I have hesitation issue with my LS when going from stop. When gas pedal is pushed the car won't go. If I floor it rpm very slowly goes up then power kicks in. If I slowly press the gas pedal it's less noticeable. It appears to happen when it's warm/hot outside. When it happens the rpm will fluctuate between 100-1000 rpm and sometimes it'll shut off when gas is pressed at a stop. Any ideas? Is it O2 sensor?

So far I replaced the coolant temp sensor, checked the MAF for any blockage or anything out of ordinary but found nothing. Yesterday was cold and I drove for about an hour in stop and go condition and it ran fine.

 

could be the trac system
to find out start the car and check that the track light is off
then take it out on the streets and press on the accelarator
if the car stalls and the trac ligth turns on then its the trac system

 

Trac light is off the entire time. Cel and trac light briefly comes on then goes off immediately when car is about to stall and rpm comes back up.

 

have you checked the engine codes?

 

^
I will do this tonight. So you use a paper clip to bridge T1 and TE1 just above left knee?

Thanks all for suggestions btw.

 

its way easier to open the hood and jumper them on the check connector on the intake manifold, unless your super short and/or a contortionist.

 

No E1 and TE1. See http://www.lexls.com/tutorials/intro/codereading.html for more details.

 

Got code 24 and 31. Also O/D is blinking. I disconnected the maf for a minute or two, would this trigger 31?

24 Is for intake air temp. Is this easy fix?

 

Just did some googling and it looks like IAT sensor is built into MAF am I right?

 

what scanner are you using
will the scanner read any codes if the car doesnt startbut cranks

 

those codes will come up if the maf is unplugged while the engine is running. so leave the maf plugged in, reset the ecu, and drive around the block and check again.

 

I cleared the codes. I think ecu diagnostics will return nothing. But I found this thread
https://www.clublexus.com/forums/ls4...r-problem.html
This describes my exact problem. Will replace fuel pump and see how it goes.

Tony- no scanner is used. Just a paperclip to bridge e1 and te1 above your left knee. Then turn on ignition but don't start the engine. Then watch your CEL.

 

say yeah i found that web site too
i had some recent problems with my 93 ls400 recently and i fixed it
the car would not start i found out it was the fuel regulator
it took me about a weeek and it was a bit tricky because
of post that say if you crack the fuel line and theres fuel then you got gas
but come to find out the fuel regulator(drum looking thing on drivers side) does not allow the fuel to go any further if its malfunctioning