Ok there is a threaded hole under my throttle body opening. What is suppose to be there? I have an L28.

The intake manifold and throttle bodies are common sources of vacuum, and monitoring devices. Check your Positive Crankcase Ventilation system to see if maybe a hose is supposed to connect there. It's a guess.

Frank

Well Frank i checked what the pcv valve looks like for my Z and it's threaded. I think you were right. Never seen a threaded pcv valve mostly push in type. Have worked mostly on GM's. Well I will take care of that. And then I still might need a tps sensor. When it idles it runs around 3,000rpm then drops to 2,000 and continues to surge back and forth. Well atleast she is running right?

That's right, buddy ~ first step is done!

The hole might actually be where the TPS goes? Maybe?

Can we get one of you 280Z guys to run out to the garage and feel under your TB and tell us what's there?

the pcv valve is what goes there in the threaded hole. my tps is there i just think it might be malfunctioning. but first i'll get a pcv valve and throw it in there. also need to tighten down the throttle body bolts so i know i got vacuu there too. i'll keep you posted. thanks Frank for sending me in the right direction.

Well scratch the pcv valve idea. It's on top of the throttle body. I am begining to think that it's just a drain plug. It doesn't seem anything would hook into there. I'll take a picture of it.

Sounds like your missing the BCDD valve (boost controlled deceleration device). Maintains manifold vacuum pressure during deceleration. I think it was a stop gap emission control thing . Block off the opening but I'm not sure if the engine /ecu still expects it to be there,search on classic Z car. Idle problem may also be the air regulator on top of the manifold is sticking . PCV valve is on the side of the manifold if I remember correctly and the hose runs alongside the manifold ? The hose could be gunked up if it was never changed. I will check the PVC hose locations tonight when I get home. Jim

L28 is from 75-83, so what year is this? PCV is on the bottom of the intake on all L28's. A vacuum leak will cause hi idle, not the TPS, or defective idle control stuff like the BCDD, or out of adjustment. Some pics and more info please.

Well Jim that's what was missing. So I plugged it. The idle problem was the maf sensor not grounded. She ha an exhaust leak and was popping and sputtering but she idles. Alternator not charging. And once I press the gas pedal it's like it's sticking cause the idle jumps and doesn't go down. I lubricated everything. Is that the air regulator doing that? This is a 1978.