Nothing is more frustrating than firing up your Bronco only to discover that your engine's idle is off. There are a variety of isssues that could be causing this problem, and we'll explore some common areas to look at.
Basic Idle Relearn
This will serve as your primary solution when encountering any idle issues with the OBS Bronco. It typically addresses a majority of problems that may be contributing to erratic idle quality.
Please Note: These steps MUST be performed in sequence!!! - Get Engine To Operating Temperature
- Disconnect IAC (Idle Air Control) Solenoid. If engine stalls, turn the throttle stop screw in one full turn and restart. Repeat as necessary until the engine will idle with IAC unplugged.
- Set idle using throttle stop. Idle speed can vary depending upon mods made to the engine. Set to where you are comfortable with the idle speed.
- Set TPS (Throttle Position Sensor) anywhere from .96 to .98 volts. This is done by loosening the mounting screws and lightly rotating TPS. If you can’t obtain the desired range, you may need to make the mounting holes a little larger. This can be done by drilling them.
- TPS wire colors to be probed are generally BLACK and GREEN wires or the GRAY/RED and GRAY/WHITE, depending on your vehicle.
- Stop the engine. Disconnect negative terminal battery cable for 15-20 minutes. You may wish to tap the brakes or turn the headlights on and off a few times as this will help to ensure that you have purged any remaining electrical current from the vehicle.
- Reconnect IAC Solenoid
- Reconnect Battery Cable To The Negative Terminal
- Restart Engine
- Check For Proper Idle Function
Idle Air Adjuster Plate
The Idle Air Control Adjuster spacer service kit is designed to resolve certain idle issues that may arise following modifications like a cam installation. It is essential to confirm that the idle speed problem is not attributed to issues with the fuel system, IABP solenoid, throttle linkage, ignition system, PVC system, EGR system, cooling system, or vacuum leaks before proceeding with the installation of the idle air adjuster.
Ignition Timing Components
The ignition system of your Bronco is also an integral part to help control a good idle. If anything is worn or defective, these areas will need to be addressed. You will need to verify the actual timing as well on the vehicle. Common items will include the following list below:
- Cap/Rotor
- Distributor
- Ignition Wires
- Spark Plugs
- TFI Module
Vacuum Leaks
Vacuum leaks are another common issue due to age. These plastic and rubber lines and tend to rot or break over time. When the engine vacuum is off, idle quality can suffer and be very erratic. Common areas will include the following:
- PCV System
- Intake Manifold Gaskets
- Brake Booster & Lines
- Smog System & Lines
OBS Bronco Vacuum DiagramRecent Modifications Added To The Vehicle
Many Bronco enthusiasts face a common problem when they upgrade their vehicles with performance parts, such as a new air intake or camshaft. These modifications can lead to issues with how the engine idles. Everything we've talked about so far falls into this category. Things like missing gaskets, incorrect TPS voltage settings, problems with ignition, and issues with vacuum levels can all happen when you add new parts. Let's take the example of replacing an intake manifold. To do this, you need to deal with all the potential problems we've discussed. It's important to take your time, make sure the parts are in the right position, and follow the instructions carefully – doing so will help you a lot.
Charging System
Many people forget to check there charging system. If your car's charging system and battery are not working properly, it can also affect how smoothly your engine idles. One of the easiest ways to check your charging system is to
test your alternator.
OBS Bronco Cranks But Won't Start ChecklistEngine Compression
Idle problems in your Bronco can result from various issues, whether it's a gasket leaking or a cylinder not working at all. Imbalances like these in the engine can cause trouble with your idle. Local auto shops are usually equipped to help you figure out and fix these kinds of problems accurately.
These basic areas will provide an excellent starting point when attempting to identify and solve idle issues with your Bronco important to note that if you feel unsure about these procedures, it's advisable to seek assistance from your local automotive shop or a professional technician. Certain steps may involve the use of specialized tools that may not be readily available to everyone.
Source: Ford Performance & Alldata.com
