Sportznuts

I have a 1991 Ls400 with 194,000 miles. I have never had a problem with the power or the transmission.......until I had 4 other people in the car. I noticed with a full load, of course there's much less power, but more importantly, the car had a difficult time shifting into a lower gear when going up hills.

Does anybody else have this problem?

Do I need a tranny flush?

PureDrifter

iTrader: (10)

reset the ECU.
if u suddenly load up the car with weight when u normally drive it alone, the ECU has a profile that suits YOU, not the weight of you AND your friends

or just let it go, as you drive with more people in the car the profile will eventually adjust

Sportznuts

I bought the car 1 1/2 years ago with 153,000 miles. The back seat looked like it had never been sat in. Not a surprise. It's usually a 40+ crowd driving the LS400's........historically speaking (please don't jump on me). So it would make sense that the ECU wasn't used to the added weight.

I didn't realize the ECU can get "used to" a certain amount of weight. Makes me think it's like a robot developing human feelings. Maybe this Ls400 is a "small wonder" (80's sitcom)

But Puredrifter, you're the man on this forum so I'll take your word for it.

I've had the car for 40,000+ miles, do you recommend me changing the tranny fluid? Only $70 at Oilstop. Not a flush, just 5 quarts I believe. Not the best idea doing a full flush on a 17 year old tranny.

PureDrifter

iTrader: (10)

meh, if the reset doesnt help, there's no harm in flushing the trans, all those myths about it doing a ton of damage are just that, many members have fliushed their transmissions with no issues. just make sure to use toyota t-iv fluid only.

UCF11

Did you try switching into power mode on the gearbox, it will shift down a gear sooner under load.

Other then that, Reset ECU, Tranny Flush (As said, only use toyota fluid even though it says Dextron 2.

Another thing you can look into is the kickdown/transmission pressure cable adjustment,

Here is an Australian Artical on LS400 Tranny Adjustment.

http://autospeed.com/cms/A_110682/article.html

Autospeed is an Aussie Online Automotive Magazine with plenty of LS400 related stuff.

Let us know how you go.

Sportznuts

Thank you Puredrifter and UFC1 - I have done tranny fluid replacement (2 1/2 quarts only) The car seems to shift a tiny bit better but haven't loaded up the car to really test it.

I always keep the "power" button flipped. I will reset the ECU today to see if that helps.

Thanks guys for your help.

PureDrifter

iTrader: (10)

for the guy who asked how to reset the ECU:
either pull the negative battery cable for a few minutes or pull the EFI fuse.

rsg

I had no idea the 1gen LS had the "learning" ECU. I thought this was only in the 2gens and higher. That would explain the less-than-desirable performance when I first started driving the car. It now feels like a sports sedan (at least when it comes to acceleration).

PureDrifter

iTrader: (10)

yep, it is "somewhat" intelligent in 1st gen cars as well.

Sportznuts

Was that after the ECU reset?