Simple IDLE setting Issues?

[acermcgraw]

Hi there everyone this is my first post as i have been able to find all of the answers to questions i have had on other posts. This forum has been a real life saver.

One to my issue.

I have a 78 280z and i just bought it to do a restore on it, it has been sitting for about 5 years, was not prepared correctly for storage and i am now replacing hose after hose and part after part.

I have done full tune and brakes and a few other things and the idle has just been getting more and more stable until yesterday morning.

I went outside to warm the car up and it would start but wouldn't hold idle and would die shortly after starting. When i did finally get it started (after i would hold the gas and let it warm up a little) it would only idle roughly at about 500 rpm.

I then smelled gas very strongly (i have smelled a faint gassy smell ever since i got it ) and popped the hood, one of my injector hoses was leaking badly so i replaced it thinking i solved the problem but when i went to start it again it did the same weird idle.

I looked in the Chilton and found the idle speed screw up by the air flow meter and began to turn, the idle barely got to 700 rpm with almost ten turns of the screw and i was off to work.

But now the car has warmed all the way and unless i am completely stopped my idle is up at about 1500 rpm (which i am sure is the idle screw finally doing its job) but when i stop at any light or in traffic the idle drops back down to about 750.

So i guess my question is there two idle screws like one drive idle and one curb idle or what, i am really kind of stumped here so any insight would be very helpful. thanks so much .

[KDMatt]

Hey there, welcome to the CZC online community. 'Sorry to hear you're having some trouble, but we'll do our best to get this worked out with you (and our success rate is pretty good too!)

Okay, to answer one question, there is only one idle screw, and it's the one I'm assuming you found (on the throttle body). There is also an auxiliary air valve that adds extra air into the manifold when the engine is cold, but this is not adjustable.

Before we dig too deeply here, it'll help us to know what you've done so far with the car that way we have a point of reference, because a bad idle can be affected by so many things.

First, I would examine the following things:

Spark Plugs/Wires/Dizzy Cap/Rotor

Vacuum Hoses

Ignition Timing

Electrical Connections (to fuel injectors, water temp sensor, Air-Flow Meter)

Also ... fluids? ... I'm assuming you've changed everything (gas, oil, coolant, brake fluid/clutch) ... but I feel like I should ask, because you're obviously not going to get this thing running properly with bad gas or bad oil (or both).

You may also want to look at your fuel lines, or the status of the pump and tank. Your gas-smell may also be an indication of a leak, and in the fuel injection system on these cars (or on any FI car really) maintaining adequate pressure is critical, so even a minor leak can make a big difference.

[DeesZ]

If you've been starting the car frequently without 'running' it, it could be the most simple thing, and that which KDMatt mentioned first.... spark plugs. Pull them and check to see if they are fouled..... Knowing what they look like will also help everyone diagnose. Keep us posted.

[acermcgraw]

Thanks guys i appreciate the responses, I have changed every fluid and have driven the car on a daily basis for the last two weeks.

I have changed the plugs ,wires, cap, rotor, and tons of brake stuff.

When i replaced the fuel injector hoses the fuel smell went away.

[acermcgraw]

Also i pulled the new plugs and they are clean as a whistle., i also pulled the air filter and changed that.

[sblake01]

Does your car accelerate normally? You might have a problem with your BCDD if the idle hangs at 1500 and then drops to normal when you're stopped. That or a bad altitude switch (if it's a California car) can cause that problem. Been through that with mine. Do you have a FSM?

[acermcgraw]

it accelerates and drives perfectly as far as i can tell, i was having issues where it would hang at 1500 and i unplugged my altitude sensor (California car) and that didn't make a difference so i took off the dash pot all together.

It had no electrical or vacuum connectors so i figured it was just malfunctioning and everything ran fine for a while after that (better even).

[sblake01]

I don't quite get your answer. The dashpot and altitude switch are two different things. Both can have an effect on your idle speed. The dashpot can be adjusted and to some extent, so can the altitude switch.

[acermcgraw]

im sorry what i meant to say was that i found the dashpot to be the throttle hang up in that situation and removed it solving the problem, i no longer have the rpm hangup.