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2001 Ford Taurus 3.0L V6: P0401, P1131, P1151, P0304 Diagnosis - MAF Cleaning or Larger Engine System Issue?

Model: 2001 ford taurus 3.0v6 Fault Code: P0304 Posted: 2006-12-19 22:22

I'm experiencing multiple diagnostic trouble codes on my 2001 Ford Taurus 3.0L V6: P0401 (Exhaust Duct Flow Malfunction), P1131 (O2 Sensor Bank 1 Sensor 1 Slow Response), P1151 (O2 Sensor Bank 1 Sensor 2 Slow Response), and P0304 (Misfire in Cylinder 4). I've seen similar combinations before, and many suggest cleaning the Mass Air Flow (MAF) sensor as a solution. However, I'm wondering if the presence of P0304—indicating misfire in cylinder 4—is directly related to an incorrect fuel-air mixture, or whether these codes collectively point to a more serious issue such as intake manifold leakage or engine internal problems. Could this combination be a sign of a larger system failure rather than just a sensor issue? Any insights would be greatly appreciated.

Related fault codes
P0304P0401P1131P1151
Comments (3)
Anonymous 2006-12-20 07:40

P0401 is relatively new—this could indicate a developing exhaust flow issue, possibly related to EGR or catalytic converter performance. It's worth investigating further.

Anonymous 2006-12-20 09:05

All these codes appeared simultaneously. The car had a rough idle for about a week, not severe but noticeable. It would surge when stopped at traffic lights and drop to just a few hundred RPMs—though it didn't stall. A couple days ago, after starting, it began sputtering and ran very roughly as if cylinder 4 wasn't firing. However, it remains running smoothly at highway speeds. The issue is most pronounced at low engine speeds. This behavior suggests either a fuel delivery problem or an intake leak affecting cylinder 4 specifically. Thanks, Gary

Anonymous 2006-12-20 16:37

Start by checking and replacing the EGR valve and vacuum modulator (if equipped). However, if your vehicle has a DPFE sensor, that should be your primary focus—faulty DPFE sensors are common in this model year and can trigger multiple related codes including P1131, P1151, and misfire events.