Hey everyone.
I am trying to trouble shoot 2 problems. Maybe related and may not. First is when I start the truck it will jump to 2000 rpm or over, Then drop, recently is has dropped so low it stalls. I can get past this if I start it and quickly put it into gear. The second is when I come to a complete stop. It will occasionally slip out of gear. I can't find a rhyme or reason to it. It seems to be random. If I rev then engine it will jump back in gear. But it is making the truck very unreliable when I need to stop and go.
Thanks in advance.


1990 f150 Lariat 5.0
automatic

 

For the RPM issue remove the IAC valve and clean the carbon out of it with carb cleaner. Make sure the shaft will move and doesn't stick. For the tranny issue, assuming the fluid level is correct it sounds like the pump is starting to go or there's an internal leak.