kcHotRodLs

that was a question I asked on the phone before hand. he explained that he would otherwise spend all of his time doing warranty work on capacitors that, even if they tested good at the time of initial service, would likely fail during the warranty period, causing customer angst and rework for the shop. when I got a phone update on my work, he said there was slight corrosion damage from one cap leaking. so yes, he neutralized that area and replaced all of the caps.

~kc

Unclebob9

Did mine today, When I started the car, 2 of them blew. So, I read ALL the directions and replaced the 2 and this time let them pre-charge, (as the directions say to) and all seems well.
You hear a nice loud "Snap" when they go, so it's easy to tell.
The other thing I may have done is to not leave much space between the capacitor and the board. My old ones were not leaking, but 2 of them were stuck to other parts (melted plastic).
My main problem was jerking. my traction light has also been on for years, it is not on now. Since the jerking is intermittent, It will take awhile to see if it is solved.
The car also had no power, I bypasses the fuel pump relay and got most of the power back, I will now re-connect it and see is that had something to do with the ECU.

Yamae

Thanks for the report, Unclebob9.
The power of the engine should be improved buy I worry about the your another problem. Bypassing the fuel pump relay simply means that the fuel pump is weak / fuel filter is clogged. The jerking of the problem is mostly caused by the insufficient fuel supply, as far as I have experienced. You can confirm it checking the fuel pressure.

dicer

So what do you mean precharge? I have never heard such a thing. More like the polarity was wrong???

Unclebob9

In the directions it says to turn the ignition ON and let is sit for a couple of minutes before starting the car. I did not do this the first time, I just started it. One blew immediately and the second about 5 minutes later.
However I did not realize that there was a positive and negative terminal on the capacitors.
So, you are very possibly correct. When I replaced the 2 that blew, I matched the direction to one that had not blown.
So, if this was the case, I lucked out getting 7 of the 9 in the right direction in the first place. (or they will also go out).
Since I have a spare ECU, I think I will go ahead and replace the Capacitors in it now and pay more attention to the old ones positions and swap it with the one I just put in the car.
It does appear however that the jerking has stopped and the Traction light has not come back on. (after a 45 mile drive). I am going to re-connect the bypassed fuel pump resistor relay and see how she runs now. We head s
South for the winter, so the car will be sitting for the next 6 months, so the next computer swap will have to wait until spring.

dicer

Electrolytic capacitors do have a certain polarity, it is marked on them, if they are not installed correctly they will blow. As far as letting it set before starting, that should be necessary everytime the battery is disconnected then. I still don't understand the logic of that. I'm surprised connecting the caps wrong didn't wreck the ecu.
The most important thing to do when working on these is to have a wrist strap, the one I have I plug into the wall receptacle ground, that will make sure there is no static charge on me.

Yamae

Are you sure about this?
The most important thing is not have any voltage difference between the human body and the ECU. You need to connect the wire to the ground line of the ECU board.

dicer

Sorry I also have a wire to the device as well to that ground point. Your right.

Yamae

That's perfect, dicer. Sorry I didn't know that you connected yourself to both.

fourstars

Im having problems with 2 of my ECU’s and I know it’s the ECU’s fault. I don’t have a LS400 but I do have a 92 SC400. 1 ECU with TRAC and 1 without TRAC. First ECU is throwing a code 52 (knock sensor). And no matter what I do, I continue to get that same code. I even switch the wires to the other knock sensor and continue to get code 52. Once the engine is off, the computer resets to NO check engine light … after driving for a few miles (5-10 miles) or up to 3k RPM, the check engine light re-appears causing the timing to retard. It also drinks a lot of gas. Second ECU, has a check engine light that will flicker and or dims out slowly. It will not allow me to check for codes. It runs perfect with NO actual problems affecting the engine. My question, is it possible these parts are the same for the 92 SC400 ECU’s? They are dirt cheap so I don’t mind buying 6 of each.

t2d2

iTrader: (8)

Yes, the instructions in this thread pertain to the SC400. If you go back a few pages, you'll find my posts from early August detailing which capacitors fit my '94. That'll be pretty close if not identical to your needed parts list, but you'll still want to double check before ordering so you don't miss any. I got two of everything and ended up needing one of them because there was an additional capacitor I didn't see hiding under the metal brace.

