I have owned two LS 430s now and they both do the same thing. If I hold my foot down on the gas pedal normally to accelerate like a grandpa, the transmission goes through first second, third, and once it hits fourth, then bogs down and shifts back down to third to accelerate. Normal behavour?

This is in ECT normal btw

 

Do a soft reset by disconnecting the battery for 5 - 10 minutes.

 

Thanks for your response! I am aware of the "learning" the ECU does and have tried the soft reset several times. If I push the gas a little more then it doesnt do this, only upon light acceleration both vehicles unshifted early.

 

What year?

 

01 and 02 LS

 

Stock air intake?

 

My '01 does this - it seems normal. It did this with the stock transmission fluid, it did this after a few drain and fills, it did this in the winter and the summer.

You can back off the gas pedal just a bit after it shifts to 4th and it'll stay in gear. Or you can accelerate just a bit harder, and the problem won't manifest.

For what it's worth - running 91 octane, ethanol free gas really reduces the frequency of this happening the car seems to be able to make more torque at lower RPMs with better gas.