Hi LScowboyLS or Yamae,

This great information, and very helpful! I have one question that I need help with the parts listed:

Will the capacitors listed by you, by their manufacturer numbers, be the actual low ESR caps? In other words, if I place an order with Digi-Key or Mouser electronics using the specific part numbers,will they be able to send me non-low ESR caps instead of low ESR caps with the same part numbers??? Or do these part numbers specifically apply to the low ESR caps only? Also, are these low ESR caps only manufactured in Japan, I mean by Nichicon, Chemi-Con and Panasonic? I ordered a set and noted that some were manufactured in Malaysia, and China, as well as Japan, and am concerned about putting these other ones into my ECU. Or, how can I be sure that the parts I got are really low ESR?

Thanks in advance for the reply

 

the caps I have linked to, have each one been extensively researched by myself and/or yamae - they are all low-ESR and yet not so low of ESR that would cause oscillation, they are in a very narrow range and hand picked for ESR, ripple rejection, temperature and other factors!

All of the capacitors are Japanese, either made in Japan, or at a completely Japanese facility in another country (like a Camry made in Kentucky but at a very rigid quality pure Toyota plant)

we only use and recommend caps from the 4 high-line super premium Japanese firms - Rubycon, Chemi-con, Panasonic, and Nichicon

the part numbers/links I posted specifically will specify the correct ESR - just use the links provided and you will get the correct caps!

PS - Mouser does not carry yamae's favorite cap, Rubycon, big oversight in my book!

 

I must write some more. Not so low ESR capacitors seldom cause the oscillation but those cause poor noise rejection and poor ripple rejection.

The oscillation is usually caused by too low ESR capacitors such as "ceramic capacitors", "aluminum solid capacitors with conductive polymer" or "extremely low ESR electrolytic capacitors". These cause the phase rotation up to higher frequency and the combination of the error amplifier cause positive feed back and this results the oscillation.

Those DC regulators in the ECU designed in 80s and early 90s are not quite oscillation free because of the insufficient consideration against the oscillation. In those days, too low ESR capacitors with bigger capacitance were not fully available yet. So you can not blame those engineers who designed.

In order to revive your ECU, you'd better to use capacitors listed by LScowboyLS. As long as you use those capacitors, you can expect a good result of low noise and less ripples as well as the oscillation free. His selections were based on his experience + search with some of my calculations, experiments and suggestions. He also has checked the availabilities there in US too.

 

Yamae and LSCowboy, you two are amazing with your right ups.

I first just wanted to say that you so much for everything, I'm sure you have helped countless members. The amount of time, research, and technical experience you guys have is breathtaking, and just reading this forum I think I've learned more than most mechanics out here.

I have an 92 SC400, I know we both share the 1UZ, and wonder if maybe this may be my issue. I have thrown everything you can think of, and have read and read posts, forums, my SC400 repair guide, and am stuck. Long story short, I have replaced every component and done every bypass to solve my rough idle/running-like-crap issue. Changed EGR Valve, IACV, TPS, cleaned out both upper and lower intakes. New coil packs, plugs, wires, 02 sensors (all) and countless other things. I'm able to get codes, which makes me think my ECU is ok, but even more interesting is that certain codes I'm gettting are clearing out, and then returning. Like I replaced both knock sensors, code went away, for a while, then when I replaced the EGR valve when I got the code 71. That code went away, and the code 52 came back. Turned the car off, for a minute, then I got a code 22 (ECT), and 15 (Ignition). AC works fine, and I'm able to pull codes. Could this be the beginning stages of a failing ECU? Or am I just really having those problems. I've been down already for 4 months and some change. Just trying to see what I can do. Just trying to eliminate this...

 

well let's just put it this way, I have a friend who runs a Lexus/Toyota performance shop, and he sees a lot of ECU's with failing capacitors, and guess what model of car he sees with this issue more than any other?

yep, you guessed it - '92 SC400's

 

Sounds like your symptoms may be caused by the initial stage of failing capacitors. But what I worry about is the weak compression or the valve timing.

I don't know that a 92 SC400 has a DIAG connector as is shown
here but this method is a simple way to check capacitors healthfulness. At the initial stage, those capacitors don't leak and you cannot judge by your eyes. The best way to check is to use a capacitance meter with an impedance analyzing function. But this is not easy as well as you need to remove capacitors. The method above link is simple and easy.

The reason why I began to post at CL was that many people here were having problems with ECUs but they really didn't know the fact. I had been partly involved in designing automobile equipments and what I noticed was that my experience might help those people. I feel happy that many LS400 here are revived. I would feel happier if SC400s were also revived.

 

SC400's are a bit harder to rebuild, you have screws on the back board filled with solder whose bonds must be carefully broken because on this model a couple of the capacitors are underneath the aluminum body of the ECU case frame and are inaccessible with the board mounted, unlike LS400

 

the 92 SC400 model is extremely common for this issue, and even if it is not the current problem, the repair should be done anyway, as a proactive measure, because all models (including yours) with these defective PF (M) series capacitors will have this corrosive leakage, and there is a very short time window between no leakage and corrosive effects so bad that the ECU is ruined and cannot be rebuilt, typically only a 4 - 6 month window to catch the problem once it begins.

 

LScowboyLS & Yamae,

You guys are awesome - both, for your knowledge and for your willingness to share it!! Thank you very much for this information and for your responses!

May the force be with you!

 

Hey LSCowboy and Yamae, thanks for your advice. I will pull my ECU today when I get some time. And I'm pretty sure it's not the compression btw. I did a compression test last month and everything was fine. Plus when I'm in neutral or in park, I rev up the motor and it sounds great. It's just when I'm actually in drive that I have this issue. And sometimes it is responsive especially when I get past 50.

 

Just curious if I could hire one of you two gentlemen to do it by the way. How much would you charge me for something like that? Thanks again guys.

 

They matched perfectly!!

My ecu and temp sensor:
This is weird because this car is 90 and it has the lastest model of ecu...



For my luck, the ecu was very clean inside, no leaking caps but it was failing a little at idle and running at second gear arround 2500 rpm:









I removed all of them and for my surprice none are nichicon brand! Why!?



I installed all from digikey and idle and second gear problem solved! Money used: $25 for caps and temp sensor, i had all solderings tools already

Thank you LScowboyLS and Yamae!!

 

good job!

PS - the capacitors in your car are the originals, and they are not the PF (M) series with the defect, your caps pre-date those!

this is a good example of how capacitors just go bad from old age!

 

I don't charge at all but I am only fixing ECUs and others for shops nearby just for my curiosity. I would be hired by you or someone if I were a guy who's life is not stable. Thanks for the company which gave me some big money for my patents.

 

Your patents gave them a lot more money than they will ever give you!