'75 280z runs rich - need help

[jsb5717]

I'm a new and first time "z" owner. I just bought a 1975 280Z with a rebuilt motor. The car runs very well but runs rich and is getting lousy mileage. Since it has fuel injection I don't think there are any mix adjustments, only idle speed. I can't seem to find any vacuum leaks. Any thoughts as to what I should be looking for?

Thank you...

[k3smostwanted]

Originally Posted by jsb5717

I'm a new and first time "z" owner. I just bought a 1975 280Z with a rebuilt motor. The car runs very well but runs rich and is getting lousy mileage. Since it has fuel injection I don't think there are any mix adjustments, only idle speed. I can't seem to find any vacuum leaks. Any thoughts as to what I should be looking for?

Thank you...

is it a turbo motor?

air filter dirty? MAF? may need tuned? faulty ECU?

[jsb5717]

Originally Posted by k3smostwanted

is it a turbo motor?

air filter dirty? MAF? may need tuned? faulty ECU?

No turbo, new air filter, new plugs, wires, rotor, cap. I wondered about the ECU. Is there a way to test it?

I don't know what "MAF" is.

thanks...

[k3smostwanted]

Originally Posted by jsb5717

No turbo, new air filter, new plugs, wires, rotor, cap. I wondered about the ECU. Is there a way to test it?

I don't know what "MAF" is.

thanks...

Mass Air Flow Sensor...it is a sensor on Fuel Injected cars that measures the incoming air charge.

how do you know its running rich?

i dont know of a way to et the ECU

[jsb5717]

Originally Posted by k3smostwanted

Mass Air Flow Sensor...it is a sensor on Fuel Injected cars that measures the incoming air charge.

how do you know its running rich?

i dont know of a way to et the ECU

I can smell it (perhaps that lean). Anyway, there's too much gas in the mix. The larger issue is the poor gas mileage. I'm not sure what standard is but I'm guessing it should be closer to 20mpg rather than 10mpg.

thanks...

[billszcar]

The mas air flow senser can be a bugger! it is the thing thats in between the air filter and the throttle body. it works by the air flow threw it. the more the air flows threw the further the flap oppens in side. the senser it self runs on a small strip of tape. like the one on your creadit card. as the flap oppens it swipes the tape and sends a signal to your computer to tell it how mutch fuel to give the injectors. they get dirty and tell the computer the wrong thing. now if you clean it you can possibly make it worse. Make sure the cleaner you use is mafs compatible so you don't destroy the tape! hope this helps you. good luck
Oh by the way I am a Z FREAK! Have 3. 76-77-78!

[datsun62]

Two of the main causes of running rich on a 280z are fuel pressure too high or a bad conection on the fuel mixture sensor
Fuel pressure should be around 30 psi engine running, when the fuel pressure regulator goes bad your fuel pressure normaly goes up and causes your engine to run rich.
There are 3 sensors on the front of the thermostat housing below the radiator hose on the front of the engine.
one is just a small nipple with a single wire it controls the tempeture guage.
The other two sensors look simular one is taller than the other,with a injector
type electrical conector.
The taller one controls the cold start injector.
The shorter one controls basic fuel mixture.
It is variable restior,when the car is cold the restance is high making the engine run richer, as the engine warms up the restance goes down causing
the engine to lean out and run normaly.
What happens to make it run rich is you get green corrosion on the conector and sensor giving it a bad conection or no conection at all and makes the engine run rich.
With a bad conection the computer senses high restance from the sensor
and adjusts the mixture too rich, this is the first thing I would check.
you can try to clean it up,the best thing to do is to replace the sensor and
the conector, you should be able to get both at most auto part stores.
look in your book for the proper sensor name or bring it to them so they can
match it up with the new one.
Just a word of warning don't do this when the engine is hot.