Frankie_B Posted April 7, 2007 Share Posted April 7, 2007 Gents, I have a 98 ES300 with about 120k miles I took it for emissions test a few days back, and although it passed, i'm still worried. Here's what i got: IDLE: HC ppm: 126 Limit: 150 CO,%: 0.04 Limit: 0.7 RPM: 698 2500 RPM: HC ppm: 91 Limit: 150 CO,%: 0.62 Limit: 0.7 The test was performed on warmed-up engine. I've been reading that HC is unburned fuel. Additionally, I can say that i've changed my spark plugs recently (to OEM Platinum) and did the Seafoam treatment twice in the past 6 months. Oil (Mobil 1 Synt.) and Air filters are changed every 5-6k miles. As far as the engine performance goes, i notice a high fuel consumption (regardless of driving style, best i could get was 21 mpg on highway and 19 mpg city (that's with virtually never going over 2500 rpm!). I've tried resetting the ECU but that didn't do anything. I'm worried because it looks to me like something might be wrong with the ignition system. What do you think are the most probable causes? Should I look at wires first, or distributor/rotors? Any leads would be appreciated. Quote Link to comment Share on other sites More sharing options...
Toysrme Posted April 7, 2007 Share Posted April 7, 2007 Oxygen sensors are making you run rich. You can clean the MAF wire with a q-tip too, search for that. Fuel, not ignition. Quote Link to comment Share on other sites More sharing options...
lenore Posted April 7, 2007 Share Posted April 7, 2007 Oxygen sensors are making you run rich. You can clean the MAF wire with a q-tip too, search for that. Fuel, not ignition. Hey, toysrme, you seem to have a lot of experience with the oxygen sensors, tell me, I have a 99RX300 and have no indications and car runs fine, but I have 135k miles on it. Mileage is same as when I got car new, but the oxygen sensors have never been changed. From your experience is it time for me to change at least the two pre cat sensors? Quote Link to comment Share on other sites More sharing options...
Frankie_B Posted April 7, 2007 Author Share Posted April 7, 2007 Would you recommend changing all three? I suspect they've never been changed. Quote Link to comment Share on other sites More sharing options...
Toysrme Posted April 7, 2007 Share Posted April 7, 2007 You can just change the offending sensor, but around that mileag they normally become increasingly un-responcive & read increasingly richer. Which is why gas mileage starts going down. ;) I wouldn't change the post-cat sensor until you had a trouble code for it. Its only purpose in life is to tell the ECU the cat still works. It has no bearing on engine tuning. lenore - you can if you want too. If the mileage is the same the ones you ahve are probably still functioning descently. Quote Link to comment Share on other sites More sharing options...
Frankie_B Posted April 7, 2007 Author Share Posted April 7, 2007 OK, Local dealer wants $230 PER SENSOR. I'm gonna order them from Park Place Lexus They have 'Front' and 'Rear'..I take it 'Rear' is post-Cat and 'Front' are the ones at the engine, so I want to order 2 Front Sensors, is that right? *EDIT* I also found this: http://www.densoproducts.com Super Class OE identical O2 sensor 234-4622 FRONT; 2 Sensors Required for Vehicle; $89.20 So that's even cheaper than newlexusparts! Red flags go off, no? Quote Link to comment Share on other sites More sharing options...
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