For my entire LS ownership of 12 years, I have been annoyed with an intermittent hesitation upon accelerating from a dead stop or just cruising on a highway. Accelerating feels like a "dead spot" on the accelerator with "no response" at all from stepping on the gas. Mileage is currently at 160,000 miles, with the mass air flow sensor, spark plugs, and all vacuum hoses being changed around 130,000 miles. At highway speeds, intermittently, it feels that the car just loses power and I need to step on the accelerator to regain speed. I've learned to live with this because it may not occur again for months and performs normally. I've attempted a decade ago to have Lexus look at it, and they were unable to find anything. There are no codes showing up other than P0440 (Evaporative Emission System) which was pointing to my charcoal cannistor. Most recently, it has been hesitating very frequently and can almost be dangerous when trying to cross intersections etc. I've read a number of threads pointing to the Throttle Position Sensor as being a possible culprit. Also, I've never cleaned the throttle body, as another area to address. The TPS is $73 and needs to be adjusted after install. I know my car's accelerating is based on "Drive By Wire" and there are a number of components involved, some being quite pricey. Anyone out there with any ideas or a similar scenario with their car? I don't mind investing in the TPS and throttle body cleaning, but I've always hated throwing money at an old car with no positive results. Thanks all.

 

Instead of throwing parts at it hoping for a fix you should spend the money on a professional diagnosis. Any diag shop that's reasonably good should be able to definitively find the issue quite quickly.

 

Unfirtunately the LS430 has very few modules to allow diagnostic equipment to be of any help. Unless the car misbehaves while it is hooked up while driving and shows an irregularity while being monitored, finding the culprit can be a long term costly project. For the present my car’s functioning has been acceptable, while frustrating. I’m not giving up the ship and hopefully I’ll get a lead in the right direction. My Indy told me today that the TPS would probably not be the answer as a failing one has consistent characteristics and is not intermittent. To be continued.

 

Any fault that throws a code is stored and can be accessed though the OBD2 .
Go to a place that has a decent reader .

 

Just ran through a supposedly $10,000 reader.. Just the same two faults. 1) PO440 Evaporative Emissions System and 2) Steering Column not communicating... my steering column motor hasn't worked since the original purchase. No other codes!! as mentioned... There are very few modules in a 22 year old car that will show anything useful.

 

Do you still have your old MAF sensor? Might be worth cleaning it and reinstalling it to see if that fixes the issue. My car used to do the same thing and it was a very dirty MAF.

 

Thanks for asking.......Replaced the MAF a few years ago with a New Denso MAF from Rock Auto...

 

I would take a look at the throttle body. It's possible for enough carbon to build up and cause the throttle plate to stick. It's a stretch but easy to check and clean.

 

Evap system faults can cause your issue. Fix that.

 

Thanks Jharris400. That was one item I was considering. Will be looking into the throttle body cleaning during my next visit to my Indy. Thanks.

 

Great, I'm having the same issue and bought a NEW throttle body. While it looks easy to replace, I've heard both ways that it can relearn after you drive and some say you have to reset before driving.

 

Two things fixed my issue with this: Replaced MAF sensor and replaced PCV valve.