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1999 Ford Taurus P1507 and P1156: Idle Issues, Throttle Surge, and Solutions

Model: 1999 Ford Taurus Fault Code: P1151 Posted: 2009-12-31 15:42

Hello everyone, My mother's 1999 Ford Taurus is experiencing difficulty idling when cold-starting, and occasionally surges in throttle speed while driving or parked—especially after warming up. The OBD2 scan revealed codes P1507 and P1151. Based on my limited research, I suspect issues with the Idle Air Control (IAC) valve or vacuum lines. I performed a simple test by disconnecting the IAC while idling—the engine dropped to a very low RPM, which suggests the IAC may not be functioning properly under normal conditions. I inspected all visible vacuum hoses and found no leaks or hissing sounds. I also replaced the fuel filter as a preventive measure. Next, I plan to replace the PCV valve and clean the Mass Air Flow (MAF) sensor using Auto Zone cleaner. However, I'm seeking expert insight into what this specific combination of codes—P1507 and P1151—might indicate in a 1999 Ford Taurus. Any advice or troubleshooting steps would be greatly appreciated. Thanks in advance!

Related fault codes

P1151P1507

Comments (4)

Anonymous 2009-12-31 16:42

Before cleaning the MAF sensor, I'd recommend first thoroughly cleaning the throttle body and intake ports. Built-up carbon deposits can cause erratic idle and throttle response.

Anonymous 2010-01-03 05:19

I replaced the PCV valve and hoses, but that didn't resolve the issue. Can carburetor cleaner be used on the throttle body? I've read that some internal linings—like Teflon coatings—can be damaged by chemical cleaners. Any guidance on safe cleaning methods would be helpful.

Anonymous 2010-01-03 21:02

Ford does not recommend using chemical cleaners on throttle bodies due to the risk of damaging the internal Teflon coating. While an IAC valve may appear functional during a disconnect test, it can still stick or fail silently—especially if the solenoid is faulty. Use a digital multimeter (DMM) to check the IAC solenoid resistance; it should read approximately 10 ohms. This won't detect a stuck valve, but it helps rule out electrical faults. The P1151 code points to either a fuel system issue or an oxygen sensor problem. If the engine is running rich, spark plugs will show sooty black deposits and exhaust may emit a strong gasoline odor—possibly even black smoke. A faulty fuel pressure regulator or a stuck lean O2 sensor could also be at play. To test the O2 sensor: apply a propane torch to the tip of the sensor while it's in the exhaust stream. The voltage should read around 0.5V with a blue flame, then drop back to near 0V within 1–2 seconds after the flame is removed. If this doesn't happen, replace the O2 sensor.

Anonymous 2010-01-07 06:59

Thanks for the detailed response. I warmed up the engine enough to achieve a rough idle and then tapped the IAC valve with a wrench—immediately after, the engine surged and stabilized at a smooth idle. This confirms that the IAC is likely sticking. There's no black smoke or strong fuel odor from the exhaust. I'm now planning to replace both the IAC valve and the O2 sensors and hope this resolves both P1507 and P1151 codes. Appreciate your help!