Hi everyone! I've lurked around here for a while, and I figured it's time to register since I'm stumped... My son has an 04 cavalier 5 speed. We had to swap motors due to a timing chain going south. The motor we got came out of an 03 Malibu. After wrestling it in place, we finally went to hooking everything back up and ran into a few snags. I had to change the crank position sensor and the connector that goes to it. Fuel rail carried over from the old motor, but the intake and throttle body are from the "new" motor. My problem comes in when we try to start it. It cranks over fine, but as soon as it starts running, it acts as if the throttle is held wide open. The throttle blade stays shut, but it still runs the rpm through the roof. I tried unplugging the idle air control and throttle position sensor independently and at the same time with no change. Code scanner doesn't pull up anything. I'm pulling my hair out. He needs to get his car back on the road so he can get back and forth to work. Please help me!!!
Could I have wired the crank sensor wires backwards? Would that cause it? Sorry for the long first post.

Sounds like a vacuum leak. Make sure all of the vacuum lines are hooked up or plugged and any unused ports are plugged.

Thanks for the quick response! I plugged the pert just below and to the right of the throttle body and the one that runs to the brake booster. The only other one I'm aware of is the one right above the throttle body that had something attached to it. Any other places I should check?