DonCorleone

iTrader: (6)

Hey William, I know your LS4 is totalled/being parted but here are some pics of the same year ECU (mine is a CA version, though) in case you or someone else wanted to pursue it further. I can take more pics if you want a shot of a specific area.

https://www.clublexus.com/forums/ls4...ml#post6352095

Thanks for the ATE warning, they were one of my repair options, I will cross them off the list.

williamb82

bump to warn people to stay away from ATE!!!!!!!!!!!!!!!!!!!!!!

espalding

For anyone who wants to see how to professionally fix a circuit board (pcb) trace, here's a decent YouTube video on how to do it and what tools and supplies are required.

http://youtu.be/TFcPxCN93nY

cobalt91

Wow, that dude has got some steady hands!

espalding

My 93 LS400 has been plagued with the same dreaded problems... stalling, hesitating, bucking, rough idle, etc. The problem has been exacerbated by ambient temperature (hot) and humidity, I'm in North Carolina.

Problem: after a hot evening thunderstorm, the next day will be 95 degrees and 90-100% humidity and the old LS will run like crap. While idling, it will intermittently stutter as if it's brain and power has been interrupted a micro-second constantly (even the power to the brand NEW fuel pump will stutter with it). When driven it does this intermittently, like hiccups, at any speed. From a stoplight start I feel like it's going to cut off but never does, it just hicupps, limps off the stoplight and then just takes off like a racecar, then it'll hiccup, hiccup, drive normal, hiccup, etc. During the hiccups the CEL comes on but turns off after a hiccup. IT NEVER THROWS A CEL code!!! I get the all good flashing CEL when trying to pull the codes or sometimes I get nothing, not even flashing CEL. I've had this car since 94 and in past years, I've been able to get codes, but nothing with this problem.

Oddly, it will run really well on a cool dry night, almost no hiccups, stalling, just a slight hesitation during initial acceleration from a stop.

RECENTLY REPLACED:
Plugs (NKG)
Plug Wires (NKG)
Both Coils (DENSO)
ECT (engine coolant temperature) Sensor (AUTOZONE)
Fuel Pump (DENSO)
Fuel Filter (FRAM)
Fuel/Injector Treatment (Berryman's)
Tested MAF(within specs)

I have decided that everyone is pretty much correct that the problem is with the ECU (Capacitors).

In my particular case. I pulled out the ECU based on what everyone was saying here on the forum and discovered that overall the boards were in excellent shape including the capacitors. But, I did discover a burnt resistor R202 and circuit traces that appear damaged at a pass thru solder joint. Check out photos of my ECU and the one pic with another member's ECU inserted to show the difference in the R202 resistor area.

I have shipped my ECU to autoecu.com (Automotive Scientific Inc. - ASI) for diagnostic and rebuild/repair for $149 + $18 S&H. I chose ASI because other members recommended them and they offer a warranty on their workmanship. Also, I used PayPal to order their service, which PayPal has a great customer refund protection program. So, I will update after installed.
Flickr Image Links:










http://www.flickr.com/photos/8343569...in/photostream
http://www.flickr.com/photos/8343569...in/photostream
http://www.flickr.com/photos/8343569...in/photostream
http://www.flickr.com/photos/8343569...in/photostream
http://www.flickr.com/photos/8343569...in/photostream
http://www.flickr.com/photos/8343569...in/photostream
http://www.flickr.com/photos/8343569...in/photostream
http://www.flickr.com/photos/8343569...in/photostream
http://www.flickr.com/photos/8343569...in/photostream
http://www.flickr.com/photos/8343569...in/photostream

espalding

***** UPDATE *****

All my crazy LS400 problems seem to be solved!!!

I just got my ECU back yesterday from ASI (AutoECU.com) for my 93 LS400. ASI was great to work with, easy instructions for sending the ECU and I like their website because you can track the rebuild process in stages and then track the shipping of your ECU back to you. It took 11 days from the day I dropped it off at Staples for the UPS guy till it arrived on my door step (it was shrink wrapped and packaged very well). The ECU has warranty tape on the sides, so if you try to open it, it will void their warranty.

