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The condensed story is...the car is running rich: gas odors, bad gas mileage, consistently fouling plugs. The FI is all new from Nissan. I've had a Nissan certified mechanic check the obvious: fuel pressure regulator, FI connectors and the air flow meter. The fuel pres. reg. and FI connectors are all new and OK. His remark about the AFM was "its open all the way", which I interpret to mean that it's getting all the air it can get with the current AFM. His suspicion, so far, is that the AFM may need to be replaced. I would be willing to replace it, if it corrects the problem. My questions...does the AFM actually "go out"? Does anyone in this forum have a similar experience? Does Motorsport Auto sell a respectable AFM replacement? Any other ideas/suggestions...thanks.
 

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That does not sound like an Airflow Meter problem to me, if it is open all the way I would think it would run lean. How is the O2 Sensor? Does it run better when cold or warm? How is the COIL? Are ALL the cylinders running equily rich? Does your IDLE STICK? ( a much more common AFM problem in my experiences ).
????

Scott Milella
 

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Sounds similar to my problem, but mine develops as the engine warms up. I ponied up $200 for a reman. AFM and it did not solve my problem of running rich. It did take care of another problem I was having with the car coughing under acceleration at low RPM, so I kept the unit.

I'll keep my eyes open to see if you solve your problem. I will problably try the coil like Scott suggested, but my car doesn't have an O2 sensor, so I know that's not the problem.

Good Luck
 

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If I remember correctly the single sensor in charge of the mixture is the head temp sensor, located near the oil filter, that would also not be a bad place to look.

Scott Milella
 

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O2 Sensor

Are you sure you do not have an O2 sensor? I have never heard of a Fuel Injected car ( especialy a Z ) not having a O2 Sensor?!? Oh and I need to revise my last reply, I believe the O2, sensor, and the head temp sensor work together to adjust the mixture.

Scott Milella
 

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RE: O2 Sensor

The 75 doesn't have a O2 sensor!.
I would clean the connections on the head temp sensor
first which is located on the thermostat housing.
r/r if needed.
 

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RE: O2 Sensor

Not until '82 I believe on the O2 sensor, everything pre doesn't have one. Remember that your 75 was in the leaded gas days, O2 sensors and leaded gas do not get along.

Ken
 

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RE: O2 Sensor

No O2 sensor on the early L-Jetronic systems. Many things can effect rich:lean. Water temperature sensor can cause the car to run rich. Worn out AFM spring. Maladjusted Throttle position sensor. Mechanical timing out of whack as in chain stretch or rebuild with head and deck cut without corrosponding adjustment to the cam gear. Low fuel pressure can cause fuel to "dribble" into the cylinders in a manner that is not condusive to combustion so it leaves the cylinders as raw fuel or HC as the smog tech would call it. Most times it is as simple as dirty connections since the signal sent is a resistance and dirty connections increase resistance.
 
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