Hey guys, I’m sure this question has been asked before but I can’t seem to find the thread. I have a 1986 Ford F-150 302 efi AOD transmission. My question is how to properly adjust idle set screw on throttle body to factory. I know it was adjusted bc the pervious owner told me he messed with it not knowing your not suppose to adjust it. I know how to adjust the TPS but don’t that screw need to be in the right position before setting the tps? Any help would be much appreciated

 

There is a procedure for setting the throttle plates. It simply says to unplug the IAC and adjust the screw to where the engine just falters and dies. This procedure probably won't work. Other things come into play that are not accounted for. On my 1986 5.0L EFI, there is no setting where the engine will run at all without the IAC.

Here is what I did with success. First, disconnect the battery. This will clear stored memory. With a very clean IAC and throttle plates, I backed off the screw until it no longer contacts the linkage lever. Screwing it in 3/4 turn past first contact with the lever. This is a good baseline setting. At this point, set the TPS to about 0.9v. Very important next step. Before starting, precisely set the transmission TV (throttle valve) If you need help setting TPS or TV cable, just ask.

If improvement is accomplished, drive for a week and see how it settles out. The ECM is capable of adapting to a very limited extent. As processors go, the one in our ECMs is a moron at only 8kb.

EDIT: When these screws get adjusted by the unindoctrinated it is usually to cure a stalling engine. The ECM keeps trying to control the rpm as the screw absolutely does not control idle speed. If you adjusts the screw in, you also tighten the TV cable. This raises transmission pressure, creates harder shifts and, I believe, adds drag at idle when in gear. Only my theory, never saw documentation

 

That less that 1 volt at idle setting is one of the most important things to get right. You usually don't have to worry about that though if you set the screw so the engine barely runs with the idle air solenoid disconnected. And it will take a few drive cycles for it get used to any new settings so don't panic if it throws a little fit the first few times you drive it.