Code P1506
I recently purchased a 1998 Ford F150 4.2 v6 164k very cheap. The truck has a hard star especially at cold start it takes three attempts. After it warms up, it still has a hard start, but not as bad and a high idle of 1000 RPM. Exhaust system backfires as well. I purchased a smoke machine. to do a vacuum leaks test. I had ruptured hoses at the back of the intake manifold, and one under the throttlebody easy fix. but I still have a high idle and a very hard start. I have replaced the idle air control valve replaced all the spark plugs fuel filter and cleaned the throttlebody. But no luck. I had a few possibilities on what it could be. I’m thinking coolant temperature sensor
or weak fuel pump or PVC valve throttlebody plate but I don’t wanna buy and replace without any advice. I am really torn on what it could be. Any advice would be great I am so lost lol. Is there a way to adjust idle?

 

Idle speed is adjusted automatically and what you might consider is; without touching the throttle pedal , start the engine and allow it to reset it's idle speed.
It should come down and adjust itself., just be patient and allow it to do it's thing.