All Fuel Systems
See Figures 1 and 2
The oxygen (O 2 ) sensor is a device which produces an electrical voltage when exposed to the oxygen present in the exhaust gases. The sensor is mounted in the exhaust manifold or turbocharger outlet and is electrically heated internally for faster switching when the engine is running. When there is a large amount of oxygen present (lean mixture), the sensor produces a low voltage. When there is a lesser amount present (rich mixture) it produces a higher voltage. By monitoring the oxygen content and converting it to electrical voltage, the sensor acts as a rich-lean switch. The voltage is transmitted to the engine controller which changes the fuel injector's pulse width. The injector changes the mixture.
Chrysler Electronic Spark Control (ESC), Electronic Fuel Injection (EFI), and Multi-Point Fuel Injection (MFI) Systems
The EFI system is also known as the Single-Point Fuel Injection, or as Throttle-body Fuel Injection. The ESC system is used on 1981-86 2.2L carbureted engines.
- Start the engine and allow it to reach operating temperature. Turn the engine OFF .
- Connect the positive lead of a multimeter (set to measure voltage) to the O 2 sensor signal wire and the negative lead to the engine ground. Backprobe the O 2 sensor connector to attach the multimeter to the circuit.
- Start the engine and run at 2000 rpm for two minutes.
- Return the engine to idle and read the voltage displayed by the multimeter. The voltage reading should fluctuate between 100-900 millivolts, as the O 2 sensor detects varying levels of oxygen in the exhaust stream.
Under normal conditions the O2sensor should fluctuate high and low. If the O2sensor voltage does not fluctuate, the sensor may be defective or the air/fuel mixture could be extremely out of range.
Prior to condemning the O
sensor, check the sensor response to changes in the fuel mixture as follows:
- Force the system rich by closing the choke plate for carbureted engines, or by using propane or another approved method for EFI and MFI engines. If the O 2 sensor reads now reads above 550 millivolts, the sensor is operating properly and the problems is elsewhere in the system. If the sensor fails to respond, replace the sensor and retest.
- Force the system lean by removing a vacuum line. If this causes the oxygen sensor voltage to read below 350 millivolts the sensor is operating properly and the problem is elsewhere in the system. If the sensor fails to respond, replace the sensor and retest.
Before installing a new oxygen sensor, perform a visual inspection. Black sooty deposits on the O2sensor SAtip may indicate a rich air/fuel mixture. White gritty deposits could be an internal antifreeze leak. Brown deposits indicate oil consumption. All of these containments can damage a new sensor.Chrysler Mikuni Feedback Carburetor System
The Mikuni carburetor system is used only on 2.6L engines.
- Warm the engine until the coolant reaches normal operating temperature.
- Using an accurate digital voltmeter or multimeter, backprobe the oxygen sensor connector.
- Start the engine and observe the reading on the voltmeter.
- When the engine is raced (thereby enrichening the mixture), the meter should show approximately 1 volt. The voltage should change as the engine returns to idle speed.
- If the sensor fails to perform as specified, replace the sensor and recheck system operation.
Before installing a new oxygen sensor, perform a visual inspection. Black sooty deposits on the O2sensor tip may indicate a rich air/fuel mixture. White gritty deposits could be an internal antifreeze leak. Brown deposits indicate oil consumption. All of these containments can damage a new sensor.Eagle Throttle-Body Fuel Injection
The Eagle TBI system is utilized only on the 2.5L Premier engine
The oxygen sensor heating element can be tested by connecting an ohmmeter test leads to terminals A and B of the sensor connector. Resistance should be below 10 ohms. Replace the sensor if an infinite reading is obtained.
Before installing a new oxygen sensor, perform a visual inspection. Black sooty deposits on the O2sensor tip may indicate a rich air/fuel mixture. White gritty deposits could be an internal antifreeze leak. Brown deposits indicate oil consumption. All of these containments can damage a new sensor.
REMOVAL & INSTALLATION
To remove the oxygen sensor, a special removal tool is needed. There are two types of sensors: standard and heated. Heated sensors have a multi-prong electrical terminal with three wires, and standard sensors have only a single wire connector. For standard sensors, use tool C-4589 or an equivalent from the aftermarket; for heated sensors, use C-4907 or equivalent. It is necessary to be able to adapt this tool to a torque wrench. Also needed is a thread tap to clean the sensor mounting threads.
- Make sure the engine has been turned off for several hours so all parts will have cooled sufficiently for safe handling.
- Disconnect the negative battery cable.
- Pulling on the plug and not the wiring, disconnect the oxygen sensor electrical lead.
- Install the special tool and unscrew the sensor from the exhaust manifold.
- Oil the threads in the exhaust manifold or turbocharger outlet, then turn the tap into the sensor threads to chase any corrosion or dirt out.
- If installing a new sensor, make sure to get the proper replacement parts. Sensors used with turbocharged vehicles have a terminal boot not used on other sensors. As previously mentioned, 1988 and later models use a heated sensor with a multi-prong plug.
- If the sensor is to be reinstalled, coat the threads with an anti-seizing compound (new O 2 sensors come already coated with an anti-seizing compound).
- Install the sensor and tighten it to 20 ft. lbs. (27 Nm).
- Reattach the electrical connector securely.
- Connect the negative battery cable.