1991 Ford Probe Has Rough Idle

Diagnosing Common Causes of Rough Idle in Your 1991 Ford Probe and How to Fix Them

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Reviewed by
Devin Cabugcal
Written by RepairPal Car Genius
Updated January 14, 2025
0%
21% chance it's the
Spark Plugs
0%
15% chance it's the
Ignition Coil
0%
64% chance it's
Something else
The most common reasons a 1991 Ford Probe has rough idle are a vacuum leak, an issue with the spark plugs, or a problem with the ignition coil.
  • Spark Plugs: Worn or fouled spark plugs can lead to misfires, poor fuel economy, and difficulty starting the engine.
  • Ignition Coil: A faulty ignition coil can cause misfires, rough idling, and difficulty starting the engine due to inadequate spark delivery to the spark plugs.
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 1991 Ford Probe has rough idle?

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.

Here are a few common symptoms of worn-out brake pads:

  1. Low brake pad warning light is on: Not all vehicles are equipped with this system, but if yours is, this dashboard indicator light will likely be the first signal it’s time to replace your brake pads.
  2. Brakes start to squeal regularly: This is often one of the first signs of worn brake pads and is caused by a metallic piece built into brake pads for this exact purpose. This part contacts the brake rotor to make a squealing or whining noise when the pads are low.
  3. Brakes make loud grinding noise: If not addressed early enough, your brake pads may get so worn that the metal backing plate of the pad grinds against the metal rotor.
  4. Brake pads look thin: You may be able to visually check your brake pad thickness to determine if they need replacement.

Customers with drum brake systems often specify they have lost braking power, or that the vehicle's brakes are making noise. This is because brake drums do not dissipate heat very well, so the heat from hard braking will cause stress fractures. These fractures make can make noise on the brake shoes as the drum revolves around the shoes. Lastly, the brake shoes may not be problematic, but may cause a grinding noise while stopping. This would indicate the shoes have no braking material left, and the brake shoes must be changed before the vehicle can be safely driven.

Learn more about brake shoe symptoms

Most often, a brake system inspection will just be a routine portion of manufacturer specified maintenance, and will be performed at mileage intervals. In those cases, there will likely be no symptoms. However, when a brake system makes a funny noise, causes vibration, is hard to use, will not slow the vehicle, prevents the vehicle from driving, makes the vehicle pull to one side, or leaks brake fluid, the vehicle will need a visit dedicated to the inspection of the brake system.

What are the steps to diagnose a rough idle in a 1991 Ford Probe?

To effectively diagnose a rough idle in your 1991 Ford Probe, start with a systematic approach that prioritizes simpler checks before delving into more complex issues. Begin by inspecting the air intake system for any obstructions or leaks, as changes in airflow can significantly impact engine performance. Next, examine the ignition system, ensuring that spark plugs and wires are in good condition, as irregular ignition can lead to a rough idle. Don't overlook the vacuum lines; any cracks or disconnections can cause air leaks that disrupt the engine's air-fuel mixture. Once these basic checks are complete, verify the operation of the Exhaust Gas Recirculation (EGR) system, ensuring it is inactive during idle, as an active EGR can contribute to a rough idle. By following this structured diagnostic approach, you can efficiently identify and resolve the underlying issues affecting your vehicle's performance.

What are the common causes of a rough idle in a 1991 Ford Probe?

When troubleshooting a rough idle in a 1991 Ford Probe, it's important to systematically evaluate several key components that may be contributing to the problem. Start by inspecting for vacuum leaks, as these can significantly disrupt the air-fuel mixture, leading to an unstable idle. Next, consider the condition of the fuel injectors; dirty or malfunctioning injectors can impede fuel delivery, worsening the idle issue. Additionally, check the spark plugs for wear or damage, as faulty plugs can cause misfiring, which directly affects engine performance. The Idle Air Control Valve (IAC) is another critical component; if it’s not functioning properly, it can lead to irregular idle speeds. Don’t overlook the oxygen sensor, as a faulty sensor can mismanage the air-fuel mixture, while a clogged air filter can restrict airflow to the engine, both of which can contribute to rough idling. By addressing these common issues, DIYers can effectively diagnose and remedy the rough idle in their Ford Probe, ensuring smoother engine performance.

How urgent is it to address the rough idle in a 1991 Ford Probe?

Addressing a rough idle in your 1991 Ford Probe is not just a matter of comfort; it is crucial for the vehicle's overall health and performance. A rough idle can indicate serious underlying issues such as clogged fuel injectors, a dirty air filter, or a malfunctioning oxygen sensor. If left unattended, these problems can escalate, leading to decreased fuel efficiency, engine misfires, and even significant damage to engine components. The urgency of resolving a rough idle cannot be overstated, as neglecting it may result in costly repairs down the line and compromise the reliability of your vehicle. Regular maintenance and prompt attention to symptoms like a rough idle are essential to ensure your Ford Probe runs smoothly and efficiently, ultimately prolonging its lifespan and enhancing your driving experience.

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Diagnose Rough Idle Issues in 1991 Ford Probe | RepairPal