1990 Jaguar XJS Cruise Control Isn't Working

Diagnosing Common Issues with the Cruise Control System in Your 1990 Jaguar XJS and How to Fix Them

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Reviewed by
Aisha
Written by RepairPal Car Genius
Updated January 14, 2025
0%
30% chance it's the
Sensor
0%
25% chance it's the
Control Module
0%
25% chance it's the
Throttle
0%
20% chance it's
Something else
The most common reasons a 1990 Jaguar XJS cruise control isn't working are failed control module, sensor or switch issues, or throttle actuation problems.
  • Sensor: A faulty sensor can lead to incorrect readings, causing issues with engine performance or triggering warning lights on the dashboard.
  • Control Module: A faulty control module can result in erratic vehicle behavior or failure of various electronic systems due to improper signal processing.
  • Throttle: A faulty throttle body or a defective accelerator pedal position sensor may be causing inconsistent acceleration and poor engine response.
Proper diagnosis will determine the exact cause of your symptom, saving you money on unnecessary repairs. The diagnostic experts at RepairPal Certified shops have the right tools and experience to solve any symptom.

How much does it cost to fix a 1990 Jaguar XJS cruise control isn't working?

Common Repairs

The total repair cost will vary based on the condition of your vehicle and the number of repairs needed to fix your symptom. Proper diagnosis will save you money by finding the exact repairs needed to fix your car right the first time.

When the throttle position sensor fails, the engine's computer tends to overcompensate with fuel, leading black exhaust coming from the tailpipe. There is a strong possibility of engine misfires, and the check engine light will come on.

Throttle position sensors can also develop "dead spots," or certain places along the throttle curve where it doesn't get a reading. When this happens, the above symptoms can occur but then stop when you further press or let off the gas pedal.

In the event that a wheel speed sensor fails, the ABS, traction control system (TCS) and manufacturer specific stability control system lights will illuminate, informing the driver that the systems are disabled. The vehicle will be more prone to tire slip, and normal driving patterns may need to be adjusted to correct for the loss of computer control. On older vehicle's, the speedometer can be affected, causing illumination of the check engine light as well.

What are the initial steps to diagnose the non-functioning cruise control in a 1990 Jaguar XJS?

To effectively diagnose the non-functioning cruise control in your 1990 Jaguar XJS, start by checking the cruise control switch to confirm it is set to the ON position and inspect it for any visible damage. Next, turn your attention to the vacuum system; examine the rubber bellows for any signs of wear or leaks, as these components are essential for proper operation. Following this, verify all electrical connections associated with the cruise control system, ensuring they are secure and free from corrosion. If these initial checks do not resolve the issue, proceed to test the cruise control module to confirm its functionality. Additionally, inspect for any vacuum leaks throughout the vehicle, as these can significantly impact the cruise control's performance. Lastly, assess the condition of the speed control actuator bushing, as a worn bushing may hinder the system's operation. By following this structured diagnostic approach, you can systematically identify the root cause of the cruise control malfunction and take the necessary steps to restore its functionality.

How urgent is it to repair the non-functioning cruise control in a 1990 Jaguar XJS?

Repairing the non-functioning cruise control in your 1990 Jaguar XJS is not just a matter of convenience; it is a critical safety concern that should be addressed promptly. A malfunctioning cruise control system can lead to unexpected acceleration or failure to disengage, creating hazardous driving conditions for you and others on the road. Additionally, the ability to maintain a constant speed during long drives significantly reduces fatigue, making your journeys more comfortable. Ignoring these symptoms can result in more severe mechanical issues down the line, potentially leading to costly repairs or even accidents. Therefore, it is advisable to refrain from using the cruise control until the problem is resolved and to consult a trusted mechanic who can diagnose and repair the system effectively. Prioritizing this repair not only enhances your driving experience but also ensures your safety and that of others on the road.

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