LEMON Manuals: Even more car manuals for everyone
Home >> Isuzu >> 1999 >> Trooper Part Time >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Trouble Code Identification >> DTC P1171: Fuel System Lean During Acceleration >> Diagnostic Aids

Diagnostic Aids

A restricted fuel system may provide adequate fuel supply at idle, but not during acceleration. Water or alcohol in fuel may cause low HO2S voltage during acceleration. Check for defective or plugged fuel injectors. Check for low fuel.

  1. Perform On-Board Diagnostic (OBD) System Check. See BASIC DIAGNOSTIC PROCEDURES article. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. If any other component-related DTCs are set, diagnose them first. If no other DTC is present, go to next step.
  3. Check fuel level. Add fuel if tank is almost empty. If fuel was added, go to next step. If no additional fuel was required, go to step  5.
  4. Start vehicle and bring engine to normal operating temperature. Raise engine speed to 1200 RPM. Using scan tool, observe HO2S No. 1 voltage. If scan tool reading toggles between .1-.9 volt and voltage increases to high end of specification when throttle is opened half way for a few seconds, see INJECTOR BALANCE TEST in SYSTEM & COMPONENT TESTING article. If voltage is not as specified, go to next step.
  5. Turn ignition off. Relieve fuel pressure and install fuel pressure gauge. Start engine, bring to normal operating temperature and allow it to idle. Disconnect vacuum line to fuel pressure regulator and read pressure gauge. If pressure is 41-47 psi (2.8-3.3 kg/cm2 ), see OBD II SYSTEM CHECK in BASIC DIAGNOSTICS PROCEDURE article. If pressure reading is not as specified, go to next step.
  6. Check for restricted fuel lines or filter. If problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
  7. Turn ignition off. Remove fuel pump relay. Connect fused jumper wire between battery terminal (White/Black wire on 3.2L, or White wire on 3.5L) and fuel pump fuse terminal (Black/Red wire on 3.2L, or Black/Yellow wire on 3.5L). With fuel pressure gauge still connected, pinch off fuel return line. Do not allow fuel pressure to exceed 60 psi (4.2 kg/cm2 ). Manipulate fuel line to raise pressure to more than 47 psi (3.3 kg/cm2 ). If pressure increases to more than 47 psi (3.3 kg/cm2 ), check for an intermittent problem. See DIAGNOSTIC AIDS . If pressure does not increase to 47 psi (3.3 kg/cm2 ), go to next step.
  8. Check for faulty fuel pump, restricted fuel pump strainer, incorrect fuel pump, incorrect fuel grade or hot fuel. If any problem is found, repair as necessary. Retest system.
scientia non olet · About LEMON Manuals