For 1990-2009 cars

#### Hesitation, Sag, Stumble

Checks | Action
--- | ---
Definition: Momentary lack of response as the accelerator is pushed down. Can occur at any vehicle speed. Usually more pronounced when first trying to make the vehicle move, as from a stop sign. May cause the engine to stall if severe enough.
Preliminary |

• | Refer to Powertrain On Board Diagnostic (OBD) System Check .

• | Refer to Symptoms .

• | Search for service bulletins.

Sensor/System |

• | Check the oxygen sensor (O2S 1). The O2S 1 and HO2S 2 should respond quickly to different throttle positions. If not, check the O2S 1 for silicon or other contaminants from fuel or the use of improper RTV sealant. The sensor may have a white powdery coating. Silicon contamination causes a high but false O2S 1 signal voltage (rich exhaust indication). The PCM will reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Refer to oxygen sensor in Information Sensors/Switches Description .

• | Check the EGR valve for a stuck open pintle.

• | Check for proper operation of the MAP Sensor.

• | Check for proper operation of the TP sensor.

• | Check for proper operation of the ECT sensor.

Fuel System |

• | Check the fuel pressure. Refer to Fuel System Diagnosis .

• | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• | Check the injectors. Refer to Fuel Injector Balance Test .

• | Check items which can cause an engine to run rich (long term fuel trim is significantly in the negative range). Refer to DTC P0172 Fuel Trim System Rich .

• | Check items that can cause an engine to run lean (long term fuel trim is significantly in the positive range). Refer to DTC P0171 Fuel Trim System Lean .

• | Check for proper operation of the evaporative emission (EVAP) control system.

Ignition System |

• | Check for proper ignition voltage output with the spark plug jumper wires J 36012-A and spark tester J 26792 .

• | Check the spark plugs for the following conditions:

- | Wet or fuel fouled spark plugs

- | Cracks on the spark plugs

- | Wear

- | Improper spark plug gap

- | Burned electrodes or heavy deposits

• | If the spark plugs are fuel or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.

• | Check the ignition control module (ICM) for proper ground connection.

• | Check the ignition coils for cracks or carbon tracking.

Additional Checks |

• | Check for proper operation of the Automatic Transaxle.

• | Check the generator output voltage. Repair the generator if the output voltage is less than 11 volts or more than 16 volts.

• | If all procedures have been completed and no malfunctions have not been found, review and inspect the following items:

- | Visually and physically inspect all electrical connections within the suspected circuit and/or systems.

- | Check scan tool data.