Oldtreemech

Any luck on your problems? How did the fuel pressure and pump checkout? I had a whole series of problems just like this check my post if you like. Make sure you have fuel pressure and ignition. Replace the plugs and clean the throttle plates. Check the electrical resistance values of the IAC motor. Next consider cleaning the IAC valve by a complete disassembly and clean electrical section with CRC electrical cleaner and the probe area with throttle/choke cleaner. Slightly lubricate the motor gear positioning srew threads with Mobil One oil. Before reassembly try spining the motor from one limit to the other positioning limit on its shaft to make sure it spins very freely and the shaft slides freely thru the housing! Next assemble the probe to be almost completely closed position but back it open about a turn or two on the motor. Reassemble and see what happens. I'm going to poar some pictures soon so check it out. Good Luck!

I had similar problems after removing and cleaning the IACV several times. What appeared to work was a combination of adding a full can of Seafoam to the gas tank with additional fresh premium fuel and cleaning the IACV shaft and adding a Mobil One oil film to it to make it work smoothly. Clean the threaded stepper motor part of the shaft as well and add a film of Anti-seize or Mobil-One oil film. After cleaning and lubricating the shaft the spring on the shaft should freely spin the stepper motor and move the shaft to the forward or closed position. It solved a lot of my problems but occasionally have some misfires and hunting idle speeds but believe thats mostly bad fuel/water and needing a fuel filter change. Use some CRC Electrical Motor cleaner for the shaft and the stepper motor windings and Moving magnet on the shaft. Once I put it back together it worked great. :)

Hey do a google search for sc400 window regulator and there are several sources for the part around $150. Well that's the part then theirs the labor to install it. Do it yourself or pay for install probably a 2-4 hr job at what ever labor rate so maybe somewhere between $350-550 [ LEXUS dealer upto $750]. Some of the forums have procedures to checkout if you want to do it yourself. Good Luck!

UPDATE: Cranked it up today and immediately caught and ran smoothly at correct cold rpm setting of around 1600. Ran for 1-2 minutes and rpm began to decline to around 1000 so I was beginning to think that Sea Foam had cleaned everything out and I was finished...........wrong! It stumbled/misfired a couple of times and the Trac and CEL lights came on and the rpm climbed to 1600 rpm. Restarted a couple of times same CEL and Trac lights. let it set a couple of hours and started right again No lights , ran 1-2 minutes and stumbled again but not as bad then the lights came on. Drove around about 5-10 minutes to try and mixup the gas and Sea Foam to clear it out some more. Still trying to get the fuel filter off without damaging the fuel lines etc. Maybe change out temperature sensor next since it seems to show up as it lowers rpm in warmup. UPDATE: Cross my fingers maybe the adventure if over. Cranked up immediately this morning and no CEL or Trac lights and ran smoothly. Held the rpms up to 2-3K and let it warm up. Had one little period of reducing rpm and one stumble but very minor. After warmup was at correct rpm and ran excellentl. Cranked it up a couple of more times and ran it around the block several times an a couple of full throttle drills to finish mixing and purging bad gas or water in the tank. Added more fuel and will press on for now. Will add more Sea Foam for SURE. :) UPDATE: Okay it ran well enough to get to the emission test and passed. Then on way home back to high idle then a little later surging and hunting idlle speed and finally back to choking and missfiring but never went to backup mode. So back to more Sea Foam and changing fuel filter and maybe another IACV rebuild. <_< Quick Note: Before I left to go to emission test check the O2 sensors which read about .250V which normally would be really lean compared to other Manufacturers which normally would say around .5V. I did pass but now it looks like I'm getting close on the Catalytic converters needing replacement because the NO was very near the limit! Followup: Cold night startup went well but back to idle speed surge hunt betweeen 1500-2000 rpm. Revved it up a little a couple of time s and let it warm up a little above 2500-3000 rpm. Still hunting rpm so shut it down and restarted and then its stable at 1600 and continued to warm up and settled down to 1000 at warm temperature. Oh one follow-up after the codes went away this morning did a double check on test codes before emission test trip. All Clear and quick 11111 all clear code. It didn't store any codes from earlier stumbling and misfires and was out of BACKUP/LIMP home mode. :D

