Engine Performance

If a loss of performance is noticed, timing belt or chain may have skipped one or two teeth. Camshaft and crankshaft timing should be checked. Refer to Engine, Timing Belt or Chain Installation.

It is important that the vehicle is operating to its optimum performance level to maintain fuel economy and lowest vehicle emissions. If vehicle is not operating to these standards, refer to Engine Diagnosis under Testing and Inspection. The following procedures can assist in achieving the proper engine diagnosis.
1. Test cranking amperage draw. Refer to Starting and Charging.
2. Check intake manifold for vacuum leaks.
3. Perform cylinder compression pressure test. Refer to Engine Diagnosis found under Testing and Inspection.
4. Clean or replace spark plugs as necessary and adjust gap as specified in Ignition System. Tighten to specifications.
5. Test resistance of spark plug cables. Refer to Powertrain Management.
6. Test ignition coils primary and secondary resistance. Replace parts as necessary. Refer to Powertrain Management.
7. Check fuel pump pressure at idle and different RPM ranges. Refer to Powertrain Management.
8. The air filter elements should be replaced as specified in Maintenance.
9. Inspect crankcase ventilation system.
10. Road test vehicle as a final test.