Tx_Sheriff

howdy! my name is nick, i've searched all over for a fix to this problem but cant seem to find one so im trying here!

i have a 1985 Ford F150 Lariat XLT, (6cyl, 302 engine). there is a small problem with the idle, when i start it up, it runs and stay on, but the idle goes low, like its about to shut off, then jumps back up, like its trying to stay on. im not all good with vehicles so i had a friend of mine replace both fuel pumps, new fuel lines, oil change, clean out both gas tanks, and new spark plugs. and still the problem persist. if anyone has a solution to this problem message back, and ty in advance!!!

Bluegrass

Hello Nick, from up north way.
Is the motor a 6 or an 8 cylinder?
A 302 is an 8 cylinder or 5 L, a 6 is a 4.9 L inline.
Well anyway, i'm supprised you have not found out the intake air controller likely is the problem.
It is the idle control that bypasses air around the throttle plate under control of the computer.
It's a device mounted on the throttle body with a electrical connector on it.
Remove this device and get a can of spray cleaner.
Spray the inside good and operate the sliding pintel inside to be sure it is free and all gum is removed.
Take off the intake hose to the throttle body to exposed the throttle plate/s.
Spray clean the plate and open it by hand to get the full area.
Re install everything.
I would reboot the computer by removing the positive battery cable for a few minutes then re connect.
Start the motor with the headlites on and the A/C fan running to provide the worst case load on the motor for a cold start.
Let the motor warm to full operating temperature.
Then if all's well turn off the lights and fan, run about 5 miles.
Stop and restart the motor several times so the computer learns a hot restart condition with the battery recharge load from restarting.
After this, your cold start should go to a high idle depending on how cold the ambient outside temp is and slowly return to about 650/700 rpm and be stable at that point assuming no other issues are present.
All the starts and idle should be near perfect as new.
Hope this is of help.
Let us know how it all works out.
Good luck.

Tx_Sheriff

ok sounds like a plan, its a 6cyl by da way,

but i have another question, what if i dont have a ac at all.
i just got this truck last week, all on my own, and it dont even have the motor for the ac, would this process still work?

Bluegrass

Yes.
I assumed it has A/C.
The load on the motor by the alternator and battery recharge for learning the cold and hot starts is what it's all about.
Just substitute the heater fan on high.
Good luck.

Tx_Sheriff

anyway i can get a picture of what that looks like, having a hard time finding that.