I just installed a new iac valve and it fixed my idle when the car is warmed up and loud noise is gone but when I start the car up it goes up to 2000rpm for a couple seconds then down to normal is that normal just bought the car so I don't know what's normal

 

If the Battery has Not Been Disconnected Since IAC Install I Would Disconnect for About 15 Minutes and Reconnect. This Will Reset Everything and Then Drive it a Couple of Days To Set DRIVE CYCLE. As Far as The Rev I would Not Be Concerned at the Moment. I see By Profile Car is 98 GT for Other Owners To Comment on Their Start Up. Does it Always Do The Rev or Just on Cold Start.

I Post the Drive Cycle Info Just to Show The Varied Things That Need To Happen to Get Everything Settled. You Can Just Drive Normally for a Few Days and Everything Will Come into Play with out the Cycling Procedure.

My 02 Harley Truck Does The Rev Thing When Cold For Sure. Don't Remember about When Hot. Just Don't Think About it!

https://www.totalcardiagnostics.com/...-driving-cycle

KC

 

At all start ups I will disconnect the battery I was trying to get the sensor to learn but I'll try this first thanks

 

While You Are At it and Since You Just Got It. Some Fuel Injector Cleaner Might Be Wise To Put in During Your Drive Cycle. Techron Seems To Be The Most Popular!

https://themustangsource.com/forums/...leaner-493878/

KC

 

Did a Little Test For You as I Needed To Run an Errand This Morning. Dead Cold Outside temp 60 Degrees. Cold Start Flash to 1800 Rpm For a Few Seconds Drop to 1200 and After a Few Seconds Tapped Throttle and Dropped Some More But Not To Hot Idle Neutral Which is Usually about 750RPM.

After Errand and Returning Home Tried Hot Start Flashed to 1800 and Immediately Dropped to Normal Idle Speed. Just an FYI Reference. Similar Engine Management Era Programming.

KC

 

I did disconnect the battery last night today when I start it up needle goes swings to 2000 drops right down to 1800 so it looks like it's normal still need to complete the drive cycle