I installed a new transmission and engine, the car is idling high and once the car warms up, the RPMs go up and down.
Your issue has many potential causes - especially since everything has recently been apart for repair. One thing that comes to mind is that a vacuum line could have gotten left off when you were re-installing your engine. An electrical component could have been left unplugged, too. My best advice is to have a professional mechanic, such as one from YourMechanic, diagnose your problem.
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