Engine Controls - Tests W/o Codes: Other Jaguar XJS Series 3

DIFFICULT TO START

1. Check for starter motor rotating too slowly.
2. Ensure ignition system is okay.
3. Ensure fuel system is okay.
4. Check for bad engine ground.
5. Check for auxiliary air valve malfunction (XJS).
6. Check for idle speed control valve malfunction (XJ6).
7. Check coolant temperature sensor.

ENGINE BACKFIRES

1. Check for excessively lean air/fuel mixture.
2. Check for an air intake leak. (Idle speed will usually be faster if air leak is present.)
3. Check for leaking air into or out of exhaust system.
4. Check for air leakage past valve guides or valves.
5. Ensure ignition timing is correct.
6. Check for incorrect valve timing.
7. Check for valves sticking open.

NO POWER

1. Check for burned or sticking valves.
2. Check for incorrect valve clearance.
3. Ensure fuel system is okay.
4. Ensure engine compression is okay.
5. Ensure ignition system is okay.
6. Check for incorrect camshaft timing.
7. Check for incorrect octane fuel.

ROUGH OR UNSTABLE IDLE

1. Check for burned or sticking valves.
2. Check for incorrect valve clearance.
3. Ensure engine compression is okay.
4. Check for blown head gasket.
5. Ensure ignition system is okay.
6. Ensure fuel system is okay.
7. Check for an intake air leak. (Idle speed will usually be faster if air leak is present.)
8. Check for air leaking into or out of exhaust system.

Intermittent Simulation

To reproduce the conditions creating an intermittent fault, use the following methods

1. Lightly vibrate component.
2. Heat component.
3. Wiggle or bend wiring harness.
4. Spray component with water.
5. Remove/apply vacuum source.

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic codes. Use test results to identify a faulty component or circuit.