On the first ECU, I would say it's all but certain that it is the cause of the knock sensor trips. Mine did that sporadically and it turned out the lower capacitor had corroded the input terminals below it ... corresponding to the knock sensors and O2 sensors. Zero such problems in the three months since. Also, the fact that your second ECU doesn't throw knock sensor codes rules out anything else.

I don't know what the issue is on the second ECU.

mjkwee

Hi Yamae-San,

I am back because my intermittent problem is back. In your reply to me on 7/26 post #910 you suspected my problem maybe in my fuel pump area. My car failed recently after driving over 90-100 miles on a hot day and my '92 LS400 stalled in the middle of the road. I've already swapped my ECU in July so I am now looking at the Fuel pump system. My problem is intermittent and only when I drive long distance on a hot day.

Question that you may help me understand.

1. What is the purpose of the Fuel Pump resistor, P/N 28380A? I read somewhere another member replaced his FP resistor with good side effect to his radio audio it started to work and sound better, post #11 https://www.clublexus.com/forums/mai...em-solved.html
BTW, my radio audio has not been working for a while now. So I want to replace this part first because I want the good side effect with the radio audio working and per chance it may fix my intermittent problem due to hot condition.

2. Would you have the right version of the schematic of the Fuel Pump Relay/resistor for a '92 LS400? I've seen several versions posted in various threads. My mechanic and a second opinion could not read any diagnostic code from my swapped ECU right after my problem occured.

3. I replaced my original ECU (89661- 50032) with another ECU (89661-50042 w/ traction) from eBay in July after replacing the electrolytic capacitor. Is this the reason they cannot find a diagnostic code and does this have to do with the ECU requiring to be flashed with my car VIN? What problem will I possibly encounter with this ECU w/ traction? I now have replaced the electrolytic capacitors on my original ECU too. Should I swap back the original ECU?

4. I decided to replace the FP relay because I have over 185,000 miles. Part is on order.

I am disabled and It is not easy to get another replacement car because of special equipment. Another reason is I like driving my LS400. So I want to make the last attempt to fix my intermittent problem without spending a ton of money, and I want to be able to drive the distance without dying.

If the FP relay and FP resistor does not fix my problem, I am willing to replace the FP, a costlier undertaking.

BTW, I am having a tough time sourcing the FP resistor part for my 1992 LS400. Do you have any suggestions like a part number from Nippon Denso?

Yamae-San, thank you in advance for any help you can give and direct me.

Best regards,
Michael

P.S. Any help and answers I can get from the kind members is also welcome. Thank you too.

Yamae

The purpose of the Fuel Pump resistor is to reduce the current to the fuel pump. This reduces the power of the pump and the amount of gasoline to be pumped out but it is still OK for the constant speed running up to the highway speed. The fuel pump relay works only when the extra gasoline is needed such as the running up a hill, a quick acceleration, a start up and etc.

Regarding Q2, I don't have any.
I have no experience with Q3. I'd rather use the original ECU after replacing to recomended capacitors.

Regarding Q4, I would check the fuel pressure first before replacing the relay.

mjkwee

Thank you Yamae-San.

Mac2

Replaced the caps in the ECU of my 92 SC300 over a year and 15,000 miles ago. Have taken it through 100 degree heat and 10 below cold, and the car ran like new..........until 2 or 3 weeks ago.

Problems similar to before, rough idle and strange instrument panel readings returned. Got to checking and strangely enough found that the alternator was literally filled with oil!!! Bad valve cover gasket was the culprit------- new alternator and gaskets fixed things and am back enjoying the open road.