Engine Idles at 4000 RPM at start

[90bronco302]

Just swapped in a 5.0 5 speed engine and tranny, but now everytime we start the car it revs right up to 4000 RPM and stays there. No idea what is causing this problem. We checked the TCP, MAF, salt and peppers, IAC, etc. but still happening. Can anyone help me with this? I have a video, but I can’t post it.

Did you find a answer to this problem?

 

[red5.0fox]

Did you find an answer to this problem?

If I remember correctly I believe it was the RPM gauge was messed up. Falsely showing 4k rpm