Possible Cause & Correction

Check for missing cylinder by:

• Disconnecting IAC motor connector. Start engine. Remove one spark plug at a time.
• If there is an RPM drop on all cylinders, proceed to ROUGH, UNSTABLE, OR INCORRECT IDLE, STALLING trouble shooting.
• If there is no RPM drop on one or more cylinders, or excessive variation in drop, check for spark on suspected cylinders using ST-125 Spark Tester (J-26792).
• If there is no spark, remove spark plugs in suspected cylinders and check for cracks, wear, improper gap, burned electrodes, and heavy deposits.
• Check spark plug wires by connecting an ohmmeter to each end of wire. If ohmmeter reading is greater than 30,000 ohms, replace wire(s).
• Check ignition coil and secondary voltage using ST-125 Spark Tester (J-26792).
• Check for restricted fuel filter, contaminated fuel, or low fuel pressure. See CHART A-6, FUEL SYSTEM PRESSURE TEST chart in the TBI TESTS/CODES article in this section.
• Check valve timing. Perform compression test.
• Check distributor cap and rotor for moisture, dust, cracks, or burns.
• Remove rocker covers. Check for bent push rods, worn rocker arms, broken valve springs, or worn camshaft lobes.