Big Al's Teenage Dream 300zx

[fletch]

5 hours ago, AALAWS said:

 

This is how it sits at the back of the engine - I'm assuming air flow is from right to left so would you remove the hose between the air regulator and the IAA unit or bypass the everything from before the air regulator?

The throttle cables across the plenum seem pretty good - the throttles were closing up nicely when disengaged if that's what you mean?

I think air flows from left to right in that pic. Filtered metered air comes in at the left and goes into the IAC, FICD, and idle screw block and gets into the manifold its bolted to control the idle.

Air also goes into the left of the 'air reg' which is actually the cold start air bleed. It is bolted to a water pipe and has an element in it that is connected to ignition and as it heats up it closes.

Yours could be stuck open. Take it off and block the hoses to see if that helps. A couple of squirts of brake clean should flush it out if it's scabby. Skyline ones fit of you need a replacement.

2 hours ago, xsspeed said:

Chur, had z31 vg30s in mind

I've had grit/crap/whatever get stuck in vvti actuators before which messed with timing and idle revs as was getting stuck, could be worth whipping them out for a flush/clean

Symptoms were high/slightly tough idle like unmetered air was getting by. I fucked around with IACs for so long before seeing it was a timing/vvti issue

This was in an auto and would require heavy breaking at rest to resist rolling fwd as it was loading the torque converter

Yes the vtc actuator moves a piston in the end of the cam and pressures up the pulley. All it does is advance the inlet cam a bit.

they are common to leak with age, and usually causes a rattle from the inlet pulleys.

Don't think it will change the idle rpm tho.