Possible Cause & Correction

Check the following items:

• Check for leaking fuel injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
• Check for alcohol contaminated fuel, correct fuel pressure or a restricted fuel injector.
• Check for fuel in pressure regulator vacuum hose. Replace pressure regulator if fuel is present.
• Check injector harness locations. Ensure injectors are connected to correct injector/cylinder according to firing order.
• Check for faulty PCV valve.
• Check Idle Air Control (IAC) system. Check for vacuum leak or high idle. Check for foreign material in IAC bore of throttle body. Check for proper connection of IAC valve electrical connector.
• Check for short between battery voltage and ignition feed circuits. See WIRING DIAGRAMS article.