real quick ...5.0 203 k miles owner 10 years been living with this problem now time to fix if possiable...........drive car idle normal then all of a sudden the idle increased like 900 to 1100 rpms all by itself at operating temp. ....pull over shut off ..restart then idle returns to normal....then may pick up again until u shut it off ...basically high intermittent idle /restart goes back...some times could be ok no problem driving for a week or then like today drove 100 miles straight no problems or drove 100 miles got off highway idle high....shut off then goes down...what should i do???the only thing i changed since i owned it is the o2 sen ,temp control, throttle positioned sensor air idle control once like 3 /4 years ago... ...all others are original some pollution device on the rt wheel well with vacuum hoses going to it... don't want to bring it to a mech I can change parts ha! NEED GUIDANCE AND DIRECTION TO START LOOKING ...THANKS

This post has been edited by botz: Feb 2 2010, 09:47 PM

If there is a vacuum leak it will affect the MAP which makes your computer think the thottle is wide open or closed when it is not. 20 year old cars have dirt for rubber hoses and EGR, air to Cat Conv, and climate control vacuum solenoids. Get some EPA rated emmission hose in the sizes on your engine and replace all vacuum hoses and plastic tees. Pinch off the vacuum hose running through the firewall to the heater with a binder clip or vice grip pliers, also the solenoid on the EGR valve and air valve to the cat converter. Run the car and see if the problem stabilizes. The idle may still be wrong because your computer would have false history data, but if the sudden changes do not occur, then you have improved something. Unpinch one at a time the EGR solenoid, the cat air solenoid, then the climate control hose, and see if still stabilized. If not, then hoses and solenoids on the EGR or cat valve or under the dash and on the AC and heater need to be replaced. That is a $10 fix for the hose and $40 for solenoids (do solenoids only if shown to be a problem), if that does not fix it get the engine analyzed at a shop.