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.
When the vehicle speed sensor fails or the wiring harness prevents signal transmission, the speedometer is the first thing that will stop functioning properly. This can be an intermittent issue where the speedometer only works occasionally, the speedometer may cease all function, or the speedometer may read erratically or incorrectly. Also, the traction control and anti lock brake warning lights specific to each vehicle may be illuminated, depending on the design of those systems. You may notice the vehicle hesitate to accelerate, cruise control will not function properly, and the vehicle may not shift properly through all of the gears.
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.
The cruise control switch can cause complete failure of the cruise control feature, but in a lucky scenario only partial functionality will be lost. This means that the cruise control may come on, but that it will not increase in speed automatically, or the cancel button does not work leading the driver to cancel cruise control with the foot brake. In some vehicles, the cruise control light may illuminate, or a warning message may be displayed due to lack of functionality.
To effectively diagnose the non-functioning cruise control in a 1991 BMW M3, begin with a systematic approach that prioritizes simpler checks before delving into more complex diagnostics. Start by identifying any obvious issues, such as malfunctioning high beam switches or flashers, which could indicate broader electrical problems. Next, utilize a BMW scanner to read fault codes, as this will provide insight into specific system failures. Following this, inspect key components including the cruise control switch, brake switches, and wiring connections to ensure they are operational. Pay particular attention to the clock spring, as it is essential for maintaining the connection between the steering wheel controls and the cruise control system. Additionally, verify the functionality of the rear brake light switch, since its failure can directly impact cruise control operation. If your vehicle is equipped with Adaptive Cruise Control (ACC), be sure to troubleshoot this system as well, as any misadjustments or faults here could also affect overall functionality. By adhering to this diagnostic approach, you can efficiently pinpoint the issues affecting your cruise control and take the necessary steps to restore its operation.
When dealing with cruise control issues in a 1991 BMW M3, it's essential to understand the various common problems that could be at play. One frequent culprit is sensor malfunctions, which can disrupt the system's ability to maintain speed. Additionally, if the vehicle has undergone a manual transmission conversion, this may interfere with the cruise control's functionality, as the system may not be properly calibrated for the new setup. Coding errors are another significant factor; incorrect programming can lead to the cruise control appearing to function initially but failing to maintain speed, often accompanied by error messages. Lastly, electrical problems, which are not uncommon in older BMW models, can severely impact the cruise control system, preventing it from engaging or maintaining the desired speed. By systematically checking these areas, DIYers can effectively troubleshoot and resolve cruise control issues in their BMW M3.
While the cruise control system in your 1991 BMW M3 may not be critical for the vehicle's basic operation, neglecting its repair can lead to more significant issues down the line. A malfunctioning cruise control could signal problems with essential components like sensors or the speedometer, which, if left unchecked, might escalate into more serious electronic system failures. Additionally, a properly functioning cruise control enhances driving comfort, especially on long journeys, reducing fatigue and allowing for a more enjoyable experience. Therefore, while it may not be an immediate emergency, addressing the cruise control issue promptly is advisable to prevent potential complications and ensure the overall health and safety of your vehicle. Taking the time to diagnose and repair this system can save you from more extensive repairs in the future, making it a worthwhile DIY project.
See what others are asking about their BMW M3. Get answers from RepairPal's community of auto experts and enthusiasts.
Read about related problems experienced by other BMW M3 drivers like you.
