PO 171

Double check all suspect areas that can cause a vaccuum leak, especially the PCV valve, and it's plumbing. The intake manifold, and throttle body gaskets can also cause a small vaccuum leak.Make sure that the intake duct between the throttle body and the MAF sensor is tight, and leak free. You really need a scanner that shows data, and not just codes, to diagnose a lean condition. This way, fuel trims, which show how much extra fuel is being added, or taken away, from the fuel system to maintain the proper mixture., can be monitored during testing. A positive fuel trim, indicates a lean mixture that is being compensated for. Fuel trims max out at about 30%. If you see a high fuel trim, either short term, or long term, there is air getting in past the MAF sensor, and it doesn't take much. Even a very small leak will cause the fuel trim to go up. At around 10%, for a determined period of time, and throttle position, and engine load,the Check Engine light will come on, and a P0171 will set. You can spray carburetor cleaner around suspect areas, and if the fuel trim drops, then there's your leak. Some Fords have a fuel trim that goes high at idle, but comes down as soon as the throttle is opened. the PCM will disregard this type of reading, but will set the code if the trim does not come down. A faulty Oxygen Sensor may also be giving the PCM erronous readings, and thus causing a false P0171. Make sure the exhaust has no leaks ahead of the oxygen sensors, they will draw air into the exhaust stream, and cause false P0171 codes, and sometimes false misfire codes.

just retiurned from the dealer with same code they tell me my intake manifold gaskets are leaking thats why the engine lite is on o171 didnt tell me i should get it done like NOW but it would cost around 700.00 ps i have a 97 ranger