My AFPR is mildly cranked (at idle, the gauge reads 46-47 psi), and out of the blue I've started throwing 44's after extended (like hour+) driving. This is recent, I've driven for long periods before without this happening.

Are these possibly related, or is it just a messed O2 sensor like seems to be usual?

-Reno
89 Formula

 

Pressure seems high (assuming a stock setup, or even mild setup) which could make you run a bit rich and foul the O2 sensor...could be why it's reading a lean condition..not sure.

I'd toss a new on in and check the mv and see what the new sensor reads.

 

I HOPE that 46-47 psi is with the Vacuum Line off the AFPR. If not, you are WAY TOO HIGH.

However, Code 44 is a Lean Condition. This may be caused by: 1) weak fuel pump (high fuel pressure kills fuel pumps fast), 2) weak O2 sensor (I would have expected a Code 45), and 3) your injectors are "locking" from excessively high fuel pressure.

One hint, the LAST THING a basically stock TPI car needs is high fuel pressure. The eproms on these cars are already OVERLY RICH. The last thing these engines need is MORE FUEL!

Too many people have "bought" the TPIS sales pitch of "higher fuel pressure". Higher fuel pressure is a good thing WHEN the eprom has been modified to shorten the injector pulse widths. But if the eprom has not been modified, then you just made your car slower @ WOT due to too much fuel.

FYI, I ended up reducing my fuel tables by almost 20% to get my engine to perform optimally (right mixture). After over 5,000 miles of driving on my new plugs, my plugs are a light golden tan color now that I have adjusted my eprom. Plus, I recently got just over 29 US MPGs on a long drive from Kamloops to Calgary (almost 390 miles and I only used 13.07 US Gallons). I could have easily driven another 75 miles before I would have ran out of gas.

As for the "optimum fuel pressure", with a properly set up eprom, I like between 46-48 psi with the Vacuum Line disconnected. This gives a good spray pattern but is not too high to seriously shorten the life of the fuel pump.

Also, increasing fuel pressue has minimal effect on low load situations and their greatest effect on high load situations. It is not "linear" in its effect.