Element issues

[Tech56]

Hi, i have a 2004 Honda Element ex that i bought cheap for my son, when I looked at it, it was running high rpms around 3k to 3500 at idle, we towed it home, i have pulled the throttle body, cleaned it throughly still no change, unplugged the iacv and no change, unplugged the map sensor no change, ive searched for a vacuum leak none found, i push the gas pedal and it revs high but goes back to 3k to 3500 rpms, the vehicle has really high miles, ive checked the coolant level and it's good, i checked the engine coolant sensor and it's good, only other possible issues I can think of is an issue with the ECM or somehow maybe it's a timing chain issue, the guy did tell me a shop told him it was either the timing chain or the Transmission itself, but i cannot shift it into gear, with it running so high, any ideas that I haven't tried or any thoughts would be greatly appreciated.
Thank you in advance!

 

[BrutalB83]

Have you tried disconnecting the battery and letting it relearn idle? Worth a try if you haven't. You've already hit on everything else I would have checked.

 

[Briansol]

Does it change when it's cold vs warmed up? thinking o2 sensor going wack...