- Visual/Physical Underhood Inspection

These diagnostic procedures are designed to find and repair engine performance problems. Follow the three steps shown below.

1. Do the on-car diagnostics work?To determine if on-car diagnostics are operating perform the diagnostic circuit check. This is always the first step when working on TBI. If the on-car diagnostics aren't working, the diagnostic circuit check will direct you to A-CHARTS DIAGNOSIS BY SYMPTOMS to repair the on-car diagnostics. If the car will not start, go to A-CHARTS DIAGNOSIS BY SYMPTOM, Chart A-3 Engine Cranks But Will Not Run.

2. If the on-car diagnostics are OK check to see if a trouble code is stored. If a trouble code is stored go to the trouble code number in TROUBLE CODE TEST CHARTS.

3. Is the fuel system controlling correctly?This is determined in the Diagnostic Circuit Check and doing the Field Service Mode Check. If the fuel system is not controlling correctly, go to A-CHARTS DIAGNOSIS BY SYMPTOM. If the Field Service Mode Check shows that the system is in closed loop and working properly, go to DIAGNOSIS BY SYMPTOM. DIAGNOSIS BY SYMPTOM lists several driveabilty symptoms and suggests checks of related components, wich may be found in C-CHARTS COMPONENT TESTING.

VISUAL CHECK

One of the most important checks that must be done before any diagnostic procedure is a careful visual check under the hood. This step often leads to repairing the vehicle without further steps. Inspect all vacuum hoses for pinches, cuts,or disconnects. Be sure to inspect hoses that may not easily be seen, hidden by the alternator, A/C compressor air cleaner etc. Inspect all electrical wires in the same way, for tight connections, burning, chaffing, or pinches.

THIS VISUAL CHECK IS VERY IMPORTANT AND MUST BE DONE THOROUGHLY.