Bad idling issues, please help
1995 F-350 7.3 Powerstroke
Diagnostic trouble codes:
P0113(IAT Circuit High Input)
P0237(Turbocharger Boost Sensor A Circuit Low)
P1211(ICP Pressure Above/Below Desired)
P0708(Trans Range Sensor Circuit High Input)
So when I start the motor, it will run normal for about 6 seconds. Then the rpm's will jump up to around 800-900 rpms and the idle will become very lopy. When I put it into gear the lope will go away but it will still have that high idle, so the lope will only occur in park and neutral. The high idle/lope will not go away until I shut the motor off. This always happens, its not a random thing. It happens whether or not its hot or cold, and it never smokes at all anytime. The motor has never died on me either. I just purchased the truck about 2 weeks ago with this problem so I'm not sure how long this has been happening. When I bought it, the check engine light was on all the time. The first time I took it to a mechanic, he found that the ICP Soleniod was missing, and so was the Ambient Air Tempenture Sensor. So I bought both parts and installed them both. However when I installed the Injection Control Pressure Regulator, I only installed the Solenoid, as that was the only part that was missing and replacing the internal component is kind of difficult. After installing both of those parts I started it up and it had the same idling issues, but the motor seemed to run better. And now the check engine light only comes on when the idling issues start. When I took it to a mechanic today, he read the ICP while it was running and the pressures read something like this. At startup around 3100psi, after idling issues kicked in it flatlined at 725psi and did NOT fluctuate with an increase in rpm. I have no idea what could cause this, the mechanic told me I should have around 550psi at idle, and it would increase with the rpms. Does anybody know how to fix this? I listed the most recent check engine light codes above.
P.S.- Sorry for the long paragraph, I just wanted to explain everything.