Aaron: Google for "rx300 diagnostics pdf".
When multiple codes are present often there is a single problem which cascades out affecting multiple sensors. Clear the codes, and then wait for the first one. For example, one bad coil can lead to multiple misfire codes. I usually swap the coil from the second one reported to the first, and see if the order changes. When it does I know which one is bad.
When the CEL is turned on the car goes into 'limp' mode, and the engine will be rough. It seems to me the car goes rough a few seconds before the CEL illuminates.
Good luck
rob, your original description sounds like an abs problem.
It presents like an intermittent grinding sound from one or more wheels while braking. You will also feel it in the brake pedal.
The abs warning light does not always illuminate for this.
Today I was outside my 99 RX300 cleaning the windshield. Doors and windows closed, engine off, radio on. I heard an intermittent buzzing sound by the passenger door and thought of your question.
The radio speaker was inducing a buzz in two places - the passenger side mirror, and the door handle/door handle trim.
Try the radio to see if it helps localize your problem.
I would think this would be symptomatic of a failing wheel bearing, failing u-joint, broken abs tone ring, a loose brake component, or, if you are really lucky, something stuck in your tire tread.
My 1999 AWD has 193k miles. I was planning to do the timing belt soon, last one was done around 90K.
Is it expensive to replace the crankshaft seal and idler bearings?
Is this a recommended service? I don't recall it being mentioned previously.