P0171 Nightmare

[sdfoxredo]

Hello to all of you Lexus owners, I am new, and have nowhere else to turn.

I bought my 1998 es300 recently and I do love it, except for the lean code nightmare. I have a p0171, bank 1 lean code, and I can not get it to go away. It does not run lean when it's cold, it only runs lean after it warms up, I notice from the quality of it running. If I drive it only a little and I never let it get warmed up all of the way, I don't get the code. Obviously we all drive more than that. 

I bought a smoke detector, found huge leaks in the throttle body gasket and IAC Valve, and fixed them. P0171 came back. Replaced many old vacuum lines, pcv valve, and it's still here. I also smoke tested the exhaust, there are no leaks. Here is everything I've replaced:

Bank 1 Oxygen Sensor (OEM)

MAF Sensor (OEM)

IAC Valve (aftermarket)

Brake booster (had a vacuum leak, aftermarket)

I checked fuel pressure, hooked up the Guage and started it up, 50 psi

 

I dont know what to do. What could it be? I heard possibly a leaking purge solenoid or something? I understand everything but the evap system. I have replaced all evap lines, could a bad solenoid in the evap/vacuum plenum cause a p0171? Smoke test reveals no leaks now, but I did notice when I did the exhaust smoke test that it seemed that a little smoke started coming out of the intake. I figure maybe the egr or something. The car runs great until Its warmed up and put under load just right, then it starts to misfire and run like *BLEEP*. The CEL is intermittent, but the p0171 is always stored.

 

What do I do next? Please help me.

 

[McBrian]

You're still getting unmetered air in somewhere. Keep replacing rubber hoses (especially from the intake to all of the vacuum solenoids) the accordions from the airbox to the TB, and maybe think about the intake plenum gasket(s)?

[sdfoxredo]

Just now, McBrian said:

You're still getting unmetered air in somewhere. Keep replacing rubber hoses (especially from the intake to all of the vacuum solenoids) the accordions from the airbox to the TB, and maybe think about the intake plenum gasket(s)?

Wouldn't those leaks show in a smoke test though? Will continue to replace all the vacuum lines I haven't yet

[McBrian]

Smoke tester is great for finding big holes with a small amount of pressure.

Engine is fed air with vacuum and it's gonna find the easiest place to leak it in if its there.