I know this thread was started more than two years ago, but since there are still tons of RX300/ES300 out there, this information is still very relevant and useful. I just want to say a big thank-you to GSSS and Geoff1 for posting such detailed and useful information. They took their time to explain what they did to help their fellow Lexus enthusiast/DIYer's. Hopefully everyone will be so willing to share as they do.
So here is my experience. I have a 99 ES300 with about 103K miles. About 1 month ago, I started having difficulty starting the car when it was cold. The car would start, ran at about 250rpm, then died. After that initial start, the car would not start unless I tapped the gas pedal while starting. Once the car started, I had to bring it up to fast idle, then it would idle by itself fine. No trouble starting when the engine was warm. No trouble with idling while the engine was running. After doing some searches, I came upon this forum, and I have to say this is probably the most detailed and accurate information out there. I initially thought about taking the whole throttle body off, then I decided to just use the short cut. After I took the coil pack off, I could definitely feel some resistance while turning the pintle shaft. I sprayed some cleaner into the small hole in the throttle body and around the pintle shaft. Just a couple of sprays and the shaft felt like it was gliding on a ball bearing (actually it is.) I sprayed a couple more time just be sure. Re-assemble everything, and the car started right up. I am going to observe for a couple of month before I can declare this short cut a success. I suppose if this problem returns too quickly, then I am going to have to do a more thorough cleaning. Several observations:
1) I bought a manual impact driver from Sears as suggested, just in case. It turned out that I didn't need it. What I did was I put a phillip bit inside of a 1/4 socket, which is attached to a rachet handle. The trick is to place firm pressure over the screw heads while turning the handle. Care must be taken so the phillip bit does not fall out of the socket. The screws came off fairly easily.
2) I initially did not see the wavy washer on the pintle shaft since the washer is so small. Then I saw it and went to grab it, and that's when it jumped out of my hand. That's the last I saw of it, as I spent the next 30 minutes looking for it in the engine compartment and on the floor to no avail. So I just put everything back together without it. I don't know exactly what's going to happen long term. I also wonder if I'll be able to just buy this wavy washer if it is a critical part.
3) I put a small cup under the lower air inlet to collect the throttle body cleaner as it traveled through the inner passages. Maybe it wasn't necessary, but I am just kind of weird about it.
I will give an update after a couple of months of driving.
Now only if that tapping noise from the suspension over broken pavement will go away......