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Discussion Starter #1
I've got an 89 300zx that I just replaced the air flow sensor on. I thought that would fix the problem but now when I start the car up and its cold it idles very badly then dies. If I rev it for awhile and warm it up its fine and starts everytime and runs great. I have haynes manual on it and I think it could possible be a vacuum leak? any suggestions?
 

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I've got no error codes on the ECU. Nissan diagnosed the problem before as being a bad air flow sensor which fowled out some spark plugs. They replaced the spark plugs and I replaced the air flow sensor. The idling problem is still evident while its warmed up just not nearly as bad.
 

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Discussion Starter #5
Another question, if it is a vacuum leak wouldn't I experience some loss in power while I was on the highway? Because its running great on the highway. I also noticed that my voltage meter is jumping from 12 to 15, 12 while I'm sitting still and usually around 15 after its been running awhile.
 

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I have the same problem with my 89. I'am sure its the air regular, which I believe enrichens the mix until the car warms up. Its on the left side of the engine if your facing it. It has an electrical contector and a hose which attaches to the intake. KKing
 

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The only way the air regulator can richen the mixture is by slightly increasing the manifold pressure. The FPR would see the change in manifold pressure and adjust the fuel pressure.
All the air regulator should do is allow a controlled amount of metered air into the plenum when it is cold, allowing a rise in idle speed.
"Metered air" is air that has been through the MAF.
 

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Not as likely as some other things.
It is feasible that the air reg may be leaking at the flange to the plenum but that joint is normally sealed with an O-ring.
The most common failure in the air reg that I have seen is to stay shut at all times and not raise idle speed when cold.
The air reg would have to be physically damaged and cracked in some way to leak air.
There could be a leak in either of the air hoses that supply the air reg, resulting in unmetered air getting into the system.
 
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