93 ls400 jerks
09-19-11, 07:17 PM
#16
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OK here's an update. I removed and disassembled the ecu. I expected to see a burnt spot on the printed circuit board or a capacitor leaking fluid. none found so I am now guessing that LEXTEK1 has a different way to check the caps. So if you please oh wise and kind sir, will you enlighten me?
09-19-11, 07:38 PM
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What you are looking for is a brown color under the caps. It will look like it was done with heat during the manufacturing process. As you can see the circuit board is coated in a green protective coating. The board should be green everywhere. Not discolored at all. Make sure the two halves are out of the case and don't worry too much about the ribbon cable. It is fairly robust.
Your symptoms sound very much like bad caps. I am sorry if I have led you on a goose chase....
Replace the caps anyway. If they have not failed, they will soon!
Take a Q-Tip and some rubbing alcohol to the board directly under the caps. If you see any brown color to the tip, they are leaking. Clean all that stuff off and make sure the board is clean under the injector drivers. They are black chips with three legs sticking up off the board.
Post a picture of the component side of the boards if you can. I can tell you more by looking at a pic of the boards.
Your symptoms sound very much like bad caps. I am sorry if I have led you on a goose chase....
Replace the caps anyway. If they have not failed, they will soon!
Take a Q-Tip and some rubbing alcohol to the board directly under the caps. If you see any brown color to the tip, they are leaking. Clean all that stuff off and make sure the board is clean under the injector drivers. They are black chips with three legs sticking up off the board.
Post a picture of the component side of the boards if you can. I can tell you more by looking at a pic of the boards.
Last edited by LEXTEK1; 09-19-11 at 08:13 PM.
09-19-11, 08:41 PM
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last 10 characters. hope this helps us, and I no longer fix cars for a living, so this is actually fun again. So don't worry about wasting my time.
09-19-11, 08:46 PM
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Brown Goo on pic's 4 and 8, see the discoloration going to those drivers??? Q-Tip that spot on pic 8. 220mf cap leaking its *** off!!!!
You have to clean that stuff off of the board under those drivers. That stuff is caustic and conductive!
Replace that 220 and the little one in front of it. Look for any more spots that appear like that brown spot on the board. Do you see the 3 traces that are covered by the goo? When you clean that spot with alcohol, it will take the green coating off too. But the green will only come off on those spots where the acid has eaten the coating. Its possible you will need to make some jumpers if it has damaged the trace.
Those 4 chips covered in goo are the injector drivers. The 220 cap is the TPS circuit and the little one is the ECT circuit I think... Perhaps it the NE circuit though... Your gas mileage may improve. You should reach about 21-24 MPG.
I hope I have enlightened you!
You have to clean that stuff off of the board under those drivers. That stuff is caustic and conductive!
Replace that 220 and the little one in front of it. Look for any more spots that appear like that brown spot on the board. Do you see the 3 traces that are covered by the goo? When you clean that spot with alcohol, it will take the green coating off too. But the green will only come off on those spots where the acid has eaten the coating. Its possible you will need to make some jumpers if it has damaged the trace.
Those 4 chips covered in goo are the injector drivers. The 220 cap is the TPS circuit and the little one is the ECT circuit I think... Perhaps it the NE circuit though... Your gas mileage may improve. You should reach about 21-24 MPG.
I hope I have enlightened you!
Last edited by LEXTEK1; 09-19-11 at 09:09 PM.
09-19-11, 09:22 PM
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ok, that took a lot of looking but I finally see what your talking about. i have cleaned the area thoroughly and corrosives have not yet done uncleanable damage. now, the drivers and the caps are radio shack items?
09-19-11, 10:54 PM
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just got my 4runner replacement today. 1993 LS400 90k miles. 
dealer says they will fix the skip in the engine blaming it on plugwires. but im thinkin its hte caps from this thread here.
runs awsome after the seafoam treatment. but still has that hesitation at 45-50mph about 2200 rpm i think it iswhen just cruising???? at 45mph its jerking slightly. at 50 its feels like it going to rip a motor mount out. but slower or hit the gas and its smooth as silk???
dealer says they will fix the skip in the engine blaming it on plugwires. but im thinkin its hte caps from this thread here.runs awsome after the seafoam treatment. but still has that hesitation at 45-50mph about 2200 rpm i think it iswhen just cruising???? at 45mph its jerking slightly. at 50 its feels like it going to rip a motor mount out. but slower or hit the gas and its smooth as silk???
09-20-11, 04:45 AM
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No need to replace the drivers. That goo tends to short them by physically surrounding the legs and the goo is conductive. But, your symptoms dont include that yet!
09-20-11, 04:52 AM
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just got my 4runner replacement today. 1993 LS400 90k miles. dealer says they will fix the skip in the engine blaming it on plugwires. but im thinkin its hte caps from this thread here.
runs awsome after the seafoam treatment. but still has that hesitation at 45-50mph about 2200 rpm i think it iswhen just cruising???? at 45mph its jerking slightly. at 50 its feels like it going to rip a motor mount out. but slower or hit the gas and its smooth as silk???
dealer says they will fix the skip in the engine blaming it on plugwires. but im thinkin its hte caps from this thread here.runs awsome after the seafoam treatment. but still has that hesitation at 45-50mph about 2200 rpm i think it iswhen just cruising???? at 45mph its jerking slightly. at 50 its feels like it going to rip a motor mount out. but slower or hit the gas and its smooth as silk???
09-20-11, 08:25 AM
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well its not a Lexus dealer. LOL but ya they said drop it off friday and all will be good. said they needed the whole day with it. thanks for the input. I am actually glad you are saying its not the ECU.
09-20-11, 11:27 AM
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Thank You Obie- Don- Kenobi
Road test, verified jerking on accel. Electronic engine control diag, found code 13. Check and verify integrity of cam sensor and crank sensor circuits. remove ecm, disassemble and inspect. found leaking capacitors in TP and ECT circuits. replace capacitors, reassemble and reinstall ecm. road test, found slight hesitation on accel from stop. adjust tp sensor and road test. engine operating normally and might I add... better than it has ever been. I feel extraordinarily enlightened. and if I get to the houston area any time soon, I'll look you up and we can enjoy a celebratory adult beverage. I hope this story helps some folks out there. I wish I had seen it quite some time ago.LEXTEK1, You rock!
09-20-11, 01:07 PM
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Well that's great! I am glad I was able to help you. You have completed your own ECU reman. Judging by the way you say it is running, the ECT cap was certainly bad and now you will see a nice bump in mileage. By the way it's really not ECT but rather THW (Thermal Water). Just everyone understands ECT without explaining. Your ECU thought it was -30 degrees and injected more fuel as a result. Your injector millisecond on times are cut by about 30 percent.
Enjoy and thanks for the nice comments....
P.S. Now take your instrument cluster apart and do the same thing. Those usually don't leak but the caps will look pregnant......
Enjoy and thanks for the nice comments....
P.S. Now take your instrument cluster apart and do the same thing. Those usually don't leak but the caps will look pregnant......
Last edited by LEXTEK1; 09-20-11 at 01:38 PM.
09-20-11, 05:03 PM
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Actually, i have a buyer coming tomorrow to look at the LS. I found a 2002 GS Sportdesign for my lady to drive. She likes it better because its smaller. And its also a great car. Sure hate giving up the LS though. its been a great car. And the mechanical issues have been fun. I have learned a lot about the differences between Lexus and Ford and they are not so far apart in a lot of ways. Except durability. I don't think Ford can match Lexus on that. now that you have seen her from the inside, take a look at the outside.