I just installed it, topped the battery off with a fresh charge. BTW, it is 84 degrees and 100% humidity. Normally, when it is sunny, hot and humid, idles and runs horrible with hiccups, stalls, shudders, etc. BTW, it is overcast, 84 degrees and 100% humidity today, so should be a pretty good first test drive.

1. It cranked perfectly
2. Idled perfectly for 15 minutes without a single hiccup.
3. Test drove, it hasn't drove this well in 5 years!!
4. It doesn't hiccup, stall, shudder and the hesitation off a stoplight seems to have disappeared.
5. It even shifts smoother
6. Acceleration seems to be better.
7. It will now accelerating from a stop with the AC on and not hesitate out of the gate. (this was always annoying in hot weather)

I'm cautiously excited, I still want to see how it performs under the hot (95-100 degrees), sunny, humid weather in the south. I'll post updates. But, for now, it seems that ASI did a great rebuild job on my ECU for $149 bucks. I finally got my old Lexus back again!! Thank you ASI!!!

freegard

WOW!!! Well my 94 LS 400 is doing exactly that-accelerates fine as long as I dont push it; push it and it acts like
its governed at 2K RPM.
I already replaced 10 Electrolytics in my instrument cluster and it works fine now. Looks like I will be spending the next two days replacing the polarized low temp electrolytics in the ECU with mil grade (115 Fahrenheight rated caps) before I even bother trying to look elsewhere; that is based on empirical knowledge and a little extrapolation from posts like the ones here that project a logical rational thought train.

I would like a tutorial on removing the ECU. Can anyone help me with that?

freegard

Well, what is the ohm value of R202?

Yamae

All you need is just to see those color rings. It's 623. The last 3 means the number of zeros though.
Incidentally I have never seen MIL spec 115 degrees Fahrenheit low ESR electrolytic capacitors. Where can you buy them?

espalding

Hey everyone,

Well, it been pretty much 3 months now and my 93 LS400 is still running LIKE NEW ever since I had ASI (AutoECU.com) refurb my ECU for $149 bucks. We (North Carolina) even had some scorching hot and humid days in August and it cranked and ran like the day I purchased it. That was the ultimate test and would've been when the original problem show itself the most.

I took several road trips at the end of the summer and the old LS400 drove great, acceleration is back, it shifts sooner and smoother and has a noticeable improvement in gas mileage during road trips.

I have to say that I thought this problem was pretty much the end of my 93 LS400. I had tried pretty much everything suggested here on the forum (i.e. ECT sensor, throttle body, etc.) and the ECU refurb was my last resort. Best money ever spent on a single part or service!!

I would suggest to all LS400 owners with a vehicle over 15 yrs old and are you're starting to experience the tell tales signs of ECU (Capacitor/Electrolytes) issues. Go ahead and spend the $149 bucks and have the ECU refurbed by ASI. The LS400 ECU is simple to access (under the passenger glove compartment behind dash panel) and replace. Don't waste a ton of your time swapping other parts chasing this problem, unless it makes since to replacement those parts because the're due or need maintenance (i.e. ECT sensor, throttle body, etc.)

Hope this update helps!

espalding

***** UPDATE *****

It's going on 5yrs now since I had ASI (autoecu.com) refurb my ECU and the car is still running great. I'm about to roll 200,000 miles on odometer and getting ready to completely replace suspension with KYB shock/struts, mounts, spacers, and new dust sleeves. Then new brake job, new tires and front-end alignment. That should get it riding smoother again!!

anesthesia

Great to hear, and thank you for the update. I'm just curious as to what signs to look for when your ECU is beginning to fail on your car? My car is a1999 ls400 drives great now but thinking of one day just doing this refurbished ECU.