Idle up and down?

[chadz34]

I fixed all my vaccum lines except the one that runs under the plenum AKA the big metal line....Will that make my car idle up and down randomly when it's started, it only does it sometimes, and the TPS is perfect, has been tested. Car has new headgaskets ALL INTAKE gaskets, and was practically looked over top to bottom this is the only thing I can think of?

[grandprixgtp_91]

if your talking about the metal line that runs from the map sensor to the vacuum module on the transmission, then yes. any vacuum leak can cause the idle to go up and down, it will pull in air and raise the idle and the iac will try to lower it, then the idle will go to low, so the iac picks it back up and then the vacuum leak will give it more, throwing it into a hunting cycle.
Jake

[chadz34]

if your talking about the metal line that runs from the map sensor to the vacuum module on the transmission, then yes. any vacuum leak can cause the idle to go up and down, it will pull in air and raise the idle and the iac will try to lower it, then the idle will go to low, so the iac picks it back up and then the vacuum leak will give it more, throwing it into a hunting cycle.
Jake

I guess that's the one. It's a 50$ line from GM,,,,,

[grandprixgtp_91]

try fixing it with rubber vaccum line first. see what happens. you could also use brake line , it bends easy by hand.

Jake