late2party

I forgot to mention one more thing. The fuel economy remains great even with the CEL light on. With or without the CEL, it's getting about 27mpg in the winter, and about 29mpg in the summer.

Hi Lexis: Thank you for your detailed reply. I guess I forgot to mention some basic info about the car. It has 163K miles, which is about 90% highway for the last 80K miles. I believe the engine is the 1MZ-FE3, which is different from 97-98 and has more in common with 00-01. The sensors and the cats were never replaced. The CEL would come on and off about a year ago, but now it just stays on all the time. I bought the OBD-USB cable and installed a software in order to figure out exactly what made the computer throw the code. The software is called OBD 2007, found at www.glmsoftware.com. It's actually not a free software, but it does provide a free 7-day trial period. I would hate to replace the O2 sensor if it is functioning properly, especially because B1S1 is sandwiched between the engine and the firewall and is kind of hard to get to. The graphs were obtained while the engine was idling between 750-2500rpm. I'll take it out on the road in the next day or two to see if it does anything different. Looking at the graphs, I would think that the B1S2 shouldn't be oscillating like that if it is downstream of the cat. I'll also try to erase the code first just to see at which point the light would come on again (I am sure it will come on again). Once again, thank you for your valuable input.

Hi: I had a CEL with P0420 (bank 1 cat below efficiency) on for the last few months. I tried to do some research here but couldn't find any definitive answer. Most say it's either the cat or the O2 sensor. I finally got around to do some diagnostic with the OBD-USB tool and got the following waveform: It appears that Bank1 Sensor2 is oscillating too much. One may conclude that the cat is bad. My questions are: 1) Is it true that the car (99 ES) has 3 catalytic converters (1 for each bank of V6, and both feed into a bigger cat) and 3 sensors (one before bank1 cat, one before bank2 cat, and one after the main cat)? 2) If the main cat is bad, why is only the code P0420 on instead of both P0420 and P0430 being on? 3) Is there a way to tell if it's the cats for either bank that's bad? I truly appreciate the input or insight that you may have.

Even though it has only been a little more than a week since I cleaned the IAC, but I could tell a definite improvement. As for the wave spring washer that I dropped but couldn't find, it didn't seem to make any difference, as far as I could tell. Funny thing is, in addition to solving the cold start problem, the car also shifts a lot better. The car used to "lurch" when shifting from 1st to 2nd, and now the shift is so smooth that I don't even notice it unless I look at the tach. I am wondering if anyone else has a similar experience?

I don't think the '97 ES300 has any spark plug wires, as each spark plug has its own coil on the top. Are you sure you had all 6 coils replaced before? That would be kind of drastic, not to mention expensive. What kind of spark plugs were installed last time? If they were platinum instead of irridium, then it's possible that they only last about 60k miles.

I just want to see if anyone has a similiar experience. I cleaned the IAC passage with some throttle body cleaner yesterday after having experienced hard cold start issues. The car otherwise would idle perfectly fine, it just didn't want to start when it was cold. So after I sprayed some cleaner through the small hole in the throttle body to free up the IAC shaft (by just removing the coil, without removing either the IAC itself or the throttle body), the cold start issue was solved. As an unexpected benefit, the shift quality actually improved. The car used to lurch a little during the 1st to 2nd upshift, as well as a fairly abrupt 2nd to 1st downshift. It has been like this for quite a while, way before the hard starting problem surfaced. This was most apparent during stop and go traffic, when the car constantly shifted between 1st and 2nd. After having driven the car today over 150 miles, I was surpised to find the much smoother upshift, so much so that it's actually imperceptible unless you look at the tach. You could feel the downshift just a little bit, but it's more "firm" than "abrupt" for sure. I wonder if anyone has an explanation for this. BTW, the car has 104k miles.

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......