Every once in a while my 2003 f150 will idle funny. It will go up to about 1500rpms then drop down to about 300rpms. then back up and back down. it will do this til it stalls. I will restart it after a very short while and it will run fine. It has done it waiting in line for gas, drive up bank teller or pulling into a parking spot and putting it into park. Any ideas? Thanks

 

CHeck out the sticky section but I'm assuming pcv, iac, vacuum leak, dirty maf could be a lot of things

 

But what is an iac, or a maf. New here and not familiar with some abrieviations. Thanks

 

Iac=idle air control, maf= mass air flow

 

Like I said check out the sticky section maybe someone can link It I can't on my phone but ibd2328 did an Awesome write up on all these that will help you learn diagnose and repair to an extent