Finished swap but idle bobbing issues have surfaced

[180fan]

Hey guys, I've just finished my swap and everything else seems fine but for one problem I've encountered. It's my idle. It bobs up and down. When I start the car with a cold engine, it starts at 1500 then sits there for a second, dips to 500 and rebounds to a little over 1k and yeah. Any ideas guys?

thanks

[dj_lennon_franz]

motors usually idle higher when they are first started...its a cold motor...when the motor first start it usually always revs higher for a second then the revs drop close to normal idle....try adjusting you idle screw located on your throttle body

[180fan]

Yeah that's normal, but mine is bobbing, as in a second later it dips to 500 or lower and jumps back up to 1k+ and back down again and oscillates.

[dj_lennon_franz]

i get that sometimes with my motor...but only when the RPMs are set past 1600...im not sure what causes this though

[toledo240]

let your car idle for a little. and llet the motor warm up out of cold start. check your rpms then. usually you want it around 600-850 rpms. if its not. take your tps sensor off your throttle body and adjust your idle control vlave located on the intake manifold you can see it in the middle of the manifold its like a plastic screw. Ajust it left or right till you get it right and plug in the tps sensor again. it might take 3 or 4 tries. if this doesnt work you might have to take te idle control valve off and clean it with carb cleaner, thats what you got to do if it still jumps

[s13sr20chris]

try running an extra ground from the maf to good ground. nissan has never been to good with grounds. look for vacuum leaks. got stock pcv/breather sys?

[180fan]

Found the problem. It was a loose vac hose, the big one next to the intake was slightly loose. Pushed it and damn stable.

I've got alot of grounds just for experimentation. Daisy chained from the battery to alternator, block, head, transmission, firewall, intake manifold, and throttle plate. Just wondering if it'll make a difference over my buddy's similarly setup system without those grounds.

thanks for the help guys. mucho appreciated.

[s13sr20chris]

good idea with the grounds. you know those old nissans you see driving around blowing black smoke(just a little). prob half are just cars with bad grounds. the maf is the first prob you have with bad grounds. .1 v of voltage drop on the maf circuit would fog up the place.