I am at loss. The most annoying P0125 won't go away even if I clear while driving. Occasional/pending P0171 (system too lean). MPG is between 5 and 12 for 10-mile average. Both A/F sensors (before catalytic conv-r) are new (checked them several times). Borrowed a remanufactured MAF sensor from Autozone. Solved nothing. I guess there is a vacuum leak somewhere, or misplaced vacuum lines after engine swap, but I cannot find it.

 

Ok, found one leak. Will search more.
Don't know how to fix this sucker. Home Depot have hoses like this?

 

Yeah Home Depot has those hoses. I just sometimes use some duct tape as a temporary fix and to test.

The P0171 is an accompanying error, the P0125 is the one to focus on. If a mechanic near you has an advanced OBDII scanner they could see the readings coming off the banks and that could help narrow down where the problem lies.

 

That cracked hose (it goes to hot part of lower manifold) was REALLY loose. I was able to take it out even without moving the clip. Let me replace it and see if it fixes anything.

 

Keep me informed as you find things, I will help you as best as I can.

What about those cracks on the manifold?

 

I replaced the manifold completely.
Going to Home Depot now...

 

Ok, fixed that hose. Now my RX has part of Kitchen Sink Spay Hose :-) P0125 still continuing coming back. Among with pending P0171, P1135, and P1155. I am absolutely sure that A/F Heaters are Ok. The resistance on them measures 1.0 Ohm. Maybe something with wires. I will check again from ECM harness. Can it be that third unheated O2 sensor behind catalytic parts?

 

That 3rd O2 sensor would pop off P0420.

 

Now it has pending P1130 and P1150. Is it possible that both of new sensors are defective?

 

Yes, but unlikely. Assuming you are using OEM Densos.

The two things that stick out to me are a leak/crack, even small one or something somwhere that is just not tight. 1130 is related to the one behind the engine and 1150 is on the front. Since it is both, to me this suggests something perhaps with the either the fuel delivery BEFORE reaching the engine and/or the air intake system, even though effects of combustion are what the engine is looking for.

I know your engine was overhauled, but even gas sitting in the tank for a bit and then having the vehicle restarted can cause some issues. I went on a trip to Jamaica for a week, came back and my RX started up like $@%#.

With the air intake, one of my pet peeves was always that the stock airbox was never truly tight and hot engine air was going to sneak in through gaps in the grooves (I used to wrap it in duct tape).

 

I am about to go to my track, but as I thought about this a little more, I am placing a little more emphasis on the volume of air you are getting into your engine as I noticed your MPG.

 

Lexus manuals specify Heater Coil Resistance to be 11 to 16 Ohms. My new Denso sensors had resistance of 1 Ohm. I bought them off Ebay for $100 each. They've been in unopened Toyota factory packaging. Does Denso provide any kind of direct warranty? Very strange. I am thinking to try those Bosch sensors from O'Reilly, they have them for $179.99 each.

 

Now I am really confused.

Section SF-72 (page 1162):



Section SS-9 (page 140):

 

I would stick to the Densos though. I don't have an ohmmeter handy (I should) so that I could check mine to see what is up.

The damn manuals are full of errors. A few weeks go Fern uncovered an error with ATF fluid levels between the owner's manual and service manual.

Unbelievable.

 

I just replaced the bad A/F sensor with a Denso one bought at rockauto.com for $160 shipped. CEL code was P1130 and P1135, with P0171 and P0172 accompanying the bad sensor. So far after I clear the code, it has not come back. Bosch made a mistake a while back (labeling a o2 sensor as a A/F sensor), it sources from Denso so why bothers getting Denso second handed.