Fuel pressure sounds good to me. The last question on fuel delivery is the injectors. If they're plugged, they can't deliver fuel efficiently. So they just get held open longer to (try) get enough fuel to run right. This could get you an elevated long term fuel trim. Is the fuel economy terrible? Fuel in the oil? Plugs wet or dry? Does the exhaust stink like raw fuel or very rich?

You did mention a possible exhaust leak earlier in this thread. Do you know where that is at (upstream or downstream of the sensors)? Sure seems unlikely to me there'd be two simultaneous leaks upstream of both sensors but I have to ask.

That third oxygen sensor, bank 1 sensor 2, is just the catalyst checker. It has no bearing on how the engine runs. It's job is to ensure the catalyst is still cleaning up the exhaust, and trigger a CEL if not. The important sensors are the Bank 1 Sensor 1 and Bank 2 Sensor 1 (sometimes called upstream sensors).

Have you cleared those codes (after the maintenance you performed) and verified they return? This seems like a dumb question, since both LTFT and STFT are positive, clearly something is still amiss. Figured I ask anyway though.

What is the intake manifold vacuum at idle, and what is the idle RPM?

Anyone else have an idea? I haven't dealt with this particular problem myself, so just trying to offer ideas of what I think could be occurring.

 

Check Fuse 'E', 15 Amp, O2 sensor heater.

 

+1, they don't last forever...

 

Plugs are dry, don't smell fuel in the oil, exhaust doesn't stink. No idea where the exhaust leak is yet, I just know I hear it while driving. Not sure what the vacuum pressure is at idle, other than I feel it with a line disconnected. Idle is fine 1000 rpm at first start when cold then down to 750-800 when warmed up. About 700 idle in gear. Idles smooth. I clear the codes every time before driving it to determine when it triggers. No idea the actual fuel economy. Haven't been able to accurately measure. Trying to get the issues fixed before I make it my daily driver.

 

How are you clearing codes ?

 

My ELM has a function to read and or clear codes. Most times the 171 and 174 are pending codes but if I get on it going down the highway, it will set the CEL.

 

O2 heater fuse good, vacuum reads 17 steady at start up and after warmed up, drops when throttle opened and returns quickly. Spraying water over entire upper portion of engine to look for leak doesn't change vacuum reading. Not sure what else to look at. Not wanting to just change an intake gasket or o2 sensors without something definitive.

 

Anything else I should tackle if I am taking the upper intake off? I may just go ahead and replace lower intake gasket and clean fuel injectors while I'm at it.

 

What are pulling the upper for? Did you find a vacuum leak? 17" vacuum is pretty healthy. I would put a pair of oxygen sensors in it before digging into the intake. But yes if you're going to do it, clean the injectors, and if you're that far, a fresh lower intake gasket would alleviate any doubt about it's sealing. I had good luck with Berryman's in a can for injectors, with a 9V battery to cycle the injector open while applying pressure to them.