95 Grand Am Idle Problem

[gmack221]

I have a 95 grand am 2.3L 4 Speed Auto. Last winter I rebuilt the motor, runs great except at idle. Once you get the RPMs up it straightens out, but at idle its like a big block. Rebuild was complete, new crank, replaced bad rods, new pistons & rings, even new oil pump balance shaft bearings, new crank & rod bearings, old cam shafts, new timing chain set, new oil pump, new water pump, junk yard head, gone thru completely. I replaced the motor on the intake thoratle body (ICA??), even put a new heated vacume hose that goes from the intake to the black breather box above the intake(no one told me they were made of gold $175 dealer part). I've replaced most of the vacume lines, checked to make sure the valve on the brake booster isn't sticking. Sprayed carb cleaner all over the intake & thoratle body to see if I had a leak, no change in idle. I would estimate (since I don't have a tach) that it smooths out about 1500 rpm. Im missing something, experts I need your help! Could it be a ground? All of the work was done by me, could I have a cam shaft off by one tooth? Thanks in advance for any help you can give.

[GTP Dad]

I would check the plugs, coil and wires. Even though you don't show a CEL but it could be firing poorly and causing the idle problem. I would also check the connections to the ignition control module and make sure everything is tight. Also check all vacuum lines as there may be a leak. Check the PCV and make sure it is working and not clogged although I am sure you changed it. The final thing would be to check the fuel pressure at idle. If you have a bad FPR then you could be getting low fuel pressure causing the rough idle.

[gmack221]

Tonight or tomorrow night I will get time to check the plugs & verify im getting strong spark on all 4 cylinders. Im almost positive everything is good there, but it never hurts to double check. I've seen alot of post about the fuel pressure regulator, I will need to figure out how to check the fuel pressure and see if thats it. Thanks for the info, I noticed you didn't say anything about the possibility of me having a cam a tooth off, have you ruled this out due to something I said?

[skibum1111]

If the cam was off by a tooth you would have problems throughout the entire engine range, at idle it would want to shake itself apart, and you would probably be able to get the car to 40mph tops... Found this out the hard way.