Handling No Trouble Code Problems

Symptom checks cannot be used properly unless the driveability problem characteristic actually happens while the vehicle is being tested.

Select the symptom that most accurately describes the vehicle's driveability problem and then perform the test routine that pertains to this symptom. Perform each routine test in sequence until the problem is found. For definitions, see Glossary Of Terms.

SYMPTOM AND DIAGNOSTIC TEST

Hard Start Secondary ignition system
Engine vacuum
The fuel pressure
Coolant sensor calibration
Throttle position sensor calibration
MAP sensor calibration
The minimum idle air flow
Idle air control motor operation
Engine mechanical systems
EVAP emission system
EGR system
IAT sensor

Start and Stall Secondary ignition system
PCM power and ground circuit
The fuel pressure
Coolant sensor calibration
Throttle position sensor calibration
MAP sensor calibration
The minimum idle air flow
Idle air control motor operation

Hesitation/Sag/Stumble Secondary ignition system
PCM power and ground circuit
Engine vacuum
The fuel pressure
Coolant sensor calibration
Throttle position sensor calibration
MAP sensor calibration
The minimum idle air flow
For oxygen sensor switching
O2S heater
Idle air control motor operation
Engine mechanical systems
EVAP emission system
EGR system
IAT sensor
PNP switch

Surge Secondary ignition system
PCM power and ground circuit
The fuel pressure
Coolant sensor calibration
Throttle position sensor calibration
MAP sensor calibration
The minimum idle air flow
For oxygen sensor switching
Idle air control motor operation
Evap emission system

Lack of Power/ Secondary ignition system
Sluggish PCM power and ground circuit
The fuel pressure
Coolant sensor calibration
Throttle position sensor calibration
MAP sensor calibration
The minimum idle air flow
For oxygen sensor switching
Idle air control motor operation
EGR system

Spark Knock/Detonation Secondary ignition system
PCM power and ground circuit
The fuel pressure
Coolant sensor calibration
Throttle position sensor calibration
MAP sensor calibration
The minimum idle air flow
For oxygen sensor switching
Idle air control motor operation
EVAP emission system

Cuts Out/Misses Secondary ignition system
PCM power and ground circuit
The fuel pressure
The minimum idle air flow
For oxygen sensor switching
Idle air control motor operation
EGR system

Backfire/Popback Secondary ignition system
PCM power and ground circuit
The fuel pressure
MAP sensor calibration
The minimum idle air flow
For oxygen sensor switching
EGR system

Runs Rough/ Secondary ignition system
Unstable/Erratic Idle PCM power and ground circuit
Engine vacuum
The fuel pressure
Coolant sensor calibration
Throttle position sensor calibration
MAP sensor calibration
The minimum idle air flow
For oxygen sensor switching
O2S heater
Idle Air Control motor operation
Engine mechanical systems
EVAP emission system
EGR system
IAT sensor
PNP switch

Poor Fuel Economy Secondary ignition system
PCM power and ground circuit
Engine vacuum
The fuel pressure
Coolant sensor calibration
Throttle position sensor calibration
MAP sensor calibration
The minimum idle air flow
For oxygen sensor switching
O2S heater
Idle air control motor operation
Engine mechanical systems
Evap emission system
EGR system
IAT sensor
PNP switch