Kidneykitt

I own a 2000 LS400 Platinum Edition with 115k miles. I've had no problems with the car till now, my husband and I where driving about 47mph when the car started jerking almost hiccuping then we started to lose acceleration, we pulled over checked it out didn't see or smell anything unusual. The car started back up fine as soon as we tried to accelerate it started the hiccuping again and having a hard time accelerating. We pulled over again and it stalled out. Called AAA, when the wrecker arrived it wouldn't even turn over. Our neighbor is a mechanic who works on the car so we had it towed to our house. The next day when our neighbor came to take a look at the car she started up fine purring like a kitten took it for a drive around the neighborhood with no problems. Diagnostics came up with nothing. A few days later It happened again to me in the middle of an intersection, I started to panic so I pushed the gas peddle all the way down and a few seconds later it caught on and all of a sudden I was flying and then it would jerk and hiccup again almost to a stop and then repeat, I got it home and hooked it up to the diagnostic machine and Finally we had some codes to go buy P1120 and P1121 which from what I understand has to do with the throttle body. at one point we had it towed to to the Lexus dealership and all of a sudden it started and drove perfect, of course they couldn't find anything wrong with it. They went by what we described and the codes we had gotten and sort of guessed that it was indeed the throttle body. We bought a used throttle body and just had it installed and it barely starts, if it does it struggles to stay on and then putters out and stalls. We have no idea what's wrong with it, has this happened to any one else? Any help would be greatly appreciated!! Thanks!

YoshiMan

To the best of my knowledge, the 98 and up LS400s have the electronic throttle control, which means that there is literally no physical link from the gas pedal to the throttle on the engine, and my guess is that there may be some sort of fault with the electric motor that actually opens the valve.

Do you know if the throttle actuator motor was swapped as well with the new throttle body you put on it?

Kidneykitt

There is a physical link from the accelerator pedal and it is a new throttle motor.
Could it have something to do with the fuel pump or something in that area?

Lavrishevo

iTrader: (1)

Throttle body's don't go bad that often on LS400's. I would start looking at the throttle position sensor. Have someone test it to see if it is in spec. The fact that the problem is intermittent makes things harder. The TPS also have to be adjusted properly. It also sounds like you did not do something right when you swapped the TB. Go back and check everything. Reset the ECU as well.

There also is a cable going to the TB but it is only for a limp mode if the TB fails or the car goes into limp mode.

Kansas

The problem is likely caused by a failing Throttle Position Sensor (TPS) and/or Pedal Position Sensor (PPS). I had the exact same symptoms at about the same mileage on my 2000 LS400 Platinum Series back in 2009. The TPS failed slowly over a few weeks and I barely limped my car to the shop when it finally failed. The PPS tested "marginal" so I had both replaced. There are specific instructions on how to test the TPS and PPS in the repair manuals but it takes some special equipment and mechanical knowledge to test them.

PureDrifter

iTrader: (10)

the cable is a backup, if you start sputtering and push the throttle pedal all the way down, the throttle will open just enough to let you get off the road safely.

quixotic

How much did it cost to replace them?