High Idle And Hanging Rpms :(

[Cameron Reyes]

Once you turn on the engine the rpms go to 2,000 and stay there then gradually decrease to 1500 then 1000. And rpms hang while driving. This started happening after me and my brother changed the iac in my 2003 mustang gt conv. It had the check engine light before we replaced the old iac and still has it on, and started acting the way I explained. Any thoughts?

 

[wmburns]

It might help if the actual DTC code were posted. There are 1000's and they each have a story to tell.

However the odds to favor a vacuum leak.

Note, it is normal for the idle to be higher than normal while the motor is warming up. It is also normal for the idle to be higher (1100-1200 RPM) while the car is moving.

Here's some more information that may help.

Troubleshoot IAC idle problems 1996-2004
http://www.stangnet.com/mustang-forums/resources/troubleshoot-iac-idle-problems-1996-2004.13/

 

[Cameron Reyes]

I will post the codes once I get them checked, but thank you for the link!

 

[Moosee1955]

Pop back in the old idle control valve, you might have a defective one. Also check wires going to it. Do you have any intake or Exaust leaks.


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