I just replace the engine in my 03 Sante Fe 2.4. The engine fires up and sounds good but on initial start up the engine races for a few seconds then slows down but continues to speed up and slow down continuously. I have replaced the throttle bod with the throttle body from the old engine with the same results. No codes are showing.I have also sprayed cleaner through the MAF valve with no changes. What can be causing this. thanks

 

Sound like it could be a vacuum leak somewhere.

 

Or could be IAC valve??
Or bad TPS sensor??