1993 LS400 engine stumbles or hesitation
#61
Check your AC
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.
#63
Moderator
#64
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.
#65
#66
Capacitors
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.
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.
#67
Lexus Champion
Everything I have stated here is rock solid accurate info.
and what makes them mil is their heat range of 115
The acid dialectric leaked out and corroded the board, but it has NOT damaged the board
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
Last edited by LScowboyLS; 11-04-12 at 02:30 PM.
#70
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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 ?
#71
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.
#72
Lexus Champion
the correct caps are listed in post #1 under currently recommended capacitors in my failing ECU capacitors thread
#73
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my solution...
Has anyone else ever found a definite solution to this as all of the threads that were started kinda faded out. I mean what is the point of having a forum such as this and many others if the thread starters never update their thread and give us some sort of idea what fixed theirs. Just my .02 cents.
#74
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lexus ls 400 1993 owner
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.