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.
Have a car question? Get free advice from our top-rated mechanics.
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%