Surges/Chuggles

SURGES AND/OR CHUGGLES
Definition: Engine power variation, under steady throttle or cruise. Feels like the vehicle speeds up and slows down, with no change in the accelerator pedal.

IMPORTANT PRELIMINARY CHECKS
Before using this section you should have performed the "On-Board Diagnostic System Check" - Powertrain/On-Board Diagnostic System Check and determined that:
1. The control module and MIL (Service Engine Soon) are operating correctly.
2. There are no diagnostic trouble codes stored, or there is a diagnostic code but no MIL (Service Engine Soon).
^ Several of the following symptom procedures call for a careful visual/physical check. The importance of visual/physical checks cannot be over stressed. because they can lead to correcting a problem without further checks and can save valuable time.

VISUAL / PHYSICAL CHECK
This check should include:
^ Control module grounds for being clean, tight, and in their proper location.
^ Vacuum hoses for splits, kinks and proper connections, as shown on "Vehicle Emission Control Information" label Check thoroughly for any type of leak or restriction.
^ Air leaks at all mounting areas of the intake manifold sealing surfaces.
^ Ignition wires for cracking, hardness, proper routing, or carbon tracking.
^ Wiring for proper connections, pinches, and cuts.
^ The following symptom charts contain groups of possible causes for each symptom and cover several engines. These procedures are not necessarily meant to be done in consecutive order. If Tech 1 scan tool readings do not indicate the problems, then proceed in a logical order, easiest to check or most likely cause first. To determine if a particular system or component is used on a specific vehicle, refer to the "Electronic/Powertrain Control Module (ECM/PCM)" Wiring Diagrams for application. Electronic/Powertrain Control Module (ECM/PCM)

^ Be sure driver understands Torque Converter Clutch (TCC) and A/C compressor operation.
^ Use a scan tool to make sure reading of VSS matches vehicle speedometer except vehicles with electronic transmissions where some variation between VSS and speedometer is normal. Refer to "DTC 16 Diagnostic Aids". DTC 16

SENSORS
^ CHECK: Oxygen Sensor (025) for silicon contamination from fuel, or use of improper sealant (never use any sealant on waterproof connectors). The sensor may have a white, powdery coating and result in a high but false signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem.

FUEL SYSTEM
^ CHECK: To determine if the condition is caused by a rich or lean system, the vehicle should be driven at the speed of the complaint. Monitoring fuel trim will help identify a problem.
- Lean - Long term fuel trim greater than 150. Refer to "DTC 44 Diagnostic Aids. DTC 44
- Rich - Long term fuel trim less than 115. Refer to "DTC 45 Diagnostic Aids". DTC 45

^ CHECK: Fuel pressure while condition exists, refer to "CHART A-6". Related Tests, Information and Procedures

IGNITION SYSTEM
^ CHECK: For proper ignition voltage output voltage using spark tester J 26792 or equivalent (ST-125).
^ CHECK: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.
^ CHECK: Ignition timing. Ignition Timing

ADDITIONAL CHECKS
^ CHECK: Control module grounds for being clean, tight, and in their proper locations.
^ CHECK: Generator output voltage. Repair if less than 9 or more than 16 volts.
^ CHECK: Vacuum lines for kinks or leaks.
^ CHECK: For intermittent EGR. Testing and Inspection
^ CHECK: TCC operation. Description and Operation