Econoline 4.6L, 5.4L and 6.8L), check ACCS PID value. See PIN VOLTAGE/PID VALUE CHARTS - TRUCKS article. With A/C clutch engaged, ACCS PID value should indicate ON. If ACCS PID value indicates OFF, go to TEST KM, step 10) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article.
Check fuel delivery system. On Natural Gas models, go to TEST HB, step 1). On all other models, go to TEST HC, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article.
Check air intake system. Go to TEST HU, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article.
Check engine mechanical condition. Check compression, camshaft, valve train components, etc. And repair as necessary. See appropriate article in ENGINES. If engine mechanical condition is okay, check fuel filler cap for damage or improper installation. Repair as necessary. If fuel filler cap is okay, go to TEST Z, step 1) under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article and check for intermittent faults.
Saturday, November 15th, 2008 AT 8:30 AM