I Need Help with my 76 280z

[Zfanantic]

Hi everyone i need help with my 76 280z im haveing trouble smogging it and no one where i live knows about them so if someone could just let me know if they know what i could check or look for it would be greatly appreciated thanks

[IdahoKidd]

You will need to be much more specific. What issues caused it to fail the smog test?

[Zfanantic]

The guy said that did the smog said that it was running to rich.

[IdahoKidd]

Have you gone through all the obvious? New plugs, check air filter, check timing, etc?

[Zfanantic]

yes i have i did a full tune up set the timing everything. and i just dont know what else to do?

[Pomorza]

When you fail smog (at least in Arizona) you get a paper that tell you what readings your car (Z in you case) is running and what it should be at. If you have said paper it would be nice to see the numbers.

But in case you don't. The 280z fuel injection system is fairly easy to understand really. Nearly all the cases I've had of my car running rich was due to the air meter. Basically the air meter is a huge flap in the intake box. When air enters the box the flap moves sending an electrical signal to the computer telling it how much air enters the engine. This reading is used by the computer to adjust the fuel curve. The air meter can be adjusted to allow more or less air to enter the engine at a given time.

Now I'm not saying this is your problem but it is a possibility. Here's the bad news though. Although one can adjust the air meter by ones' self the only way to properly do it is to have an exhaust analyzer. Without one your really kind of shooting in the dark. I personally would take it to a mechanic that knows something about Z's. It doesn't have to be a specialist but somoeone that knows what they are doing.

Hope that helps

Jan

[sblake01]

I have to disagree with your assesment there, Jan. Fuel mixture can be rich because of not getting enougn air in the mixture but also because of getting too much fuel in the mixture. Adjusting the AFM will do nothing about the latter condition but overcompensate. Personally, I wouldn't touch the air flow meter adjustment until I looked a few other things. I do have Gunson Gastester which is an exhaust analizer but I've been around these cars a long time and I've rarely foutd the AFM to be at fault. Keep the AFM clean but don't mess with the adjustment until you checked a few other things such as leaking injector(s), leaking cold start valve, bad thermotime switch (allowing the cold start valve to introduce extra fuel into the system), a malfunctioning or incorrect water temperatre sensor, improperly adjusted or malfunctioning throttle position switch, a bad catalytic converter, improper fuel pressure, the list goes on and on. Screwing with the AFM adjustment is bad advice and could just make things worse if it isn't the actual problem.

[Zfanantic]

well thanks very much guys.....i was told by a few people that the cold start valve would be the problem so i guess ill start with that and go from there....thanks again Joe

[Pomorza]

I have to disagree with your assesment there, Jan. Fuel mixture can be rich because of not getting enougn air in the mixture but also because of getting too much fuel in the mixture. Adjusting the AFM will do nothing about the latter condition but overcompensate. Personally, I wouldn't touch the air flow meter adjustment until I looked a few other things. I do have Gunson Gastester which is an exhaust analizer but I've been around these cars a long time and I've rarely foutd the AFM to be at fault. Keep the AFM clean but don't mess with the adjustment until you checked a few other things such as leaking injector(s), leaking cold start valve, bad thermotime switch (allowing the cold start valve to introduce extra fuel into the system), a malfunctioning or incorrect water temperatre sensor, improperly adjusted or malfunctioning throttle position switch, a bad catalytic converter, improper fuel pressure, the list goes on and on. Screwing with the AFM adjustment is bad advice and could just make things worse if it isn't the actual problem.

Joe I agree with everything you said there. I was just talking through experience as the last time my Z ran rich I check all the above and found that someone had screwed with the air meter and basically made it useless. I must apologize on missing all the steps and misinforming but again it happened to me and that's what it was.

Jan

Edited January 13, 2010 by Pomorza

[sblake01]

Joe I agree..........

He's Joe, I'm Steve... Edited January 13, 2010 by sblake01

[Pomorza]

Sorry Steve I don't know everyone here yet. :stupid:

[Zfanantic]

well both very helpful i appreciate it thanks very much