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Discussion Starter #1
In response to the e-mail you sent me earlier.
1) If you don't have it already - get at least a Haynes Manual for your car. The Nissan service manual would be better but it's $73 vs. $13 for the Haynes.
2) 280Z's have AFM's, not MAF's. That is why the parts guy couldn't find it. It's located right behind your radiator frame on the drivers side, just downstream from the air cleaner. They cost about $250 new so don't arbitrarily change it out. It probably is not the cause of your problem.
3) Check out your cold-start systems first which include:

a) Air Regulator: It sits on top of your intake manifold and has about a 3/4 OD hose going in and out of it along with an electrical connector on the front of it. Check out the connector. Get yourself a can of elecgtrical contact cleaner from your local parts store and clean up the contacts. They are sure to be at least a little corroded. If you are running rich at start-up it may be stuck in the closed position. If you are still running rich after the engine is up to temperature then this is probably not the problem. It's job is to add estra air during cold start-up when all the fuel enrichment systems are activated. If it fails in the closed it will cause cold-start problems but not any running problems once the engine is warm. If it fails in the open position you will cold start fine but then go lean once the engine warms up and then it will quit on you. If your plugs are truly fuel fouling then this is not the problem.

b) Engine Temperature Sensor: This is the smaller of the two-wire sensors located on the front of your thermostat housing. When the engine is below about 70°F it sends a signal to the ECU that cause it to increase the fuel pulse duration of the injectors - thus enriching your mixture. If your sensor is bad (unlikely) or the sensor connectors are corroded (possible) then the ECU thinks the engine is cold and socks the fuel to it. Use the contact cleaned right at the sensor AND locate the bullet connectors that connect to the wiring harness about 16 away from the sensor and clean them too. The bullet connectors corroded on me and you wouldn't believe the clouds of black smoke that came out. When you find the bullet connectors, jumper them across. That will make the ECU think the engine is warm and see how it runs then, If no change then that is not your problem. If it runs fine after that then your poblem is probably in the wiring/connectors and you should probably just replace them.

c) Thermotine Switch: This is the larger of the two-wire sensors on the front of your thermostat housing. It tells your cold start injector to fire for cold start-up. Clean all the connectors on this like with the engine temperature sensor.

d) Cold Start Injector: It is your 7th injector and is located on your intake manifold - follow the fuel line. It is controlled by the Thermotine switch. Sometimes it sticks in the open position. You can tell if you have fuel in the intake manifold under it. Remove it and look. Also, while it's out, block the hole in the intake, hook it up so it fires into a plastic container and start your car after it has warmed up - if it is still injecting fuel and you've ensured the thermotine circuit is good, then it is bad and should be replaced.

All these components cost $80-100 each so testing is the better approach to random changing out - unless you have a supply of very cheap used parts..

After you do all this - use the supplement section in the Haynes manual and check out your EGR valve and BPT valve.

Hope this helps,
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