2002 LS430 with about 160,000 miles. Very well cared for and in excellent condition. Last long road trip I saw 28.2 MPG tank average on I95 so I have to assume all is in very good working order. No issues at all except for strange behavior when mashing the pedal to WOT as if in hard passing maneuver. I will try to explain below...

If leaving hard or passing with lots of pedal input (not to the floor) engine and tranny respond as expected. No issues with power delivery.

Now... Sometimes... If leaving hard or passing with 100% pedal input (to the floor) tranny responds as expected but one of two things may occasionally happen:

1. Engine responds as if the throttle plate is not opening all the way. Feels like a carb with the secondaries stuck shut. Lower power output.

2. Engine seems to respond okay but power delivery is surging as if the throttle plate is coming off WOT. Feels like a Q-Jet carb when the secondaries are too loose and the air doors bounce until they settle.

When I first got this LS the engine was quite a bit stronger than the '95 LS400 I had, though the drive-by-wire thing is just awful. Now the engine feels weaker at WOT. Plenty of power in all other cases but at WOT I swear it feels just as if the throttle plate is not opening all the way. So from idle to 4,000 RPM strong and then weaker from 4,000 to 6,000 RPM. Again feels as if the throttle plate is not opening all the way thus reducing cylinder pressure.

Are the drive-by-wire actuators known for any sort of issues such as I have described above? is there some easy way for me to check if the throttle plate is opening all the way? I did remove associated connectors and spray them with contact cleaner. This is includes down at the pedal as well.

As mentioned above car is in excellent condition and has zero other issues. TPS and drive motor resistance is withing spec. I did not get to the pedal sender yet...

Any help, ideas, or thoughts are greatly appreciated!

 

Clean the throttle body/ maf? But I would do the pedal memory reset first.

 

My old GS/ SC would hunt for gears/ kick down when I accelerate normally up hills, feels like it will shift from 2 to 3rd then back to 2nd cuz it feels like there's not enough torque. I did the pedal reset adaptation and the problem went away, and acceleration is much more lively and throttle more responsive.

 

I will try this next and see what happens. I have a good idle but it does seem low at times.

 

Most likely a dirty MAF. Clean it with MAF cleaner and make sure you clean the sensing wires at the bottom of the black tube. The red bulb is the IAT sensor.