I think when I did it I lightly pried on the open slot behind the joint with the bolt removed. When I rebolted the new one back in it closed it back up..

See I was assuming dirty or bad idle air control motor but with popping in the cat makes me wonder. Hopefully I read this right just skimmed a but but did you reset the computer after engine swap? (consists of removing battery and holding foot on the brake for half a minute)


Battery was ...

Due to a bad RMS we decided to pull the motor and tranny. All went well and I decided I would perform the following while it was out.

Replaced
RMS
Oil pump and pick up seals
Main tranny seal and axle seals
S1 and lock up solenoid
Timing belt and several tensioners/pulleys

All went good putting it ...