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1994 LS 400 problems -missing sputtering

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Old 06-17-14, 01:41 PM   #1
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Unhappy 1994 LS 400 problems -missing sputtering

First I apologize if this has been addressed previously or in another forum. I bought this 1994 Lexus LS 400 over a year ago and I love it or at least I did until about a month ago. About a month ago I started encountering problems with the car's operation. It began missing and sputtering and acting as though I had purchased some bad fuel and that still could be the problem, but I am starting to have my doubts. I live over 2 hours away from the nearest Lexus dealership so taking it into the dealership to check codes or diagnostics isn't a likely option. I have begun exploring the possibility of purchasing a diagnostic code scanner to check and see if it may be a sensor going bad. So far I have changed air and fuel filters, plugs, and changed brands of gasoline plus added a can of sea-foam fuel cleaner. It has stopped stalling however now it will take spells of running well then running like crap. When it runs well, it is the car I fell in love with, when it craps out, it won't even pull itself up a hill without manually shifting to low1. So I have a couple of questions for Lexus owners or DIY'ers out there.
1. Have you encountered similar problems and if so, what solutions did you find?
2. What diagnostic computers have you had experience with? or used? I have been looking at the Innova 3120 code scanner. Has anyone here used one and is it a simple tool or complicated to use or is it even useful? I am considering buying a scanner to fix the car cause I still love the car, but I can't just start replacing things or else I will simply send it on down the road to a new owner which I really don't want to do.
Please help if you can and I want you to know it's appreciated.
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Last edited by RA40; 06-17-14 at 04:46 PM.. Reason: descriptive title
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Old 06-17-14, 02:54 PM   #2
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is the check engine light on? if so retrieve the codes..u don't need a scanner
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Old 06-17-14, 03:12 PM   #3
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I also have the instrument cluster problem which is on my list of things to fix. But I don't know how to decipher the flashes to get the codes...or how to get to that...
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Old 06-18-14, 08:14 AM   #4
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You don't show what part of the country your in... hot climates make the ECU capacitors susceptible to failure... have you checked the leaking capacitor thread. The parts are cheap and it's a known weak spot, over time, for these vehicles. I'd replace them just to rule out the ECU, and you know you're going to need to anyways.
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Old 06-23-14, 02:40 PM   #5
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I appreciate the ideas. I live in Kentucky. When I tried to get the codes as described above, it didn't throw any codes. Also I found one mechanic in town with a SNap-on computer that plugged up under the dash and when he hooked up, all he got was failure to communicate.... So I'm leaning toward ECM/ECU..... I have found rebuild services listed on EBAY that sound reasonable.... My next question if this sounds like the direction I should go is.... JUST Where is the ECM/ECU located and how do I remove it?
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Old 06-23-14, 03:14 PM   #6
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Soundss like bad ecu. Mine failed to communicate and od off was randomly flashing although car drove perfectly. I tried replacing capacitors but I messed it up because the circuitboard was thick and I had a cheap soldering iron that did not get hot enough. Luckily I found good used one on CL for $50. No more issues now. It's under glove compartment do a search

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Old 06-23-14, 07:16 PM   #7
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It could be ECU caps but first try some simple things. You mention replacing plugs and filters but what about both distributor caps and rotors? Those are maintenance wear items that many fail to change(they can be a bit of a pain to get to) and yes, the rotors can give you all kinds of intermittent fits when they wear out.

It may not be the issue but if you are not sure about their condition or when last replaced, consider new caps/rotors before you go much farther with the troubleshooting. http://www.lexls.com/tutorials/ignit...tor_rotor.html
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Old 07-01-14, 07:46 AM   #8
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Default Anyone with a diagram of how to remove ECU?

Does anyone have a diagram of how to remove the ECU? I removed the kick panel, but have struggled with the glovebox removal. Apparently working on it while standing on my head isn't working well either...
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Old 07-01-14, 12:13 PM   #9
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Once you get the glove box out, the ECU is easy to remove.

The diagram in post #1 of the ECU thread has the necessary detail give take a few nuts depending on year.

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Old 07-01-14, 12:13 PM

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