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2002 Ford Taurus P0316 and P0302 Diagnostic: Causes and Fixes for Misfire at 77,000 Miles

Model: 2002 Taurus Fault Code: P0302 Posted: 2006-08-14 20:13

I understand what the OBD-II codes P0316 and P0302 mean, but I'm unsure of how to properly diagnose and fix the issue. My 2002 Ford Taurus with a standard EFI engine has 77,000 miles on it. I replaced the spark plugs about 5,000 miles ago (using Bosch Platinum plugs), though I did not replace the plug wires. The fuel injectors were cleaned in December at approximately 68,000 miles. I recently added a full tank of fuel injector cleaner. My current plan is to replace spark plug #2 again tomorrow, then proceed with replacing all plug wires and finally the coil pack. Is this a logical troubleshooting sequence, or am I missing any key steps? The vehicle has been running rough for about a week—most noticeably during low-speed acceleration, though it occasionally sputters at higher speeds as well. After replacing spark plug #2, the drive quality improved significantly. I will check the codes again after my wife returns from work tomorrow to confirm if the issue persists or resolves. I'm wondering whether the Bosch plugs could be contributing to the misfire, especially given reports of issues with certain brands in Ford vehicles. Any insight on proper spark plug selection for this model would be appreciated.

Related fault codes
P0302P0316
Comments (5)
Anonymous 2006-08-14 21:32

Try swapping injector #2 with a known good one and then clear the codes before driving to see if the misfire shifts to another cylinder. Why were the plugs replaced in the first place? Consider switching spark plug wires as well—if the injector swap doesn't resolve it. Also, inspect the spark plug's condition when removed—does it show signs of wetness or gas burning? I've seen cases where Bosch plugs caused issues in older Ford models. Does the engine feel rough under normal driving conditions?

Anonymous 2006-08-14 22:12

I'm not familiar with injector locations or how to remove them. The plugs were replaced because they hadn't been serviced in a long time, and the engine started running roughly. After replacing them, the roughness disappeared. The current misfire appeared suddenly—within one week—and has persisted ever since. It's consistently rough now, though severity varies. During low-speed acceleration, it sputters badly at times, then runs fine again. At other times, the sputtering occurs during higher-speed acceleration as well. I just replaced spark plug #2 and did a test drive—it drove noticeably better. I'll check the codes again after my wife returns from work tomorrow. Could the Bosch plugs be the root cause of this issue?

Anonymous 2006-08-15 08:37

Remove the current Bosch spark plugs and replace them with factory-approved Ford plugs. If the misfire persists, then inspect or replace the ignition wires and test injector resistance. Does the spark plug smell like fuel when removed? Is it wet or dry?

Anonymous 2006-08-15 18:42

After replacing spark plug #2, the vehicle ran smoothly. I cleared the codes and retested—no misfire detected. As suggested, I've just purchased six Autolite Double Platinum plugs to replace the Bosch ones. I was told that Autolite and original Motorcraft plugs are made by the same manufacturer (Honeywell). Is this accurate? Any confirmation on whether Autolite is suitable for a 2002 Taurus with an EFI engine? Thanks in advance for your input!

Anonymous 2006-08-15 21:52

Honestly, I wouldn't recommend using Autolite plugs in any vehicle I personally drive. While they may be mass-produced by Honeywell, they don’t perform as reliably as OEM Ford Motorcraft plugs. If the misfire returns, I’d advise switching to genuine Ford Motorcraft spark plugs for better compatibility and long-term reliability.