Thanks LScowboyLS, will try it again tonite

 

I'm from Australia and have a Aus delivered 1994 LS400.

I purchased the caps from the list on the first page, but upon opening my ECU, so are compatible, some seem not.

ECU is part # 89661-50180, under that it has 175000-5234 12V

i should have needed
1993-94 LS400 needs 8 caps as follows:

Qty. 2 of 10μF - 50v
Qty. 2 of 15μF - 35v
Qty. 1 of 47μF - 63v
Qty. 2 of 100μF - 10v
Qty. 1 of 220μF - 16v

______________________

Upon cracking my ECU open, what i really need it

Qty. 3 of 100uF -50v
Qty.1 of 10uF- 50v
Qty.1 of 220uF - 35v
Qty.2 of 15uF - 50v

I ordered enough to do mine except for the 11uF caps i got were 35v- thinking heaps of headroom over the 10v needed, but i actually have 50v caps in there....

Any ideas if the 50v were maybe previously fixed/replaced and the 35v will be fine in place?

Thanks in advance

 

Higher voltage capacitors are mostly OK if they are not too high and can be mounted properly.

For an example to use a 50V capacitor instead of a 25V is OK but I don't recommend to use a 63V capacitor instead of a 10V. Too high causes the internal chemical activity low and poor. In other words, the capacitor goes into a kind of sleep mode when enough voltage is not applied for many days.

I have been dealing with electrolytic capacitors for many years and I often had unusual capacitor problems.

For examples, those capacitors stored in the warehouse for several months did not work well when used showing higher ESR and lower capacitance. But to keep using them for several days, they began to work better but not well enough. They needed some more days to be normal. They were in the sleeping mode and woke up after the enough voltage was applied for hours. Roughly speaking the voltage should be higher than 1/5 of the voltage printed on the original capacitor. The ratio 1/5 is based on my actual experience for low ESR capacitors used for lower voltage applications.

Below is nothing to do with a car but this is also an unusual characteristic of electrolytic capacitor. I discharged the capacitor short circuiting both + and - leads. Right after that, it was checked by a voltage meter and it showed 0V. The next day, I measured it again and it showed almost the same voltage I once have applied and short circuiting both + and - leads made a spark with a big bang sound. Fully discharged capacitors still hold some big energy somewhere inside, I understand. Since then I made it a rule to mount a capacitor after shorting both leads for a second or more.

 

Some Toyota/Lexus Celsior/LS400 models for export to various parts of the world used ECU designs that were late for the changeover, so your car in Australia may use something like the 1992 (USA) model capacitors

please do not use capacitors that are not from the links that Yamae and I provided in post #1 of this thread, they will not be the rare low-ESR, high temperature, long life, high ripple rejection premium Japanese type required for this fix to work

not sure what you mean by 11uf capacitors, but the 10uf and 15uF I linked to are both 50v or higher

I am not sure what you mean by 11uF caps

 

Sorry for the confusion/typo in the 11uF.

All capacitors i ordered were from you links on the first page. I even ordered some extra's which were not applicable to my ECU incase friends needs to do theirs and have different year models cars.

So basically my issue is that i ordered 100uF 35v capacitors, and fitted to the ECU are 100uF 50v capacitors. Your list of parts suggests that any 100uF capacitors only need to be rated to 10v.

Will the 35v be ok to use inplace of the 50v?

 

No, 35v capacitors are never OK to use in place of 50v capacitors, never, ever!

I have some alternative 100uf capacitor choices listed in my links that are 50v or higher, but here is the thing, I have likely seen the insides of more Lexus/Toyota ECU's than anyone on the earth, and I can't remember ever seeing Nippon Denso use a 100uF - 50v cap - they seem to always use 100uF - 10v in their ECU's - could you please take a photo of the 100uF -50v caps so that we can verify that these are the original capacitors to the car?

also, if you could post all writing on these 50v caps here in the thread, it would be helpful to identification

 

I think i may have found a source of the problem..... Looks like the ECU has been reconditioned previously in 2010.

Here are the pics as requested- Thanks again for any help on this.

The 100uF -50v caps are in the following positions incase it helps with what should be there

C740
C108
C105




http://www.flickr.com/photos/28550396@N04/11462190004/

http://www.flickr.com/photos/28550396@N04/11462261526/

http://www.flickr.com/photos/28550396@N04/11462143325/

http://www.flickr.com/photos/28550396@N04/11462266086/

http://www.flickr.com/photos/28550396@N04/11462198564/

http://www.flickr.com/photos/28550396@N04/11462151355/

 

unfortunately, the mentally-challenged person who rebuilt this failed on both counts, wrong type of capacitors and wrong size capacitors

I will post a map of the correct capacitor values in a few minutes, but this is a normal 93-94 ECU and should only have two 100uF caps!

 

correct map of your 93-94 ECU

 

Thanks so much for your help, it is sincerely appreciated. After checking the ECU, the rest look right except for the top 100uF which should be a 47uF, and i can only assume they are generic caps not the specific type required.

So i'm right to put the 100uF 35v caps in those 2 spots?

Car drives ok, but seems down on power and has a hesitation- so should be nice to see it smooth out with a power increase

 

definitely replace all 8 caps on this ECU with the ones ordered from the links - and yes, the 35V caps work great as a replacement for the original 100uF 10v caps

and please double check the polarity of all 8 caps after installation - they should all be facing the same direction

also thoroughly inspect for metal clippings and/or solder flecks when you are done

 

This is now all done. I took it for a quick drive, and it seemed to have a little bit more midrange power- still can't break traction on acceleration .

The miss has been reduced, but not eliminated- i'll look into the condition of the plugs/leads/caps/rotors and water temp sensor/O2 sensors to see if i can't get it perfect.

Thanks again for your help

 

try a genuine Toyota engine coolant temp sensor p/n 89422-20010 next
(the green one in the pic at the bottom of this post)

after that I would do plugs/wires/caps/rotors

plugs and wires - Denso or NGK (both are OEM) only - old wires are a common source of misfire - cheap sources are rockauto and amazon

caps and rotors need to come from the dealership (cheaper from online dealership such as Sewell Lexus, Park Place Lexus, Lexus Parts Now, Lexus of South Atlanta, etc.)

 

Awesome thread guys, I am also in Australia and have a 93 ls400, I have just ordered the list that is at at the start of the thread this morn and will have them fitted to the ecu as soon as they arrive.

The current problems I have are that sometimes the car just wont start, it will turn over but it is as if there is no fuel getting to it. I have put a jump lead from the b+ to fp terminal in the underbonnet diagnostic plug to ensure the fuel pump is getting power, after doing this it started fine so the mrs went up the street in it to do some shopping and it ran fine for 4 start stops then when parked at the supermarket it would not start again. left it there for 5 hours then it started fine again to drive home. This is not good in 43 degree c heat a few days before xmas..... other symptoms it has is the tacho and speedo sometimes decide not to work, the fuel gauge does not work yet the fuel light does. The lcd display for the climate control does not display either except for on really hot days. also the memory for the seat and belt settings does not work at all ?

I have swapped over to owning a lexus after driving a v8 statesman for years and so far it has not really been an enjoyable experience, I am hoping that this fix will be the solution......

 

this problem is not related to ECU caps - it is caused by high heat during the cars life, it seems