Rough Idle on start up...

[gomer23]

On my last tank of gas i only got 18-19mpg, shifting at 3k rpms when i drive and not beating on it. The engine is a rebuilt KA24E with about 13k miles on it. I check my MAF and regrounded it and it fixed my idle issue once the car is warm. But when I first start my car in lets say a few hours is idles really low, like 400-500 rpms like it wants to die. But after i rev it a few times it runs fine. I have checked the resistance on the coolent temp sensor and that seems fine, and my MAF now should be all good. My TPS is also set to where it should be.

So what does that leave me with to look at that would cause a rough idle on start up? Thanks for any help.

[gomer23]

bump

[Nismo_Freak]

Hmm... just a hunch but check the voltage on start-up. Might be a worn alternator.

You can temporarily raise the base idle.

[gomer23]

Well, I did check the alternator and that is fine. I also check the o2 sensor today, i got a voltage of about .16-.2volts while it idled not sure if that is what it should be or not. Also I unplugged the water temp sensor while the car was running and the idle jumped up to like 2k rpms for a sec then came back down to where it was idling before. Should I do that or does it mean the sensor could be bad?