Lexturious

I don't post much but I come to read and learn from this form often, however lately my transmission has gotten me stumped. I have been having issues for about a year now however it recently has gotten a lot worse. It started out as just hard shifting into gears and especially when downshifting, and at one point last year it didn't want to shift into any gear so I flushed my transmission with toyota fluid. After that it shifted better but it was still harsh under full throttle but at least it worked for the time being. Now this year its been getting worse and now my car doesn't downshift at all into first but I can get it to go into second gear if I play with the pedal a little and find its "sweet spot" however if I floor it to pass someone it just hesitates and bounces around for a while until my o/d light comes on and starts flashing. This only happens when I push the little button with the gas pedal, otherwise my o/d light doesn't come on at all. I pulled the code and I'm getting CEL code 25/26 and transmission code 67. I'm guessing 25/26 is due to a o2 sensor but I'm not worried about that as much as the transmission since they CEL light just came on yesterday where as my transmission has been doing this for a few weeks now. Its still drive able but who knows for how long. I have been contemplating swapping my auto trans out for a w58 since I've been dreaming of a manual ls400 ever since I bought the car 3.5 years ago. Its a 1990 ls400 and I know my tps sensor isbad or at least tthat's what Lexus told me last year so I ordered a new one the other day and I'm just waiting to get that in the mail. I'm guessing that's not going to fix my o/d speed sensor issue and I'm not even sure if the sensor could effect it that much. My transmission fluid has seamed to darken faster then it usually does after I get it flushed as well. Any help is much appreciated otherwise I'm going to just save my money and hope it lasts till winter when I'll try and do a manual swap. Thanks again

LScowboyLS

a bad TPS sensor can contribute to the transmission shifting issues, as well as a misadjusted transmission throttle cable, as well as failing ECU caps, or the speed sensor, so you still have a lot of diagnosing to do before switching this transmission out, these Aisin A341E's don't tend to break with less than 300k

do you have the Lexus factory service manual, it has a great step-by-step transmission troubleshooting chart!

Lexturious

That's why I figured I would start with the throttle positions sensor as well as the speed sensor but I need to wait till payday for the speed sensor. The transmission throttle cable is up by the throttle body correct? I've been meaning to adjust that but I doubted it could be that because of how intermittent it can be. I was unaware about the ecu capacitors I will look into replacing those next week as well since I have some electrical background the problem is I need my car 7 days a week currently due to my work schedule and my wife's and its our only vehicle currently. I have no issue with the automatic transmission but I know how expensive it can be to replace sensors and flushing the transmission and replacing solenoids can be and it might not even solve the problem. I do have the original manual I just didn't expect it to have much but I will look in the morning. I work at a ford dealership in Mn so I have a decent amount of mechanical background but not with auto transmissions. Thanks again for your help at least now I have some more things to look into

LScowboyLS

yes, the ECU fully controls your transmission, it does not have any controller or intelligence of it's own, the ECU also fully controls the A/C

make very sure you use only the exact brand and model# of capacitors I have listed in post #1 of my how to replace failing ECU capacitors thread, as these are a very special type of capacitor, and I have never seen any professional shops use the correct ones, many of the ECU's I work on have been previously repaired, and none of them have the correct type of special Japanese premium low-ESR capacitors, and so they don't work right, even after replacement!

also keep in mind there is a TPS calibration procedure to properly install it, which is in the factory service manual

Lexturious

Cool thanks again for all the helpful info and links, I will purchase the new caps this Friday and hopefully get them installed in the next couple of weeks. I Dont use my ac since I have yet to convert it over from r12 coolant so I Dontknow if tthat's malfunctioning or not I will make sure to order the correct caps and have them carefully installed since that thread is very informative.

Good to know its in the manual I Dont usually look in there for troubleshooting I usually look online since I know lextreme has a tutorial on there site as well.

LScowboyLS

I don't see any real reason to convert it, R-12 is available, and legal to put into cars that originally came with it, and it actually works better than R-134a.

but not using your A/C will actually harm it more than using it!

