kayuwong

When I did have blown/leak caps in my ECU, funny thing is that AC compressor won't engage. Turn on your AC and see if any cold air is coming out. Bad ECU will shut off AC compressor in order to avoid further load on the engine. If no AC, problem must be your ECU. If you have any friend who can swap you a good ECU and try, that will be a excellent test. Good luck.

kayuwong

Test and confirmed. Replaced two bad caps, old unit work just as new. Good luck guys.

Yamae

Congratulations on your success, kayuwong.
Are there any more Nichicon's PF(M) caps other than those two in your ECU?

kayuwong

Yes, there is around 7 or 8 more cap like that, but I only replaced a blown one and one more which has brown goo shown at the lead contact. A full overhaul will be replacing all caps. Oh well old saying is if not broken, don't touch it. LOL. Good luck.

shoob

https://www.clublexus.com/forums/ls4...ng-nuts-5.html

similar issue, but mine is load related.

freegard

Yes, capacitors do a sundry of different things depending on how they are wired into the circuit.
The capacitors you need have a certain name and every word of their name must be present or you do not have the correct type of capacitor. The capacitors that fail both in the instrument cluster and the ECU are the same TYPE: "POLORAIZED ELECTROLYTIC" You must clarify both polarized and electrolytic when buying them. The next most important feature is the grade of the capaitor which is its heast range. The highest grade is called "MIL spec."
for military grade; and what makes them mil is their heat range of 115. These caps are filled with a dialectric, think of it as a fluid. Poor grades leak as they get hot. That is what you see on your circuit board as most dialectrics are acidic. The acid dialectric leaked out and corroded the board, but it has NOT damaged the board, it merely is cosmetic 99% of thime. It jnust looks bad. Use Isopropyl alchohol and a lint free cloth to clean the board before you install your Mil grade caps.

Okay the next thing that must be identical is the microfarad value. uf is the symbol you see on the side of the cap which translates microfarad. That must be exactly the same. You take a 100 microfarad out you replace it with a 100 microfarad.

Voltage is the other number you see on the cap. You CAN use a higher voltage with absolutely no ill effect whatsoever. Let's say you have a 25V but you can only find a 50v 100uf. Install the 50v; it will hurt nothing. I am not going to get into electronics too much, just think of it as a capacitor that can stand 50v before it fails as opposed to 25v before it fails.

Thgese caps have a negative and a positive lead. YOU MUST!!!!! put them in exactly how they cam out insofar as which lead went where. See the black line down the side of the Cap? That is the Negative lead. Get that wrong and your problem will not have been fixed. The word POLARIZED is what denotes a negative and positive side. You CANNOT (and a lot of people do) walk in and ask for an electroytic capacitor. It will not be polarized and will look identical except for that black line down the side of it.
You cannot substitute a tantulum electrolytic. That won't work either. If you adhere to everything I wrote here you WILL get the correct capacitor. If you do not you wont. The only thing that can be a little different (but it must ALWAYS be higher and never lower) is the voltage.

My knowledge is based on empirical education and experience and working on electronics (avionics) on the S3A Viking Submarine Hunter Killer aircraft in the Navy, and a father who taught me electronics when I was a litttle kid. I do not give bad information. Everything I have stated here is rock solid accurate info.

LScowboyLS

no, some of the things you have stated are accurate, and some are misleading, some are inaccurate, and the most important consideration on capacitors was actually omitted

the correct heat range for Lexus ECU capacitors is 105C

in the case of our Lexus's the dielectric is a strong alkali (a base, the opposite of an acid) and what has leaked IS damaging to the copper circuit board traces, mine were almost ruined

and the most important characteristic of the correct replacement capacitors, even more than their values being correct is that they are LOW ESR type, which is a special type and not typical.

please let Yamae make the technical posts on ECU's and capacitors, as a Japanese ECU designer with dozens of patents, he dwarfs the combined knowledge of everyone else on Club Lexus as far as ECU capacitor considerations

PureDrifter

iTrader: (10)

please provide some background sources rather than just saying you have empirical evidence

python

iTrader: (4)

talk about high jacking a thread

gsmoot1

I have a 1991 lexus ls400 having the same and more problems including surging,power loss, tachometer ,gas needle not working properly or not working pulled the ecu no burnt capicitors or resistors board looks good could this be fuel pump or wiring harness ?

Twista4004

Are you able to actually test a couple of your capacitors? Sometimes they look good but are still bad. I'd get the thing rebuilt anyway. I have the number to a guy who does it for $149. I haven't sent mine yet but he's been around for a while I hear.

LScowboyLS

the correct caps are listed in post #1 under currently recommended capacitors in my failing ECU capacitors thread

MechTech24

i was given a pristine 91 ls400 by my friend because he explained the car would not " run right" and had basically all of the problems that I keep reading here... it sat for almost a year before he gave it to me... anyways the car did have all the problems posted here and more, same codes and everything... I replaced the voltage regulator within the alternator and the fan clutch...also the positive battery wire from the battery to the alternator was frayed and also replaced the TPS for good measure.. on the passenger side, under the hood, just behind the air filter housing, just above tire though... there are two ignition control ignitors which I believe are connected to the cams they sit one above the other ...I also switched those connectors one into the other and this car flies like a bat outta hell... just worked for me... did the same to my relatives 96 model ...same result... we are rollin... hope it helps

amarjit

i have a lexus ls 400 1993 mechanic has has put in new spark plugs and leads and a air filter new synthetic oil with lucus oil additive. the car is misfiring, has anyone have suggestions.

Gene01

Very likely the plug wires are crossed.