Running Very Rich

[jwc4248]

My sons 81, 280 wouldn't start so I shorted across the relay and it started. It immediatly began running extreamly rich, missing wouldn,t rev beyond 3,000. The car didn't make it 1 mile before dying. I at first suspected the fuel pressure regulator and changed it. No luck. I then in the assumption that I damaged the computer changed it same result no luck still rich. The O2 sensor is fouled but seems ok and is not shorted out to ground. I am out of Ideas and do not want to just throw parts at it PLEASE HELP!!

[2ManyZs]

Try unplugging the cold start valve (injector) in the front of the manifold and see if it makes any difference.

It could be a water temp sensor or the air temp sensor that is causing it to think it needs to enrichen the mix (it acts just like an electric choke)when it really doesn't.

BTW, the best thing I can tell you to do is buy a Factory Service Manual. It will give you numerous tests to do to determine problems in the Fuel Injection and Ignition. These systems are a bit primitive by todays standards, but they can get quite complicated when trying to track down a possible electrical problem like this....

[carguyinok]

From the sound of things I would look at air regulator. It sounds more like a lack of air. This is just a shot in the dark.

Adjustment of the air\fuel mix can be made at the air regulator.

You will find this screw under a small rubber plug on the motor side if the sensor. clockwise is rich counterclockwise is weak.

Hope it helps.

[2ManyZs]

If that fails, start with the basics....

Air filter not clogged, air flow meter operating properly, fuel filter, etc........There could be any one of a dozen reasons for this problem:disappoin

[jwc4248]

I unplugged the cold start injector and blocked off the fuel supply to it. No Luck. I then checked the water temp sensor it has resistance of 57 ohms, the conector was corroded so I cleaned it. No Luck. I checked the air temp sensor it has resistance of 80 ohms. I then checked the Air Flow meter. It has 75 ohms resistance and moves smothly for about 1/2 to 3/4 inch to 290 ohms then goes dead and opens and closes intermitently the whole distance. I am not sure but this might be it?

[2ManyZs]

Sounds like there might be something in the AFM. Take the plastic cover off the side and check to see if there is any corrosion on the rheostat. You might also check the connector on the side as well.

Seems like I just saw an AFM on Ebay for a ZX... you might want to look and see if you can buy a used one for cheap and try that, never hurts to have an extra like that around if it doesn't work.....

[jwc4248]

I took of the plastic cover and didn't see anything right off, I will maybe spray it with some electric contact cleaner. I will look on E-Bay and shop the local pick and pull. Thanks!

[Daniel]

WOW, You've gone deep!! If you where to pull back to the basics.Is the fuel filter new?Is there water in the fuel? Remember if you let it sit ,good fuel will rise the top and bad fuel sediment will settle.Boy ,F.I. sure took the fun out of it!! O.K. I'll quit pretending I have a clue. Daniel

[2ManyZs]

That's the reason one of my first ideas was to get an Factory Service Manual. It gives all the resistance values for all the sensors, and tells how to test them through the plug at the ECM and which pins to use to do the checks....anything is better than "guesstimating".....

I'm a bit stumped when it comes to FI because I'm not a good "electrician", those little electrons are harder to find than those elusive "nauga's" for interior parts.....

[jwc4248]

I finally found a factory service manual online and ordered it. It will hopefully be here by the weekend. With;out it I am just shooting in the dark. I did pull of the air pipe behind the Mass Airflow Meter and it ran fair enough to remove from the shop.It would rev and idle but at about 1100 rpm.

[sjcurtis]

the air flow meter problems can manifest them selves in many ways. From what you have described you have rich mixture induced by a weak air metering flap spring, if you remove the large black plastic cover you will see a phillips screw locking a piece of black plastic tensioning the return spring, in your situation you need to increase spring pressure by about five increments this will lower the fuel rate and increase air percentage. You need to try a changed setting to check for change, then adjust the pressure on the spring to obtain the mixture rate you need.

If you pull the airflow meter apart and adjust at this level. I recommend you spray lube in the metering flap pivots make sure the area coverd by the large black cover is well sealed with silastic when you close up. The last time I did this servicing was last week end and it was only the second time in eleven years so it does work.

This work will not stop throttle valve switch full power selection causing rich vapour from the exhaust at low speed. This repairs low to mid range vapour trail from the exhaust.

I hope you can follow the direction when you do it once it is easy.

Good Luck

Steve

:classic:

[Daniel]

I suggest you mark the location you start from .I would move mine on a 280zx I had to stop hesitation.The problem was when I got my yearly state emissions.If I didn't return it to factory I would fail terribly.I just put a paint dot on the gear on mine.