Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSJAGUAR1991XJ-6 L6-4.0LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTEMISSION CONTROL SYSTEMSADJUSTMENTSBASE IDLE SPEED
1991 Jaguar XJ-6 L6-4.0L
Base Idle Speed
1991 Jaguar XJ-6 L6-4.0LSECTION Base Idle Speed
NOTE: Base idle speed should be set using Jaguar Diagnostic System (JDS) equipment. If JDS equipment is not available, use the manual method described here.
1. Warm engine to operating temperature above 185°F (85°C).
2. Switch ignition "OFF."
3. Switch ignition "ON," wait 5 seconds and unplug idle speed controller connector. Controller is on intake manifold, left side of engine between 2nd and 3rd injectors.
4. Switch ignition "OFF."
5. Wait 15 seconds and reconnect idle speed controller.
6. Repeat previous steps twice. The second time through, do not reconnect idle speed controller.
7. Start engine.
8. Base idle should be approximately 550 - 600 rpm. If not, adjust air bypass screw to bring idle speed within specification.
9. Switch ignition "OFF" and reconnect controller.
10. Start engine and ensure that idle speed is 650 - 800 rpm.
1. Warm engine to operating temperature above 185°F (85°C).
2. Switch ignition "OFF."
3. Switch ignition "ON," wait 5 seconds and unplug idle speed controller connector. Controller is on intake manifold, left side of engine between 2nd and 3rd injectors.
4. Switch ignition "OFF."
5. Wait 15 seconds and reconnect idle speed controller.
6. Repeat previous steps twice. The second time through, do not reconnect idle speed controller.
7. Start engine.
8. Base idle should be approximately 550 - 600 rpm. If not, adjust air bypass screw to bring idle speed within specification.
9. Switch ignition "OFF" and reconnect controller.
10. Start engine and ensure that idle speed is 650 - 800 rpm.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.