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
Checking secondary ignition system
Checking engine vacuum
Checking the fuel pressure
Checking coolant sensor calibration
Checking throttle position sensor calibration
Checking MAP sensor calibration
Checking the minimum idle air flow
Checking idle air control motor operation
Checking engine mechanical systems
Checking EVAP emission system
Checking EGR system
Checking IAT sensor

Start and Stall
Checking secondary ignition system
Checking PCM power and gnd ckt
Checking the fuel pressure
Checking coolant sensor calibration
Checking throttle position sensor calibration
Checking MAP sensor calibration
Checking the minimum idle air flow
Checking idle air control motor operation

Hesitation/Sag/Stumble
Checking secondary ignition system
Checking PCM power and gnd ckt
Checking engine vacuum
Checking the fuel pressure
Checking coolant sensor calibration
Checking throttle position sensor calibration
Checking MAP sensor calibration
Checking the minimum idle air flow
Checking for oxygen sensor switching
Checking O2S heater
Checking idle air control motor operation
Checking engine mechanical systems
Checking EVAP emission system
Checking EGR system
Checking IAT sensor
Checking PNP switch

Surge
Checking secondary ignition system
Checking PCM power and gnd ckt
Checking the fuel pressure
Checking coolant sensor calibration
Checking throttle position sensor calibration
Checking MAP sensor calibration
Checking the minimum idle air flow
Checking for oxygen sensor switching
Checking idle air control motor operation
Checking EVAP emission system

Lack of Power/Sluggish
Checking secondary ignition system
Checking PCM power and gnd ckt
Checking the fuel pressure
Checking coolant sensor calibration
Checking throttle position sensor calibration
Checking MAP sensor calibration
Checking the minimum idle air flow
Checking for oxygen sensor switching
Checking idle air control motor operation
Checking EGR system

Spark Knock/Detonation
Checking secondary ignition system
Checking PCM power and gnd ckt
Checking the fuel pressure
Checking coolant sensor calibration
Checking throttle position sensor calibration
Checking MAP sensor calibration
Checking the minimum idle air flow
Checking for oxygen sensor switching
Checking idle air control motor operation
Checking EVAP emission system

Cuts Out/Misses
Checking secondary ignition system
Checking PCM power and gnd ckt
Checking the fuel pressure
Checking the minimum idle air flow
Checking for oxygen sensor switching
Checking idle air control motor operation
Checking EGR system

Backfire/Popback
Checking secondary ignition system
Checking PCM power and gnd ckt
Checking the fuel pressure
Checking MAP sensor calibration
Checking the minimum idle air flow
Checking for oxygen sensor switching
Checking EGR system

Runs Rough/Unstable/Erratic Idle
Checking secondary ignition system
Checking PCM power and gnd ckt
Checking engine vacuum
Checking the fuel pressure
Checking coolant sensor calibration
Checking throttle position sensor calibration
Checking MAP sensor calibration
Checking the minimum idle air flow
Checking for oxygen sensor switching
Checking O2S heater
Checking idle air control motor operation
Checking engine mechanical systems
Checking EVAP emission system
Checking EGR system
Checking IAT sensor
Checking PNP switch

Poor fuel Economy
Checking secondary ignition system
Checking PCM power and gnd ckt
Checking engine vacuum
Checking the fuel pressure
Checking coolant sensor calibration
Checking throttle position sensor calibration
Checking MAP sensor calibration
Checking the minimum idle air flow
Checking for oxygen sensor switching
Checking O2S heater
Checking idle air control motor operation
Checking engine mechanical systems
Checking EVAP emission system
Checking EGR system
Checking IAT SENSOR
Checking PNP switch