Need help, s13 idles weird.

[wanganss13]

So my 240 idles fine when I first start it up but when it warms up it starts going up to 2000 rpms and down 1500rpms on its own and wont stop. I was told that my battery could have gone bad so I changed it and still the same, Then I thought maybe my MAF went bad so I changed it as well and still the same. I don't know what the heck is going on, can you guys please help me out and give me some ideas that could be the problem.

[blacksrjdm]

Obviously the battery wouldnt cause a jumping idle symptom, but the ready for it....

IDLE air control motor/valve would be the first place i would start. If that doesnt fix it, then you have a simple vacuum leak.

[dana541]

be shure to check the simple things first before you start throwing parts at it.check for disconnected vacum lines,unplugged sensors or anything out of the norm.

i had the set screw come loose on my cap a while back,it caused it to rattle around create some very strange idling .this drove me crazy for a few months and i through some parts at the engine that i didnt need to.lesson learned for me,check the simple stuff first

[snowyred180]

The IAA valve on these cars malfunction all the time. It's at the back of the motor on the intake side. It's the piece with the idle adjust screw. Search the site for pictures. It's 4 bolts, a vacuum hose, and some connnectors to take out. New is $200 at Nissan, and the part they gave me had the wrong connectors on it. So try a junkyard.

Otherwise, check vacuum hoses. Mine had a bust vacuum valve at the complete back of the motor. I wouldn't have even noticed it, but swapped the engine and notcied the broken valve.

[megaderk]

i have this same issue.still havent gotten around to fixing it....

[wanganss13]

Sweet! I checked for any hoses that might have come off and every thing was good, but maybe one or some have a crack or maybe that IAA valve thing. I realy do appreciate all the reply's, Thanks again. I wont be able to get around to this till sunday, when I take a look at it I'll let you guys know what happens. Thanks again every one.