Code P0505

Good afternoon,

I would try disconnecting and plugging the hose on the brake booster to see if it is causing the issue.

https://www.2carpros.com/articles/engine-idles-too-high

Use some spray such as brake Kleen and spray around the intake manifold and see if the idle changes.

https://www.2carpros.com/articles/throttle-actuator-service

I know you said you cleaned the throttle body really well but check and make sure the throttle plate closes completely. If it is open at any amount, it will raise the idle.

Roy

It closes fully. I've cleaned all around the edges of the plate as well. I just now went and replaced the PCV valve. no change.

Okay, spray around the intake and check the booster as I suggested.

Roy

Okay, so I got a new can of cleaner and sprayed all the way around this morning and didn't really hear any change in the idle. Understanding that part of what's happening is the idle fluctuating a bit on its own. I also pulled the vacuum line off the brake booster last night and plugged that up with no change.

I wanted to mention this as well. When the car is in drive or reverse, it does not seem to fluctuate its idle and hangs out around a thousand whereas when it's in park is revving up to 2400 and then back down to say 14 1500.

Okay, you are going to need a scan tool to hook up to your car and monitor the IAC valve. The scan tool can command the valve to move in and out to verify that it is moving freely.

If that is working correctly, then good chance the ECM is a failure as it controls the operation of the motor.

Roy