Lexturious

How would me not using my ac harm anything? I just figured it was easier to find r134a since you can't just buy r12 anywhere these days. I liked r12 better then 134a but it just seams more convenient to convert it in the long run. Plus I took my car to a small town mechanic a couple years back to get it converted but they claimed to flush the system and refill with 134a and ever since then its been goofy so I'm not sure what happened so I just Dont use it.

LScowboyLS

not using the A/C is very bad for it, seals harden from lack of lubrication, and narrow passages (i.e. the expansion valve) get gummed up and blocked

even people who use their A/C and it is working correctly would be well advised to also use it in the winter (that doesn't mean you become cold, it means you turn the heat up but you are heating up air-conditioned air) and it serves to just dehumidify the air (which makes the interior more pleasant in humid areas) and also keeps the A/C in good working order!

one of the rare cases where the more you use something, the longer it lasts!

I guess the best analogy I could provide is that you don't let your car sit for a year or even several months without cranking it and running it periodically.

Trivia: The A/C compressor is actually a little tiny engine, it is a rotary engine these days, but not that many years ago it had pistons and cylinders, actually!

Lexturious

Yeah that makes sense and I know a lot of seals are already leaking on my ac system since it been leaking ever since I bought the car. It sat for a while before the last owner sold it I think a year or so If I remember right. My compressor is shot anyway and I need to replace it sometime but in Minnesota we rarely get excessive heat for more then a few months out of the year. In other words ac isn't a big concern of mine since I haven't had working arc for almost 3 years now. I mainly just want my transmission working again, I just ordered the caps for the ecu and a buddy of mineis going to help with the soldering since he has a lot of soldering experience.

Lexturious

Alright so I managed to take apart my ecm this morning to see what its looking like inside, however I dont see any major issues that would be causing my transmission problem. I will still take the time and replace my caps once they arive but im not convinced this is my current issue. My TPS will arrive tuesday and on friday I will order my speed sensor and go from there.

Lexturious

A couple months ago my ls400 decided to stop working on the way home from a small road trip (about 150 miles up north from Minneapolis) and my car would no longer shift into any gear. I was driving down the highway doing about 55mph when all of a sudden I had no power to the drive train it felt as though my car was in neutral. So I pulled over and let it sit for a while and tried putting it in L or 2 just to see if it would work and it would go for a few blocks and do the same thing. So I decided to have it towed home and park it until I have more time and money and just drive my winter beater for now. I haven't been able to do anything with it yet since I Dont have the money since I recently switched positions where I work. I'm slowly saving money up again so I can fix my daily driver up however I'm thinking about just swapping over to the w58 since I eventually plan on making this my summer car that I can take to the track. Its hard to find a reliable rwd car that everyone doesn't already have and the ls400 is definitely uncommon to see at the track and is very reliable. The problem is the weight and how expensive everything can be to make it come alive, I'm not looking for anything to extreme but I just want to have some fun. I'm planning on having the manual swap and coilovers installed by march of next year. I was just wondering if anyone who has more experience working with the ls400 has any tips or advice since I know people dont seam to do the manual swap on these cars very often. I have a good idea on what parts I need thanks to research I've been doing for a couple of months and I'm about to start ordering parts I want to start with the clutch/brake pedals and the master cylinder since I've heard they are the most difficult part of the swap due to clearance and moving the fuse box etc. Anyway any advice would be much appreciated and I know I'm crazy for wanting a manual sedan but I have seen many transmission issues on the early ls400's and I miss having a rwd manual car for the summer.

UNCNOR

iTrader: (1)

What is WOT???No glossary that I can find.

Lavrishevo

iTrader: (1)

Wide open throttle. Pedal to the medal...

LScowboyLS

this is a very bad plan - all this attempt at swapping an automatic for a manual idea is gonna do for you is to ruin the car - even professional fabricators would have a hard time with that, this car was never engineered to have a manual tranny

I have yet to see a misbehaving automatic transmission on an LS400 that we haven't been able to solve here on Club Lexus

did you have the capacitors replaced yet?

how many miles on the car?

PureDrifter

iTrader: (10)

lol "professional fabricators" would have no major problems converting an LS400 to manual if using a conversion kit for the trans-1uz adapter.

fitting the pedals and clearancing the firewall are standard stuff. Perhaps if a huge T56 or something were used that are too big for the tunnel there may be an issue but otherwise not at all.