UPDATE: Cranked it up today and immediately caught and ran smoothly at correct cold rpm setting of around 1600. Ran for 1-2 minutes and rpm began to decline to around 1000 so I was beginning to think that Sea Foam had cleaned everything out and I was finished...........wrong! It stumbled/misfired a couple of times and the Trac and CEL lights came on and the rpm climbed to 1600 rpm. Restarted a couple of times same CEL and Trac lights. let it set a couple of hours and started right again No lights , ran 1-2 minutes and stumbled again but not as bad then the lights came on. Drove around about 5-10 minutes to try and mixup the gas and Sea Foam to clear it out some more. Still trying to get the fuel filter off without damaging the fuel lines etc. Maybe change out temperature sensor next since it seems to show up as it lowers rpm in warmup. UPDATE: Cross my fingers maybe the adventure if over. Cranked up immediately this morning and no CEL or Trac lights and ran smoothly. Held the rpms up to 2-3K and let it warm up. Had one little period of reducing rpm and one stumble but very minor. After warmup was at correct rpm and ran excellentl. Cranked it up a couple of more times and ran it around the block several times an a couple of full throttle drills to finish mixing and purging bad gas or water in the tank. Added more fuel and will press on for now. Will add more Sea Foam for SURE. :) UPDATE: Okay it ran well enough to get to the emission test and passed. Then on way home back to high idle then a little later surging and hunting idlle speed and finally back to choking and missfiring but never went to backup mode. So back to more Sea Foam and changing fuel filter and maybe another IACV rebuild. <_< Quick Note: Before I left to go to emission test check the O2 sensors which read about .250V which normally would be really lean compared to other Manufacturers which normally would say around .5V. I did pass but now it looks like I'm getting close on the Catalytic converters needing replacement because the NO was very near the limit!

UPDATE: Cranked it up today and immediately caught and ran smoothly at correct cold rpm setting of around 1600. Ran for 1-2 minutes and rpm began to decline to around 1000 so I was beginning to think that Sea Foam had cleaned everything out and I was finished...........wrong! It stumbled/misfired a couple of times and the Trac and CEL lights came on and the rpm climbed to 1600 rpm. Restarted a couple of times same CEL and Trac lights. let it set a couple of hours and started right again No lights , ran 1-2 minutes and stumbled again but not as bad then the lights came on. Drove around about 5-10 minutes to try and mixup the gas and Sea Foam to clear it out some more. Still trying to get the fuel filter off without damaging the fuel lines etc. Maybe change out temperature sensor next since it seems to show up as it lowers rpm in warmup. UPDATE: Cross my fingers maybe the adventure if over. Cranked up immediately this morning and no CEL or Trac lights and ran smoothly. Held the rpms up to 2-3K and let it warm up. Had one little period of reducing rpm and one stumble but very minor. After warmup was at correct rpm and ran excellentl. Cranked it up a couple of more times and ran it around the block several times an a couple of full throttle drills to finish mixing and purging bad gas or water in the tank. Added more fuel and will press on for now. Will add more Sea Foam for SURE. :)

UPDATE: Cranked it up today and immediately caught and ran smoothly at correct cold rpm setting of around 1600. Ran for 1-2 minutes and rpm began to decline to around 1000 so I was beginning to think that Sea Foam had cleaned everything out and I was finished...........wrong! It stumbled/misfired a couple of times and the Trac and CEL lights came on and the rpm climbed to 1600 rpm. Restarted a couple of times same CEL and Trac lights. let it set a couple of hours and started right again No lights , ran 1-2 minutes and stumbled again but not as bad then the lights came on. Drove around about 5-10 minutes to try and mixup the gas and Sea Foam to clear it out some more. Still trying to get the fuel filter off without damaging the fuel lines etc. Maybe change out temperature sensor next since it seems to show up as it lowers rpm in warmup. UPDATE: Cross my fingers maybe the adventure if over. Cranked up immediately this morning and no CEL or Trac lights and ran smoothly. Held the rpms up to 2-3K and let it warm up. Had one little period of reducing rpm and one stumble but very minor. After warmup was at correct rpm and ran excellentl. Cranked it up a couple of more times and ran it around the block several times an a couple of full throttle drills to finish mixing and purging bad gas or water in the tank. Added more fuel and will press on for now. Will add more Sea Foam for SURE. :)

