So i just put in a used motor. Pretty much everything is new. When its cold started it idles at 1,000 rpm and dosnt go down until u shift into reverse or drive. When u step on the Gas the rpms drop and chugs and finaly starts moving. I set timing and spark plugs are in order. There is no vaccum leaks.
My car has an automatic transmission.
It is very difficult to definitively say what the issue is. Have you had the vehicle scanned for diagnostic troubleshooting codes? If not, you should start there. Due to your vehicle being pre-1996, the method of receiving codes will be more difficult. You should look to your owners manual for that procedure. Hopefully, the issue will have set a code and will make diagnosis a lot easier.
If this is a misfire, its likely a code is pending. Chances are, this is a problem relating to the air fuel mixture entering the engine when the vacuum changes after entering a gear. If you are certain there are no issues with the vacuum, look to the throttle body, fuel injectors, and valves.
If you need some assistance with these checks, consider YourMechanic, as one of our mobile technicians can come to your home to diagnose the misfire firsthand and help you fix it accordingly.
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%