Visual Inspection

All troubleshooting must begin by "CHECKING THE BASICS". Certain basic faults can be discovered by following a well thought out "game plan". Following the steps listed is the best way to begin troubleshooting.

COMPLAINT VERIFICATION
Whenever possible the repairing technician should personally verify the complaint. Having experienced the malfunction, the technician is less likely to try to repair non-existent faults.

MALFUNCTION VERIFICATION
Today's sophisticated automotive systems are easily misunderstood, which can lead to repairs that attempt to force a particular system to perform in a way that it was never intended to operate. Therefore, the troubleshooting technician should compare the system operation to the nominal system operation as described in the section Description and Operation. Furthermore, the technician is also encouraged to compare the problem vehicle system operation with a known good vehicle.

PREVIOUS REPAIRS
The vehicle repair history can provide explanations to unusual complaints which seem to elude normal troubleshooting attempts. Incorrect components or unapproved repairs can have subtle influences on seemingly unrelated systems.

VISUAL INSPECTION
A thorough visual inspection of all related components should be performed so that an obvious problem is not overlooked.

Electrical Connections
Terminals in connectors must lock together. Look for connections that are not fully plugged into each other or terminals that are not fully plugged into the insulator. Also make sure the wiring between each connector, and where it goes into the convolute of the harness, is not pinched behind any screws, bolts, or is rubbing on metal, which would result in a short to ground.
In addition to all electronic component connections, the following electrical connections should also be checked for integrity:

Under Hood
^ Battery cables
^ Engine to firewall ground strap
^ Spark plug wires
^ Fuses and fusible links

Passenger Compartment
^ ECM/MPI Control Module
^ MPI control relay
^ Fuse Block

Underbody Connection
^ In-Tank fuel pump

Hose And Vacuum Line Connections
All hose and vacuum line connectors must be fully and firmly fitted at their connections. Also, they cannot be pinched anywhere along their routing. Look for hoses and vacuum lines that are not fully plugged in, or are pinched, melted, or cut. Also, make sure hoses are not egg-shaped at their connection points causing a leak.

Replacing Components
Before replacing any vehicle component, inspect connector or connectors for pin or cavity damage that may result in a poor connection or an open circuit.

CHECKING THE BASICS
The following items should ALWAYS be checked:
^ Engine Vacuum- Must be at least 13 inches in neutral
^ Engine Valve Timing- To specifications
^ Engine Compression- To specifications
^ Engine Exhaust System- Must be free of any restrictions
^ Engine PCV System- Must flow freely
^ Engine Drive Sprockets- Cam and crankshaft
^ Torque Converter Stall Speed- To specifications
^ Power Brake Booster- No internal vacuum leaks
^ Fuel Contamination- High alcohol or water content
^ Fuel Injectors- Rough idle may be caused by injector control wire not connected to correct injector
^ Technical Service Bulletins- Any that may apply to vehicle
^ Engine Secondary Ignition Check- Any abnormal scope pattern
Any one or more of these items can give a driveability related problem. They cannot be overlooked as possible causes.

FUEL DELIVERY AND FUEL RAIL PRESSURE
Fuel delivery must begin at once when cranking and the pressure in the fuel rails must be within specifications. Fuel pressure retention must be maintained between the fuel pump outlet and the pressure regulator after engine shutdown.

AIR/FUEL RATIO
Adaptive engine management systems efficiently compensate for conditions which may affect the combustion process. However, when troubleshooting idle quality or driveability complaints, it is still necessary to consider the following:
^ Injector spray pattern quality
^ Presence of unmetered air leaks
^ Evaporative purge system
^ Excessive engine oil dilution
^ Substandard fuel or unapproved additives
^ Carbon build-up

TESTING EQUIPMENT
High standard testing equipment is essential if accurate results are expected. The use of faulty equipment will result in erroneous test results. Use only suitable test leads, terminals and probe tips.