For 1990-2009 cars

### Important Preliminary Checks

#### Before Starting

Before using this section, perform the Diagnostic System Check - Vehicle and determined that the following items are OK:

• | The control module, malfunction indicator lamp (MIL), and check engine are operating correctly.

• | There are no DTCs stored.

• | The scan tool data is within normal operating range. Refer to Scan Tool Data List .

Verify the customer complaint, and locate the correct symptom in the table of contents. Inspect the items indicated under that symptom.

### Visual/Physical Check

Several of the symptom procedures call for a careful visual/physical check. The importance of this step cannot be stressed strongly enough. This step can lead to correcting a condition without further inspections and can save valuable time. This inspection should include:

• | Control module grounds for the following conditions:

- | A clean connection

- | A tight connection

- | Proper location

- | Refer to Power and Grounding Component Views .

• | Vacuum hoses for the following conditions:

- | Splits

- | Kinks

- | Proper connections as shown on the Vehicle Emission Control Information label--Refer to Emission Hose Routing Diagram .

- | Leaks

- | Restrictions

• | Air leaks at the following components:

- | Throttle body mounting

- | Intake manifold sealing surfaces

• | Wiring for the following conditions:

- | Proper locations

- | Pinches

- | Cuts

• | Use the following tables when diagnosing a symptom complaint:

- | 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