Hyundai Repair: 2001 Accent- Strange noise and P0507 code, throttle position sensor, intake manifold gasket

Question
Hi! I have a 2001 Hyundai Accent and the other morning, I started my car (the heater was on, I don't know if that makes a difference or not) and I put it into reverse and it made this loud screeching noise from the front of the car. It then happened that same day and the next when I was leaving from work. On my way home my check engine light went on and was blinking rather fast and then went away. Today, the check engine light went on and stayed on...so I went and had the codes read and it said P0507 Idle control system RPM high. We started it up and saw that I was idling at 1500 rpms. So I was wondering if there could be any correlation between the noise and the idling and if you had any suggestions. Thanks so much.     

Heather

Answer
Since your check engine lamp was flashing, indicating a misfire, I'm surprised you don't have a related misfire code (P0300, P0301, P0302, P0303, or P0304) as well.  

Based on the fact that the lamp was flashing and your engine is revving abnormally high, I'd suspect a leaking intake manifold gasket or PCV hose.

You should also check the alternator belt for possibly being loose, causing or contributing to the squealing.

There have also been numerous cases where a defective throttle position sensor causes a high idle, but this typically doesn't result in the P0507 code because the computer is actually attempting to run the engine at those speeds in that case.