420A Idle Problem

[halfevil333]

Okay I'm having some issues with my idle. When it first starts, it seems to rev higher than usual before coming back down. Then it only idles at about 700-800 rpms. But, that isn't the worst. When I'm driving and I either push the clutch or put it in neutral, the rpms will drop to 700-800 range, then go back up to about 1500. Some times it will stay steady at 1500, other times it will just bounce back and forth between those two ranges 800-1500-800-1500, etc. I have seen them do the same thing but go up to 2k. Sometimes, I will let off the gas and the rpms will not change, the engine just keeps pulling like its on cruise control, usually at around 3k and if I tap the gas, it goes back to normal. The intake is clean , with no buildup or deposits, the throttle cable is correctly adjusted, and both the IAC and Cam position sensor are brand new, as is the PCV valve. I just got through rebuilding everything, top to bottom. I'm thinking it may be MAP sensor? Please let me know your thought on this, because it is killing my mpgs . Thanks in advance!

 

[stayflalfy]

Sounds like a vacuum leak and the MAP sensor is constantly trying to adjust for it.

 

[dsmcrzy]

Yea check your vacuum lines on the back of your intake manifold. Mine have broke there before...