i am stuck on how to adjust the idle on my 93 f150 5L xlt i have been going through a lot of different adjustments like my main power screw and i've got it running really nice but idling really high at park @1000-1100 but in drive it goes down to 900-850 and tries to cruise at like 10-15kmph at least and the power is imediate like if i take it out of park and just let go of the brakes it jumps and spins the tires real quick and i'm sure that it is just the high idle... i just don't know how i can adjust the idle without killing all my power....
i did try to adjust the idle down with the "power screw/ throttle stop" and it runs really rich and and almost dies because of how much fuel it is being fed, when i start it with this adjustment really low it rolls coal but fires up really quick... i am curious if there is anything i can adjust to keep the air fuel mixture i have set but idle lower. thnx
cheers

 

There are no user adjustments for idle speed on an EFI motor so you have some bigger problems. Have you pulled codes yet?

 

Sounds like you have a vacuum leak.
Check all your plastic vac lines and rubber hoses... they get brittle with age and heat.

 

both times i have tried it has given me no codes .......
but some guys at my local 4x4 shop say that it is fine and i am just being a little picky with an old truck lol but i don't like wearing down my 31's lol so i was hoping that there might be a way of making it idle down maybe by adjusting my throttle stop and maybe the at the fuel pressure regulator... or even swapping a part that is designed to make it idle lower like a temp sensor or tps ???? justr hoping lol

 

and i have made a few changes to my intake that allows more airflow... and that in it self might have given me the extra rpm i don't want but it also gave me quite a bit of extra top end....
and i solved my rough idle by replacing a lot of vaccum line lol

 

Unplug the electrical connection from the idle air control valve and see if that slows the engine down.

 

I'd also suspect the IAC valve.

The stock air cleaner and intake setup flows more than enough for a stock or slightly modified motor. There is really no need to modify any of it.

FYI: Next time you create a thread you may receive more responses if you title the thread accordingly.

 

Running really rich? Try checking the FPR. If you pull the vacuum line off and fuel dribbles out, you know it'd bad.

 

When you say you got no codes do you mean you got no response at all from the computer? If so that in itself says something.... you're either not doing it right or you have wiring or PCM problems.. you should at the very least get the 11 or 111 all clear codes.

 

the obd 1 scanner i used gave me a loading bare and said in bold letters no codes found... and i will check the fpr because it does run pretty rich at start but at the current idle it is fine.. and i did unplug the iac while it was running and the idle dropped to 900 rpm's but then started to run reeeeeeeaaally rich -_-

 

What scan tool was it?

 

that is a good question.. it wasn't mine but the local 4x4 shop had one that they loaned me lol

 

thnx guys i found that my issue was the IAC and am looking to replace it
cheers