Possible Cause & Correction

- Check the following items.

• Check ignition wires for short or faulty insulation.
• Check Distributor cap (if equipped) for moisture, dust or cracks. Spray spark plug wires with a fine mist of water to check for shorts.
• Connect Spark Tester ST-125 to spark plug and check for adequate spark.
• Check ignition system for faulty grounds.
• Check that EST wiring harness is not routed too close to wiring which may cause induced voltage signals.
• Check ignition coil connections.
• Remove spark plugs and check for correct heat range, wear, cracks, wetness, improper gap or heavy deposits.
• Check for poor or contaminated (water) fuel.
• Check for improper fuel pressure.
• Check float level on carbureted vehicles.
• Using INJECTOR BALANCE TEST located in the article SYSTEM/COMPONENT TESTS , check fuel injected vehicles for plugged injectors.
• Check for EGR valve sticking open.
• Check ECM for proper ground circuits.
• TPS for sticking or binding. TPS voltage should be less than 1.25 volts at idle.
• Check for proper crank angle sensor (DIS and IDI) or pick-up coil (HEI distributor) resistance.
• Check for restricted exhaust as described in BASIC TESTING article in this section.
• Check for bent push rods, broken valve springs or worn camshaft lobes.