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Discussion Starter · #1 ·
Hey everyone

I have been trying to track down a P0171 lean code for quite a while now. Today I adjusted the valves and checked fuel pressure. Adjusting the valves went fine, but when I tested fuel pressure, with regulator vacuum disconnected I was seeing 39 psi and with the regulator vacuum connected I was seeing 29 psi at idle and 37 psi under load. So, it seems that the regulator is operating correctly and lowering fuel pressure at idle and increasing pressure during load. And the low fuel pressure most likely means a restriction in the system. I have already changed the fuel filter, but maybe the aftermarket filter doesn't allow enough pressure through? It doesn't seem like fuel pumps go bad very often. So, I'm kind of out of ideas on what the issue could be.

(98 Integra RS)
 

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Discussion Starter · #3 ·
Wouldn't a restriction in the fuel regulator actually increase the fuel pressure? Also I don't think duty cycle is monitorable on this car. I kinda wanna just throw a fuel pump in it and see what happens.
 

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Discussion Starter · #5 ·
"P0171" means, "System Too Lean (Bank 1)". Most commonly due to a vacuum leak somewhere.

Additionally, you could also have an exhaust leak before the O2 sensor. If you have an exhaust leak, the O2 sensor could be reading too much oxygen in the fuel mixture, which will then in turn cause the ECU to dump a bunch of fuel into the engine to compensate.

Start searching for a vacuum leak, then check your exhaust.

Don't assume that's something is wrong with the fuel system. Sounds like the fuel system is ok at this point from your description above.
Hmm the intake manifold is missing a nut, meaning someone's been here before...
 
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