showstopper_88220

I have a 99 grand am and we just put a used engine in. I used all of my original stock accessories on the new engine such as, Intake manifold, exhaust manifold, throttle body etc... . We started the engine and it began to idle between 2000 rpms and 3500 rpms like someone was giving it gas and letting off. I changed the Idle control valve, throttle position sensor and map sensor, I also checked the engine grounds. I was told to drive it at least 8 miles to reset the idle control valve, didnt work. I checked for vaccuum leaks and didnt find any. I went to AutoZone and had it scanned, got codes "P0507-IAC system rpm higher than expected" and "P0325-Knock sensor circuit fault". Also when I drive it and its in gear, when you slow down it lunges and bucks forward. I have been racking my brain and stressing soooo much PLEASE HELP!!! I am begging. please, Help me out guys.
Thank you,
Jaymz

GTP Dad

You don't have to beg for help just ask!!! First, it is possible that the knock sensor is bad or the wire to it is not making good contact. Replace it with one from the old engine if you still have it or purchase a new one and replace it. Then clear the code and see what happens. As for the idle air circuit, I think you may have a vacuum leak in the manifold, throttle body or at the IAC itself. One issue with some of the newer cars is that you have to do a case learn procedure so that the computer recognizes the new device. It is possible that your computer is not recognizing signals from the IAC and sending an incorrect idle signal to it. Disconnect the battery cable for about 30 minutes and then reconnect and start the vehicle. This should reset the computer to default and it may correct the issue. If not you may need to go to the dealer or a mechanic to get the idle problem corrected.

john_uhcl

showstopper 88220,

What did you do to get this fixed?

showstopper_88220

I used a can of starter fliud and sprayed around the intake manifold. I found that it was leaking pretty bad therefore causing the map sensor, idle control vavle and tps to not read correctly. I removed the intake manifold and rethreaded two top bolt holes that had been stripped out. I ordered a new gasket and and put it al back together and now it runs fine. Also thank you to GTPDad for the help.