Here is a list of things you should cehck through.
Check the following items:
Make sure that throttle linkage and/or TPS are not sticking or binding.
Make sure that initial ignition timing is properly set.
Check engine idle speed, both base idle and ECM idle.
Check Idle Air Control (IAC) system. Check for foreign material in IAC bore.
Check for proper operation of EGR system.
Check ISC/ILC operation.
Check P/N switch circuit. Also make sure that P/N switch is properly adjusted.
Check power steering pressure switch circuit.
Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter.
If rough idle only occurs when engine is hot, check PCV valve for proper operation, check evaporative emission control system, check for proper spark plug gap and check engine compression.
Monday, October 1st, 2012 AT 6:09 PM