have a 97 aerostar engine started to shutter couplle days ago so i through it on the diagnostics and gave me the code p1390 wich is P1390 Octane Adjust out of Self-Test Range where would i find this sensor and what can i do to fix this problem thanks

 

Welcome to FTE!

It sounds to me like one ot two things: (1) Someone may have pulled the Octane Adjust Shorting Bar on your truck. When this is done, it's usually to help keep excessive spark knock (pinging) under control, or (2) You have a problem with that circuit, like for example, a short or open caused by a chafed or broken wire or a corroded connector.

Ford manual says:

P1390 - Octane Adjust (OCTADJ) "The octane adjust is software activated in the powertrain control module, used to retard spark timing by three degrees. The hardware shorting bar has been removed."

This thread will tell you more about the OCTADJ:

https://www.ford-trucks.com/forums/s...d.php?t=162016