I have recently "aquired" an 88 n/a cal spec 300 5spd. does any one know of any cases of cracked collector or intake manifolds????? I've replaced every damn vacume hose in my car, but I'm still running lean, and I know theres aleak because at full throttle the vacum wont hold closed the heater valve and i get a lot of hot air inside (a/c or not) when i race. I have an 85 n/a to but this doesn't happen. I'm in the middle of doing the stanza throttle body conversion(i have an extra complete motor) so I'm hoping the problem will fix itself.

Do you have a way to magnuflux check it?

I dont know much about Z31s though sorry. They were before my education in cars.....

I only know OBDI, OBDII, CAN network (Volvo,Ford) and '66 Impalla 4 drs with 454s.

I've heard of magnaflux but i'm not familiar with it or the process. I've always done my own work so I don't want to take it to a machine shop or engine builder.

It could be many things. The intake manafold was taken off and no gasket reinstalled. Like you said a vaccum hose could be off. Something isnt tight enough. What Ive always wanted to do was take some 2.5 inch bendable plastic pipe and have a K&N on the end of it and elliminate the entire intake and just have a direct line.

I was also thinking of putting a K&N right on the throtel body and let it breath engine air.

I have that same hot air problem in my Z, but I haven't looked into what causes it. I know it is a vac leak, so you're on the right track, but I don't know any details...sorry...if you figure anything out, let me know.

An old way to find vacuum leaks was to take a spray can of eather and go around all the hoses, fittings and the intake manifold with the engine idling..When the engine speeds up you've found the leak. Just be careful you don't burn the barn down.

here's how i've starting fixing mine...
you start by replacing all vac lines under the hood then CAP off the line going from the catanister under the hood to the firewall ( for the heater controls) then go and "race" and see if that fix's it if i does then guess what u gotta get a vacume gauge and test the vac swithes and replace all the vac lines under the dash... its a fun process... if u have a vac switch that wont hold vac then use some wd40 to see if that is the culprit cuz the WD40 will liven up the ruber inside the switch and make it work for a while....

well ya'll, I did the stanza throtle body conversion, and all is well. my heater works fine, and I can feel a real difference. I can do some wicked dry pavement drifts(finally), without working the clutch.

stanza throttle body conversion?

stanza throttle body conversion?
The 1990 stanza has a near identical TB, exept the throttle valve is bigger.
the 300's is 20mm and the stanza is 30mm(so I'm told) go to www.z31.com (http://www.z31.com) for all the details.
p.s. the stanza i got mine from had cruise so the tb works with mine:screwy: