Limp mode issues

[Tomakazi21]

I am having issues with my 98 Ls400 that are alike many of the issues I have seen others have but I cant pin point it. I can start my car up just fine (although sometimes it smokes a little excess) and drive down the road and it runs perfect until I hit the throttle right and or get to normal engine temp and then it goes into limp mode. Sometimes it will shut itself off and sometimes it makes it home. If it shuts itself off it wont start for hours until its cooled down fully it seems. Sometimes I go to start it and have to turn the key a few times and even give it some gas to keep it running because it will roll over perfect and fire up just long enough to shut off. I do get the vvt code when the light comes on and I have changed the solenoid, checked the ecu, and am almost certain it is not a fuel issue. My buddy checked the timing when he had it apart at one point and said the belt had a little slack so I have the timing kit and I am going to do the job but I am wondering if there could be a simple fix beforehand. I also had a mouse chew my knock sensor harness previously and after we replaced the sensor and rewired the harness it was great until the whole limp issue come along now the knock sensor codes come back sometimes could it be timing related? TIA sorry for the novel

 

[sha4000]

How many miles do you have in this car? Sorry I don't believe there is any quick fix. What particular code were you getting for VVT-I? I would definitely go back and check the knock sensor wiring if the code has come back. Maybe that mouse is back chewing more stuff up.

[1990LS400]

A number of component problems can cause limp mode.  The only time it happened on my similar 2000 LS400 was when either the pedal position sensor (PPS) or throttle position sensor (TPS) started to fail.  There are instructions in the repair manuals on how to test these sensors.  The sensors are rather expensive so you don't want to replace them blindly without confirming that they are defective.  It my case, one of the sensors was intermittently failing (I forgot which sensor) and the other shown signs of weakness when tested.  I went ahead and had both sensors replaced by an independent repair shop that specialized in Lexus vehicles.