Originally Posted by Yamae

Toyota has started to use Nichicon's electrolytic capacitors that containing “quaternary ammonium salt / compounds" in the late 80s and has kept using them for a bit more than a decade. The reason why they used those capacitors was simply because the internal impedance was low enough and showed good performance in removing noise and ripples at DC lines.

A little before that many electronics industries in Japan started to use similar capacitors that were for non automobile use and faced serious leaking problems in the early 90s. The details are written below but all in Japanese.
http://ednjapan.com/edn/articles/1208/01/news006.html

I don't have the time nor the ability to translate all the contents so I will just translate the title.
“80年代末期の“亡霊”に注意” or “Watch out for the “phantom” in the late 80s”
The “phantom” here means the electrolytic capacitor which contains infamous “quaternaty ammonium salt / compounds". Judging from the title, it is dangerous to use this type of capacitor without taking any special precautionary countermeasures.

Most of the electronics companies in Japan stopped using this type of capacitor in the early 90s or mid 90s for fear of leaking problems. But many automobile industries kept using them　because they need good performance. Another reason was that they have been used in high reliability type-capacitors. Nichicon has been manufacturing special versions of this type for the automobile industries using specially coated lead wires with special sealing rubbers. One of my colleagues evaluated them and found the automobile type much better than those types designed for home appliances applications but the lifespan was not as long as those electrolytic capacitors that use regular liquids. Also the high reliability types were very expensive. I cannot show you the details of the evaluation results but what I can say is that the lifespan is longer than roughly 10 years or so but you cannot expect a lot if used for longer than that.

As I fix different ECUs as a volunteer, I came across many failed Nichicon's PF(M) type capacitors these days, some 12 years old, some 15 years old. What I can say now is that my colleague has done a good job evaluating the capacitors using an oven in the accelerated mode. In accordance with that and from my own actual experience, ECUs older than 12 years are ready to fail someday soon or later, that I can say with confidence.

Below is a failed capacitor used in a 97 Celsior. You can see how the leg has corroded and the part on the board where liquid has leaked out.



Those who want to replace Nichicon's type PF(M) capacitors to avoid future problems, be sure to use low ESR type capacitors. Never select capacitors just seeing the voltage and the capacitance. I recommend you to use Rubycon's type ZLH or Nippon Chemicon's type KZH. These do not contain infamous "quaternaty ammonium compounds" but their ESR is low enough. You also have to pay good attentions against electric static discharge when doing the replacing job. A wrist strap is definitely needed to use. Without it you might damage the ECU.

Originally Posted by djbrown01

and after driving it last night about sixty miles and running pretty much ok other than the occasional hiccup, I went to start it this morning and it wouldn't even stay running and if it did the rpms were very low and it was missing badly, throttle position sensor could cause this?

Originally Posted by LScowboyLS

the most high percentage technique of accurately diagnosing car issues, is something called pattern failure, which a company called Identifix has made a fortune with, and is what every decent shop and dealership uses now. It's basically the fact that your exact year and model will fail in the same places that everyone else's 95 LS400 has failed, it makes sense, as they were built in the same plant, with the same parts, by the same robots.