Idle control of some sort. 00 Impreza 2.2 throwing this code. The idle will dip up and down. How to fix? Thanks
do a search you noob... P1507 means "Idle Air Control Underspeed Error". It can be most commonly caused by a vacuum leak, a damaged Idle Air Control (IAC) assembly or a stuck IAC valve that needs cleaning. Essentially, your engine isn't idling at high enough according to your computer's programming parameters. Many times this shows up in colder weather as you try and start your vehicle. It will usually die unless you put your foot on the gas pedal and raise the RPM's. I have also read where a clogged air filter might be the problem. Try cleaning your IAC valve first.
taken from nabisco Remove the IAC by taking the 2 screws out that hold it in place. Screws are a PITA to get out, I had to use a set of vise grips. Remove the coolant line connected to the IAC. Be very careful removing the IAC because there is an O-ring type gasket between the TB and the IAC, this gasket can be damaged very easily. Take the IAC out and spray inside it with a throttle body cleaner, yours is probably very dirty like mine was. Inside the IAC you will notice a circular shaft the runs the length of the sensor. Using a small straight screwdriver, rotate the shaft (one end is set up to act like a flapper) and spray again with TB cleaner to remove the buildup. It takes very little pressure with the screwdriver to open the flapper. Let the TB cleaner dry, reinstall, and reset your computer. Watch when reinstalling the IAC to be sure the gasket is sitting in the groove. Also make sure the no antifreeze went through the ports in the TB where the IAC mounts (this happened to be and I had a nice puddle of antifreeze laying against the throttle plate and I had to remove the intercooler to dry up the coolant). This process is what cured my car and I have not had any problems since. It is a very easy process, I just tried to tell you every detail I could think of. I believe that the grime inside the sensor was causing the flapper to stick and caused the car to go into limp mode. Hope this helps and hit me back with any more questions.
