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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
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We have a 2oo4 Chevy cavalier that we had to replace the

Customer Question

We have a 2oo4 Chevy cavalier that we had to replace the motor in. The replacement motor came from a wrecked 2003 Malibu. It came complete with the intake and throttle body. We put it in and when we got it started, it runs up like you have the throttle wide open. We have plugged all the vacuum ports we can see and nothing changed. We also covered the throttle body opening and it still runs away with itself. Tried unplugging the IAC and TPS sensors (separately and together) with no change at all. The only thing we have done to it is change the crank position sensor and the plug for it, but I'm fairly certain that we got that right. We definitely need help!
Submitted: 11 months ago.
Category: Chevy
Expert:  kalamykid replied 11 months ago.

Please give me just a couple of minutes to look a few things up. IN the mean time Did you keep the old engine that you took out of your car?

Expert:  kalamykid replied 11 months ago.

I need to know if you have the old iac?

Customer: replied 11 months ago.
It came out of either an 03 or 05 Malibu. It was wrecked in the left front. I know the year was one side or the other of the model year of the cavalier we have. I didn't know the malibus came w 4 cylinders as an option. Unfortunately we took the old engine back to the salvage as a core. I'm wishing that I had kept it for spare parts now. Would the IAC matter if we plugged off all three vacuum ports and plugged the throttle body off? It still started up and ran up to red line. I pulled the intake off and looked it over. No cracks or holes that I can find.
Expert:  kalamykid replied 11 months ago.

What I need you to do id start the engine and unplug the iac and then shut the engine off. Then pull the iac out and tell me if the plunger is all the way in or all the way out.

Expert:  kalamykid replied 11 months ago.

The iac may be stuck in the full open position" all the way in" and not closing off causing the engine to run wide open.

Customer: replied 11 months ago.
I saw it move when I turn the ignition on and off. It doesn't appear to be stuck. I had to come in for a sec so I'll have to run back out in a sec. So the motor can run if you cover the intake with a cap? Shouldn't it be impossible for it to get air to run?
Expert:  kalamykid replied 11 months ago.

If the iac is not closing it will still run even if you cover the throttle body. The iac lets air in to the intake past the throttle body.