fuel pressure regulator

I believe it is located on the drivers side fuel rail just past the bend after the fuel line coupling
 
Fuel pressure on the LS is regulated by varying the power to the fuel pump, as it is a returnless system.
The PCM senses fuel pressure (relative to manifold vacuum) via the fuel pressure sensor installed between the fuel rail and the manifold. It uses the comms bus to send commands to the REM to alter its PWM to the fuel pump motor to give it more or less power as needed.
 
Hm. Because my STFT is right where it needs to be at all speeds, idle, cruising, accelerating.. but my LTFT is remaining +10 higher than my STFT no matter what. No matter how long I drive it the LTFT doesn't level back with the Short term.
 
So.. if I understand correctly I've maxed past the top short trim value 10 times over basically? And that is my now default-ish operating range to keep 14.7:1 because of whatever problem I have to hunt down?
 
So.. if I understand correctly I've maxed past the top short trim value 10 times over basically? And that is my now default-ish operating range to keep 14.7:1 because of whatever problem I have to hunt down?

I'm certainly not an expert at this, but to me it kind of implies that you may have a small air leak somewhere. A little extra air at cruise and idle might alter the long time trim, but not much alter the short term trim at high power conditions?
 
The more I read up on it.. a raised LTFT with proper STFT could just be a result of the higher airflow from the aftermarket intake and exhaust?
"The modifications we perform on our engines are mostly designed to increase airflow. With a greater airmass entering the engine than is accounted for by the MAF and/or VE table, the AFR becomes lean, as the fueling is set for a lesser airmass. To compensate, the STFT’s, and eventually the LTFT’s, swing positive to a greater or lesser extent, depending on the modifications. "
 
The more I read up on it.. a raised LTFT with proper STFT could just be a result of the higher airflow from the aftermarket intake and exhaust?
"The modifications we perform on our engines are mostly designed to increase airflow. With a greater airmass entering the engine than is accounted for by the MAF and/or VE table, the AFR becomes lean, as the fueling is set for a lesser airmass. To compensate, the STFT’s, and eventually the LTFT’s, swing positive to a greater or lesser extent, depending on the modifications. "

AFAIK, that could be true.
 

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