Jacklalane

I took my 01 RX300 with 286K miles to the dealership to have the codes read. It only came up with one P0171. The service mgr showed me on his computer that in his database from techs reporting to a subscription database that on that particular code, out of 194 cases reported 181 times it had been the MAF sensor needing replacement. Sounded like pretty good odds to me and a Denso MAF cleared the code. After driving a few miles my CEL came back on. This time when I pulled the codes it triggered multiple codes: P0174, P0300, P0306 and P0136. I haven't driven the vehicle for a couple of years, but less than 1K miles prior to parking it I replaced the knock sensors and wiring harness, plugs, ignition coils, MAF sensor, timing belt and water pump, the variable timing solenoids and bank 1 and 2 O2 sensors.
With the rig idling I did spray starting fluid around all the places where I could possibly be losing vacuum with no discernible change in RPMs. The vehicle is running fine, but I need to get to the bottom of this.
Does anyone have any thoughts on what system/component(s) would cause all these codes to trigger at once? Thank you for any help you can provide.

Jacklalane

I also replaced the IACV...Regarding the misfire codes: I can detect no misfire or misfire related performance issues even when accelerating hard...

Lexmus

Was the P0171 before or after the two year parking hiatus?

Other than that, did you put sufficient gas stabilizer into the tank prior to parking it?

Jacklalane

It was after the two year hiatus...And no, I didn't put any stabilizer in it...The reason I parked it was that I picked up a Camry Hybrid as a daily driver and though I didn't anticipating using the Lexus a lot, however I didn't think it was going to be sitting idle all the time. Now with summer coming (and me newly retired) I am wanting to spend time in the mountains, so I would really like to start using it again if I can get it fixed..
Your question did remind me though that I made a 600+ mi trip to WA and back to pick up a tow dolly last August. Thanks so much for jumping in.
BTW, I loved your tutorial on the downstream 02 sensor replacement and have one on the way. A starting point on the rest of it would be great.

ukrkoz

Mice chewed up on wiring somewhere? Happens quite often on cars that sit do nothing for long time. This will give you all kinds of trouble codes.

Jacklalane

Do you have any advice on a starting point in troubleshooting this? Thanks again...

Lexmus

Get a bluetooth OBDII reader and torque app for your android phone, reset the codes, and see which one comes back first.

Report short and long term fuel trims and MAF reading.

Were the parts you replaced all OEM or Denso?

Lexmus

When you report the fuel trims and MAF, do so at idle when warmed up and at around 2000 rpm.

Jacklalane

I'll get one and do what you said...We are going out of town for a few days...just wanted to say that so you don't think I'm ignoring your advice.