For 1990-2009 cars

### Important Preliminary Checks Before Starting

Perform the Diagnostic System Check - Engine Controls and verify all of the following before using the symptom tables:

• | The powertrain control module (PCM) and the malfunction indicator lamp (MIL) are operating correctly.

• | Check that there are no DTCs stored.

• | The scan tool data is within a normal operating range.

• | Verify the customer complaint and locate the correct symptom in the table of contents. Check the items indicated under that symptom.

Several of the symptom procedures call for a visual/physical check. DO NOT neglect to perform the visual/physical check. It is an important procedure that can correct a concern without further diagnosis, and save valuable time. The careful visual/physical check should include the following:

• | Verify all PCM ground connections are secure, clean, and in the proper locations.

• | Check all vacuum hoses for splits, kinks, and proper connections, as shown on the Vehicle Emission Control Information label. Check the vacuum hoses thoroughly for any type of leak or restriction.

• | Verify the mass air flow (MAF) sensor installation is correct.

• | Inspect the air inlet ducts for collapsed or restricted sections.

• | Check for air leaks at the throttle body mounting area, the MAF sensor, and the intake manifold sealing surfaces.

• | Inspect the ignition coil boots for cracking, hardening, and carbon tracking.

• | Inspect the wiring harness for proper connections and for damage.

For more symptom base diagnostics refer to the following tables:

• | Hard Start

• | Surges/Chuggles

• | Lack of Power, Sluggishness, or Sponginess

• | Detonation/Spark Knock

• | Hesitation, Sag, Stumble

• | Cuts Out, Misses

• | Poor Fuel Economy

• | Poor Fuel Fill Quality

• | Rough, Unstable, or Incorrect Idle and Stalling

• | Dieseling, Run-On

• | Backfire

• | Restricted Exhaust

• | Malfunction Indicator Lamp (MIL) Inoperative

• | Malfunction Indicator Lamp (MIL) Always On