UPDATE: Cranked it up today and immediately caught and ran smoothly at correct cold rpm setting of around 1600. Ran for 1-2 minutes and rpm began to decline to around 1000 so I was beginning to think that Sea Foam had cleaned everything out and I was finished...........wrong! It stumbled/misfired a couple of times and the Trac and CEL lights came on and the rpm climbed to 1600 rpm. Restarted a couple of times same CEL and Trac lights. let it set a couple of hours and started right again No lights , ran 1-2 minutes and stumbled again but not as bad then the lights came on. Drove around about 5-10 minutes to try and mixup the gas and Sea Foam to clear it out some more. Still trying to get the fuel filter off without damaging the fuel lines etc. Maybe change out temperature sensor next since it seems to show up as it lowers rpm in warmup.

In the middle of chasing ISC (ICAV) valve repair and interaction with CEL and TRAC lights. I've read several post over the forums and chased down thru the following checkouts: Plugs, Plug wiring, Distributors caps/rotors, coil packs, igniters, temperature sensor, temperature switch, MAF, Throttle plates cleaned, VFV for EGR and Pressure Regulator. I've replaced the ICAV with an Ebay one, same problems just different idle speed. I've taken the ICAV apart and cleaned and oiled it slightly with Mobil 1 oil. Started up at 800 rpm and no CEL or Trac lights! I thought I was finished... wrong! It idles for say 3-5 minutes and then stumbles and misfires a couple of times and dies! Starts up again and then misfires and CEL and TRAC lights back on! Runs a while longer and dies again after more misfires and backfires. Spray some throttle cleaner in the intake and start it back up. It hits immediately and runs great and no CEL or TRAC lights runs for another 2-4 minutes at 800 rpm and revved up with no misfires etc. Dies again and I start it again and this time idle speed goes up to 1500 rpm and CEL and TRAC lights back on. Now I'm thinking its partly related to some bad fuel problems so I've added SeaFoam to tank with a few more gallons of fresh fuel and tried it again about 5-6 hours later. Cranked right up no lights again runs for 3-4 minutes and back to misfires and CEL and TRAC lights. Will change fuel filter tomorrow after PBwrench soaks over night. Earlier checked oxygen sensor voltages at temperature and showed rich condition ~ .975 V. When I'd rev the engine up to constant 2-3K voltage would lean some to say .900 or so. But if I revved it up and released the throttle the voltage would reflect ~.500v a good operating range at normal conditions. But then it quickly returns to the rich voltage level. Haven't killed the sensors or CATs yet but it won't be long if I don't get this corrected. I don't get any Check engine codes when shorting E1 and T1. This may be due to ECU moving to BACKUP/LIMP HOME mode. Not sure so I have a Ebay ECU on way to check this out. Any Other suggestions? :(

List your model, year , # of owners , price when bought and from where lenght of ownership and attributed problems and repair costs. Also mention where you had it fixed ( lexus, independent, midas or diy). When it was done. Any mods done to the car and its costs. If desired your age and insurance you pay. If you have any picutes in the gallery put links in the post so we can have an idea about the car. Please only post once and if you have a question either pm the member or make a new thread . This will keep the page from being filled with excess. SC400 1992 2 owners $9K in 2001 from a friend in Fairfax Va owned for 8 years and experienced the following problems[First owner had Alternator, Battery, Power steering Pump leak, Gauge set replaced , AC issues], I've had the following problems repeat Alternator , Battery loosing charge over 2-3 days, AC charge, AC control issues, Heater control valve, poor alignment from Lexus dealer corrected by NTB, Leaky sunroof and passenger upper door seal, Fuel Pump failure, clear coat paint issues, IACV issues driving me nuts now.