A 0.047 uF capacitor will pass less ripple than a 0.47 (assuming some relatively broad distribution of frequencies), so your ripple would actually be greater than you measured (for Yamae's comparison).

 

Hello All,

'93/LS400

Since the last time I posted all has been working fine (approx. a few months ago or about 3000 miles worth). This AM the Trac-Off light and Check-Engine lights go ON, car ran okay, it ran quiet.

I have a repaired ECU now used in the car(Caps to spec, 2 or 3 traces on the circuit board were clipped in a botched job). I have a 2nd spare repaired, untested ECU.

 

Question here: have two ECUs. Let's say one is "A" and one is "B". A will not surge my fuel pump therefore my car will not start. A is immaculate looking on the inside, no oil leaks on caps etc, but fails to run the car. So I recently replaced with B. B will start the car and run it, however ive got complete missfire on passenger side cylinders (2,4,6,8)(also read code for missfire on 6, with a history of this). Upon inspecting the insides of B, I founde two leaky caps, both right next to eachother (with capacitor board on the bottom, it's the two caps closest to the harness inputs.) They read: 100uf10v and 47uf63v.

Here's my question:
Can I take the leaky caps out of B, clean it up, and replace with the same two caps from A, which are nice and shiny?
Thanks in advance.
Edit: Also extreme smoking when B runs the car, very rich smell, and I kid you not.. About 3-5 mpgs.

 

Simply replace them all. Costs only $20 for 2 ECUs

Capacitors can't be checked by eyes. You need an impedance analyzer to check the ESR and the frequency characteristics.

 

Did you install those capacitors correctly? I mean the polarity is very important. Your type of problem happens when reversed.

 

So, at what point is the ECU board not fixable as to oily leakage. From my inspection, I have not found any breaks in the traces of the board, but there is a damned good amount of leakage that came off one capacitor. Does that not matter? As long as everything is intact? I've cleaned the affected area with water/baking soda, then vineger, then distilled, then alcohol. All of the loose gunk is gone but the oil that actually got into the board remains. Is that alright?

 

It's not alright. It is no use crying over spilt liquid and repentance comes late. The liquid is a strong alkali and conductive. The invaded liquid to the internal layer makes a current path and often this causes problems.

That's the reason why I suggest people to replace capacitors before the leak starts as a preventive measure. Many of those who have followed my advice are now reporting that the engine runs much better in addition to risk reductions.

 

Does anyone know how to disable the "Traction Control System". I could not find any relay/fuse in the main plastic covered box. When you turn on the car the "Traction Control" comes on by default, then there is the on/off switch on the dash. By disabling the "Traction system" this may close the "check engine" light.

 

Yamae - I installed all of the proper caps, all facing the same direction. I did one at a time and made sure they were facing the same way as the original ones. I'm going to get the correct .047uf cap for the ripple test and try again. The board looks great and all of the new caps "look" fine. I know that doesn't mean much.

 

I'm in the middle of tackling this project right now and thought I would add a little tip that made things easier for me.

Instead of trying to remove the old capacitors as a whole, I simply cut them off (as close to the base as possible) leaving a good portion of the prongs protruding. I then used needle nose pliers to hold the prongs while de-soldering on the opposite side of the board.
Not sure if this has been discussed before but it made things a little less frustrating.

I have not been able to start the car at all and also have a CEL. When I tried to hook up my scanner, it would say that I had no codes stored.....WTF????
Hopefully all goes well and my next reply will be accompanied by tears of joy.

By the way, my vehicle is a 96 and it looked like my 63v 47uf cap is the culprit. No visible leak, but looks a little bloated compared to the rest.
Hope this helps

 

I worry about the liquid coming out. Aged capacitors are sometimes quite empty though.

 

The correct capacitor is a film capacitor of 0.47uF. The capacitor 47uF you have used may not be a film capacitor and it's a kind of electrolytic one or an equivalent which needs long time to charge up as well as it has some leakage. You only should use a film capacitor when you measure the ripples.

 

Got the ecu out... PITA... Threw my back out doing it. I'll be replacing the caps sometime this week. So while I have it all dismantled is there something else in there to have fun with or do something to? Also I swapped out my air ride for springs but never could find the AS computer. Or the right wire to cut. Would it be near the ecu? My compressor still pumps air and it's quite loud and annoying. I was hoping the compressor would die but knowing Lexus it hasn't, it's been a year.

 

Hi,

I have a 98 ls400 & im thinking about changing the caps sometime this weekend. I was thinking about using the recommended caps, but I found some polymer caps with better specs (lower ESR & higher ripple current ratings). I wanted to know if there would be any advantage to using the polymer ones instead of the recommended ones from the first page.

Also, does anyone know what the case size for each of the original capacitors are?

thanks for your time.

 

Sorry to say, that's an amateur's idea, I must comment. I don't recommend you to use them. Without measuring the gain and the phase of the error amplifier, and also without knowing the margin to oscillate, it sure is dangerous to use them.

Many polymer capacitors cause oscillation problems. You will be getting to know reading the pages below.
http://www.mikrocontroller.net/attac...illosation.pdf
http://www.andretahim.com/Projeto/Li..._Stability.pdf

You also can find some more at the page 22 of this thread.


I don't have the data for the case size. Why don't you measure and post those here?
It also would be nice trying to use polymer capacitors and report us the resut and the phase margin.