Yamae

Some version of ECUs had 9 electrolytic capacitors and also non-Nichicon capacitors were used. The company Marcon used to be one of the brother companies of Toshiba but now it was sold to Nippon Chemicon. Denso has used Marcon's capacitors but not too many. As far as I was informed, those capacitors had some minor problems at very cold district like Alaska.

Those capacitors seldom leak but the liquid inside evaporates little by little as aged and the capacitance decreases and the ESR increases. Those cause the poor ripple and noise rejection. Judging from the age of your 92, the evaporation must be not little. It would be better for you to replace those as a preventive measure. I am sure you will be noticing that the engine would run better than before after the replacement.

LScowboyLS

Yes, I can confirm that Marcon (Toshiba) capacitors were used originally on some Lexus models especially in the 90-92 year models (also in many Toyota models in the 1980's), and yes, I believe those are the two 15uF caps you have there

LScowboyLS

also, I think the 10th cap you will find hidden up under the frame of the ECU and quite hard to get to!

if it is not there, please recheck the top board where the Marcon's are for a 3rd cap

fsuguy

Hi,

I may have missed the last cap, but don't think so. Attached are pictures of the boards - 2 for the top that flips open, showing the 2 caps and nothing similar to them. The bottom board has nowhere the last one can hide except behind the ribbon cables, and I don't see them there.

Has anyone else with a '92 experienced this - having only the 9 caps? My LS does not have the trac, so do you think the last one is for that option??

TIA

LScowboyLS

apparently yours has only 9, I have seen this situation before, but it is less common than 10

PS - I can see 15uF marked on your Marcon caps in your pic!

YagerD

Is anyone on here selling refurbished ecu's or can fix other peoples? This is a great write up but with my work schedule I just do not have time to do it myself.

LScowboyLS

I have seen nothing but really bad work and incorrect capacitors used on all of the "rebuilds" on ebay and elsewhere, as well as the commercial places, they just don't seem to understand the unique rare type of capacitors required for one thing, not to mention some of the soldering skills.

I think the that world is just becoming short of those old school engineering types that put us on the Moon, etc. - these days robots and solderwave machines do all of the soldering and these yahoos that are basicaly mechanics, don't seem to understand that just because it is a 100uF capacitor, doesn't mean there isn't a myriad of different types, and they never seem to want to go to the expense and time of seeking out the rare hard to find expensive type of capacitor that is simultaneously low-ESR, high temperature, high ripple rejection, long life, premium Japanese, as found in my links in post #1

fsuguy

LScowboyLS,
Hi and thanks for confirming the caps. Fully agree with you about the decline in effort to fix things properly! You and Yamae, as well as several other folk on this forum are exceptions, and for that, happily, we are thankful!

All the best!

LScowboyLS

do you see now where it says 15uf on the Marcon caps? (right beside 35V)

did you change the caps yet, how is it running?

fsuguy

Yes... after I took the pictures I noticed the marking on the other side. I changed the caps and it was fairly straightforward. Had to fashion a makeshift puller out of a paper clip for caps that were in hard to reach spot, though. Can post a pic if anyone cares to see it.

Cannot say yet whether there is a definitive change - I was having intermittent CEL issues - off and on, and that is not happened yet in two days; also, high end running seems smoother and better acceleration - not sure if that is my imagination, but the engine definitely is quieter

None of the caps I replaced were Nichicon, nor are those in the replacement (standby/backup) ECU I got, so I think it possible that the defective caps were in the later gen 1 models and on (ECU #89661-50032). I will replace the caps in the backup ECU, just in case my soldering work was off (don't think it should be, though!)

Thanks to LScowboyLS and Yamae for the very detailed information, part numbers, etc. Would never have undertaken this repair without your help and write-ups.!!!

fsuguy

...by the way, LVC is one of my favorites from the westerns with Clint Eastwood in the spaghetti westerns!!

LScowboyLS

your car is over 20 years old, your caps were worn out regardless of brand!

and this is LVC, I just got too old to do the westerns any more, so now I rustle up ECU's!

simrx3

same same. big ups to the guys involved in sorting this issue and the effort gone to help us all..

ive noticed a massive improvement in mine with those capacitors you specified..

Carlamari

Hopefully I won't be kicked off here if I don't post on here! i do read the information for my car, members are very helpful:-)

RickyGee

Thanks cowboy and Yamae. I gave my sweetheart 94 LS400 to my student son nearly 7 years ago (Nuclear Engineering degree, Computer Science degree, now his Masters in computer science $$$$...) and he’s still driving it. It was still looking and driving like new until recently when it started stumbling hard during moderate acceleration and flashing a TPS code. A new TPS sensor didn’t change anything (??!!?!) and the symptoms and code remained. I was ready to take a trip to my son's house and thought I would be rebuilding the ignition system, when I ran across this discussion.
8 new capacitors later (your specs, thanks), the car is running like new again. I had previously replaced the caps in the cluster power supply, replaced the gauge needles and posted a fix for the sticking needles ( see https://www.clublexus.com/forums/ls4...ot-work-4.html ) and replaced the HVAC LCD, so I wasn’t hesitant to try this repair myself. But I must admit, it was challenging mostly due to the double sided printed circuit board (the solder didn’t want to melt on both sides at once…) and the tight spaces for my rather bulky solder iron. So your encouragement was very helpful and the writeup very much appreciated. I love this forum.
My old Lexy turned 20 this month, 170k miles and it now appears she is ready for another 20.

BTW, the 15uf capacitor and a 10uf capacitor had both leaked, causing minor damage to the PCB foils, and the 47uf was beginning to leak. False codes and missing codes, poor idle and no power. Now it's like it was when new, but still adjusting itself. Thanks again guys.