LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

96 LS 400 idle going up and down

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Old 02-18-11, 07:58 PM
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twofanman
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Links to test procedure for a ISCV for a 1990 are here. Probably very similar to your 96.
Old 02-18-11, 09:33 PM
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dvourthis
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Same ones I used, worked awesome!
Old 02-19-11, 09:32 AM
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yuyo
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ok thanks will check today.......
Old 02-19-11, 03:22 PM
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vdeleon
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Originally Posted by dvourthis
The way to test that ICV is to run positive jumpers to the two middle pins then ground the others. Mine was cleaner than that and it failed. Mine also ran just like yours. Just my recent experience. Rockauto.com had the part and it idles great now. If your MAF sensor is going bad I doubt it would run at all. I talked to a Lexus mechanic at the dealer and he said the ICV is a fairly common problem with this motor.
Had the same problem about fluctuating idle and sprayed the MAF w/ break cleaner, and the problem went away for a week, then I replaced it with a new MAF and solved it. Your car will still run w/ bad MAF but will stall every so often.
Old 02-19-11, 03:56 PM
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dvourthis
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Originally Posted by vdeleon
Had the same problem about fluctuating idle and sprayed the MAF w/ break cleaner, and the problem went away for a week, then I replaced it with a new MAF and solved it. Your car will still run w/ bad MAF but will stall every so often.
Do you know of a way to test the MAF and/or have PDFs from the FSM?
Old 02-19-11, 04:27 PM
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vdeleon
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Originally Posted by dvourthis
Do you know of a way to test the MAF and/or have PDFs from the FSM?
no books, just had a mechanic took one look and pointed to the MAF.
Old 02-19-11, 05:29 PM
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yuyo
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got my brake cleaner ready now waiting for this rain to stop i pray that works.......
Old 02-20-11, 10:21 AM
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yuyo
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so i did everything that was updated cleaned MAF and started the car after 30 seconds there comes the wild idle and a lot of smoke from the engine. i don't know what to do any suggestion i want to take the car to a shop but car is not registered and would hate to get it taken registration is 510 so i would really like to have the car running good before i put that money into the registration......
Old 02-20-11, 11:28 AM
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yuyo
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ok so i turn the engine on and then turned off ran to the engine and i can hear something like a vacuum leak but cant find it for nothing is there some kind of diagram that shows all the vacuum lines???????
Old 02-20-11, 11:59 AM
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dvourthis
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Spray carb cleaner on the tubes going to the engine, if you hear it rev you've found your leak. I would be careful spraying brake parts cleaner on your MAF filament. It's easy to damage it and brake cleaner is some hardcore stuff. Have you tested the ICV yet?
Old 02-20-11, 12:48 PM
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yuyo
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i used carb cleaner off the MAF i couldn't find the brake cleaner. no i have not tested the ICV. yet waiting for rain to let up.
Old 02-28-11, 08:21 PM
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yuyo
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so the problem is finally fixed after going to the pick and pull and replacing the ICV.... thanks every one for your help.... saved me thousands of dollars
Old 03-01-11, 05:34 PM
  #28  
dvourthis
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good, glad we could help
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