nivek5sfe

hey guys, i was having problems with my sc300 that i found to be somewhat of a common problem for our cars. the symptoms were that it continiously had white smoke coming out of the exhaust, was not throwing any codes so the check engine light never came on, compression check was "ok" just a tad low, and the oil was completely diluted with gas. initially i couldnt find any information using the search on here or any other sites and as many others i thought it was a problem with the head gasket. so from there i broke the engine down to the head and literally the day before i got the head off i found a thread describing my exact issues and how it was the ecu great. so sure enough i opened up the ecu and found capacitors that had gone bad.

im primarily making this thread to document what to look for people having this problem or to use for future reference.

with the ecu open this is the area that i found the bad capicitors in, its in somewhat of a hard spot to see.


i got as close as i could with a flashlight and camera to get some pics. it turned out that both of the capicitors were corroded and looks like they had leaked. one was only hanging on by one connection instead of two and it looked like the second bare was hanging on by both.

skirts

iTrader: (1)

Are you going to be doing the repair yourself?

nivek5sfe

no im not repairing it. i have a spare ecu that is hopefully working

nivek5sfe

for future reference here are some threads describing the problem

https://www.clublexus.com/forums/per...you-think.html
https://www.clublexus.com/forums/per...ing-sc300.html
https://www.clublexus.com/forums/per...m-exhaust.html
https://www.clublexus.com/forums/per...ecu-issue.html

skirts

iTrader: (1)

Ive got a sc4 and the cel comes on and off while driving with a code 28 and im wondering if it could be a ecu problem...

sc-driver

iTrader: (7)

great thread! It's not hard to replace those if you know how to de-solder and solder.

those 2 middle links you posted don't work.

nivek5sfe

yeah i figured it wouldnt be too hard to fix. i just opened my spare ecu and i didnt see anything wrong visually so hopefully it works.

and thanks for letting me know about the links, they should be fixed now.

92es300man

hi guys --- I have the same issue -- white smoke coming from exhaust and major fuel loss with gas in the oil -- plus running horrible. I was informed by some that it was a blown head gasket and/or warped head. I alread had the back head off and after planing and a valve job, there is ticking from the back head and some smoke coming from the back of the engine -- ?? -- not sure about this --- maybe needed a thicker head gasket after the head plaing ??? -- any insights here?

From my research, my gut feeling is that it is either a "stuck open" fuel injector and/or a bad ECU. Since I am an EE, I'm going to open the ECU and see what I find. I have spent way too much money listening to "experts" and am desperately trying to fix the car myself this time. I plan on pulling the ECU out and checking it out tomorrow AM. I'll let you know what I find. BTW -- I did get the codes by shorting pins E1 and TE1 on the diag port and obtained a 24 (IAT sensor) and 32 (Airflow meter). Upon further research, I found that one of the pins on the MAF sensor was pushed back. Repaired the connector by pusing the wire back into the connector. Still need to verify Intake Air Temp sensor functionality -- any insights from the experts out there? The MIL is not on and no codes at this time.

On the same vehicle, it is overheating. Lower radiator hose is not hot while the top one is --- suspect stuck closed thermostat and/or clogged radiator. Will update you all on this as well.

ISFFUN

iTrader: (4)

Has anyone made the repair by soldering new capacitors in? I tried searching for "H9123" which is what's imprinted on the side in those pictures but couldn't find anything.

From this - I think I found that H signifies 50V capacitance.
http://my.execpc.com/~endlr/markings.html

Also does this only occur on 1992-1995 ECUs?

TechGreek

iTrader: (4)

Just letting you know, that EXACT capacitor is the same one on mine (C103) that popped downwards, luckily it only hit two traces and hasn't shorted anything else yet, I'm about to desolder it and find a replacement capacitor.

Tabaka

iTrader: (8)

If someone knows where you can buy the correct replacement capacitors let me know. I have a decent amount of experience soldering electronics and such as I repair digital turntables and other audio equipment.

TechGreek

iTrader: (4)

I traced it out to the vehicle speed sensor on the harness, go figure (transmission issues with OD, no wai!). Now to find the cap laying around

Before:



After:



Bad Cap:

TechGreek

iTrader: (4)

Replacement

http://www.radioshack.com/product/in...ductId=2103610

I'll see if I can find one locally, so I can test it tonight ^_^

TechGreek

iTrader: (4)

I just went ahead and replaced the other one for the EFI Main Relay, as it had started to leak a little bit - it might explain the curiously bad gas mileage, and overly rich condition.

I don't see any other bad ones, and due to a birthday party I couldn't get to it tonight, tomorrow I'll post results

TechGreek

iTrader: (4)

I used some 50V 100 μF capacitors in place of the original 10 μF 50V. I know, I know, bad idea but it's working at the moment and my CEL is gone for the EGR too.

Car is def smoother running, no more ping.