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The P0301 code on your Ford Ranger is letting you know that it has detected a misfire condition on the cylinder closest to the front of the engine. There are several reasons for this particular malfunction, including a fault on the secondary ignition system, a bad ignition coil or a bad oxygen sensor. However, even a computer malfunction can trigger a wrong code. There are a few common causes for the P0301 code.
Step 1
Unplug the spark plug wire from cylinder number 1 or the one closest to the front of the engine. See the Tip section for more information.
Step 2
Remove the spark plug using a ratchet, ratchet extension and spark plug socket. Check the plug for oil deposits or ashes that might indicate oil leaks into the cylinder or poor fuel quality. Also, check the plug gap with a wire feeler gauge and adjust as necessary. Replace the spark plug if necessary.
Step 3
Inspect the spark plug wire you disconnected. Check for damaged insulation like burns and cuts. Also, check the condition of the wire terminals. Use an ohmmeter to check the wire resistance by touching the wire terminals with the ohmmeter leads. On average, you should read about 15,000 ohms per foot of wire. Replace the wire if necessary.
Step 4
Check the terminal on the distributor cap leading to the spark plug wire you disconnected. Inspect the condition of the terminal and make sure there are no cracks or other similar damage. Replace the cap if necessary.
Step 5
Measure the ignition coil primary and secondary resistance using your ohmmeter. Resistance range specifications vary depending on your particular Ranger model. Consult your service manual and replace the ignition coil if necessary.
Step 6
Check the fuel injector feeding the intake valve on cylinder number 1. Turn on the engine and let it idle. Using a mechanic stethoscope, make sure the fuel injector valve is opening and closing. If you hear an irregular clicking sound or no click at all, the injector might be failing or inoperative. Take your car for further inspection if necessary.
Double check the condition of engine sensors on your Ford Ranger. If in doubt, you may get a free scan reading of your vehicle computer from a local auto parts store. A sensor might be pointing to another fault related to the cylinder malfunction, like an oxygen sensor.
Tip
- A service manual for your particular Ford Ranger model will help you locate and identify components. It also provides troubleshooting specifications for the different components. Buy one at your local auto parts stores or consult one at your local public library.
Items you will need
- Ratchet, ratchet extension and spark plug socket
- Wire feeler gauge
- Ohmmeter
- Mechanic stethoscope
