run away idle
 

96 F250, 5.8 auto, no cruise control. mostly before engine is warmed up, idle comes up to about 1500-1800rpm, even if its in gear driving down the road, at the same time purge solenoid chatters. after a while, problem goes away, no check engine light comes on, and has dtc 212 stored. thanks for any help.

Check your idle air control, the tend to go bad. Or you could have a massive air leak some where...Rob

I had a similar problem on my 98 F150. replaced the IAC and that took care of the idle problem. Good luck.

run away idle
 

when we unplug the idle control valve, the engine idles down. so we figured the computer must be comanding it on. thanks for responding.

fixed
 

new TPS took care of it, thanks again