I have a 1992 ls400 the car stall intermittently. Once it stalls it will not start, then it starts. This has progressively gotten worse (more often longer time not starting) when it is not starting there is no spark. When I do the engine code check if it is not starting I get nothing. No flashing, nothing, check engine light does not even turn on (this is when shorting the terminals) when the car runs the engine code check just flashes like it should when there are no trouble codes. I read threads for over 2 hours and found nothing like this but I did find that if your engine code check does not flash it's the ecu. Just wanted some input, is this the ecu for certain? When the car is running it runs perfect.

 

Does sound like the ecu.

 

Well, I disconnected the efi fuse and noticed it seemed the plating on the fuse terminals were a little corroded, so I cleaned the terminal block with contact cleaner and put a new fuse in. So far the car is working perfect, just not sure if it's working as it should because of the new fuse or because of resetting computer.

 

mark my words - the problem is your ECU capacitors

this is a known design defect in all Lexus models from the 1990's

if you can solder and are meticulous, it's not that hard and about a $15 repair

my thread above gives complete instructions

 

LS cowboy, why did it suddenly work correctly?

 

probably the fact that you reset the ECU by removing the fuse, if you are really lucky, it will work OK for a while, but my money is that the problem will return this fall sometime, when it does, you know what you need to do!

 

LS cowboy I just read your entire post of the link you sent. It sounds like I should not wait since the caps leaking damage the trace. One question that was never answered on the thread was were to get the correct capacitors. Can you tell me where to buy the correct ones? I think I am going to change all of them asap. I remember this same issue on the miata airgbag module and if you waited too long it was not fixable due to the acid damage. I suspect that the heat in el paso where I live is accelerating the failure since I bought the car in Portland and there it is not very hot. I bet there is a pattern in that hotter areas have failures sooner.

 

It is not strange to have a capacitors leakage problem on your LS400 since she is 20 years old. 20 years is the time for young girls to be beautiful and attractive but for the capacitors that contain infamous “quaternaty ammonium salt / compounds", the situations are on the contrary. They are almost dead or already zombies. Zombies often damage the board as well as malfunction and damage the ECU. Before your ECU board becomes like your Miata's airbag module, you'd better to change the capacitors as soon as possible.

In Japan, those capacitors are called ghosts as I posted at #8 at the LScowboyLS's thread "all my ". I have been suggesting people how those capacitors were risky but many were not fully understanding me except LScowboyLS and some other gentlemen here.

 

Yamae why not replace them with a ceramic capacitor? This way they should last forever.
http://www.avx.com/docs/Catalogs/tap.pdf
http://www.ttiinc.com/page/search_re...s=-89597915_22

 

this actually does sound like it could possibly be the ecu. ecu issues are determined after everything else is eliminated or..its taken out and either looked at, or someone with the right equipment and know how can test it.
yamae you said "but many were not fully understanding me except LScowboyLS and some other gentlemen here"
well, i have a huge problem with that statement as you and cowboy have almost insisted on many threads that the caps were the cause of several cars here..one of which was having excessive internal engine pressure,turns out i had gotten involved in that thread and knew from reading it wasnt the ecu. so..from reading ur posts about caps in our ecu's i know full well the extent of ur knowledge concerning electronics...but, lets not lose sight of the fact that although they are 20 year old cars..its not the cause of all the problems you are saying..btw what does a 20 year old girl have to do with anything?

 

Ok python Biden

I think his point is that you should change all your capacitors even if your car is working perfectly as a preventative maintenance. I am going to order another ecu from eBay so I have a back up in case I screw up the soldering

 

rotflmfao...yea..change ur tranny fluid,do a tune up and replace ecu caps..thats the recommended 90,000 mile service.
good luck with the ebay purchase.
btw..check ur intial post topic and explain that
"No code reader no start read codes starts"

 

Ceramic capacitors have many merits but you have to be very careful for the oscillation due to the rotation of the phase caused by the extremely low ESR and a high Q. You can find this at http://www.ti.com/lit/ml/slup233/slup233.pdf

It says, "An output capacitor with a very low ESR value can cause oscillations for a different reason."
When Toyota's ECUs were designed for LS400 and others there were not ceramic capacitors of big capacitance and using them now might cause an oscillation and the ECU will be a mess.

This is why I don't suggest to use them. You need to compensate the phase and also you should limit the gain of the error amplifier very precisely. Without these, you should not use ceramic capacitors.

 

So what esr value is acceptable?

 

I did explain it. When there is no connection to the ecu car will not start. From what I read is that if you do not get a flashing check engine light when you short the terminals to check for cel codes then there is no comunication to the ecu.

From Wikipedia

Aluminum, and to a lesser extent tantalum, electrolytics have worse noise, leakage, drift with temperature and aging, dielectric absorption, and inductance than other types of capacitor. Additionally, low temperature is a problem for most aluminum capacitors: for most types, capacitance falls off rapidly below room temperature while dissipation factor can be ten times higher at −25 °C than at 25 °C. Most limitations can be traced to the electrolyte. At high temperature, the water can be lost to evaporation, and the capacitor (especially the small sizes) may leak outright. At low temperatures, the conductance of the salts declines, raising the ESR, and the increase in the electrolyte's surface tension can cause reduced contact with the dielectric. The conductance of electrolytes generally has a very high temperature coefficient, +2%/°C is typical, depending on size. The electrolyte, particularly if degraded, is implicated in various reliability issues as well.
High-quality aluminum electrolytics (computer-grade) have better performance and life than consumer-grade parts. High temperatures and ripple currents shorten life. Typical basic electrolytics are rated to work at temperatures up to 85 °C, and are rated for a worst-case life of about 2000 hours[17] (a year is about 9000 hours); commonly available higher-temperature units are available for temperatures of 105 °C, and a working temperature of 175 °C is possible. One of the effects of aging is an increase in ESR; some circuits can malfunction due to a capacitor with correct capacitance but elevated ESR, although a capacitance meter will not find any fault (an ESR meter will). Runaway failure is possible if increased ESR increases heat dissipation and temperature.
Since the electrolytes evaporate, design life is most often rated in hours at a set temperature, for example, 2000 hours at 105 °C, which is the highest commonly used working temperature, although parts working up to 175 °C are available.[18] Standard inexpensive consumer-grade electrolytic capacitors are rated for 85 °C maximum working temperature. Life in the operational environment is dictated by the Law of Arrhenius, which dictates that the capacitor life is a function of temperature and DC voltage. As a rule of thumb, the life doubles for each 10 °C lower operating temperature.[19][17] In our example, it reaches 15 years at 45 °C (for caps rated at 105 °C). The operating temperature however is not just the ambient temperature. Ripple currents can increase it significantly. The actual operating temperature is a complex function of ambient temperature, air speed, ripple current frequency and amplitude,[19] and also affected by material thermal resistance and the surface area of the can case.[17] In general, high amplitude ripple currents shorten the life expectancy, whereas low frequency ripple is more detrimental than high frequency. The EIA IS-749 is a standard for testing electrolytic capacitor life.[19]


So 5000hours at an average of 30mph would be 150k miles.