Bocatrip

I have been a member of this forum since 2006 with many issues resolved from fellow members. However, I have had a serious problem since the purchase of my 2001 LS430 7 years ago that I just can't fix. I purchased my car with 98,000 miles and it currently has 125,000 miles. It is a base model with Nav. My car is serviced religiously. I will be at a stop light and when I step on the acceleration, nothing happens. There is a pause and then by stepping again, I usually resume as nothing ever happened Also, I can be freeway driving, and out of nowhere, the car feels as if there is no power, and starts decelerating. I will step on the accelerator one or two times and once again it resumes accelerating as if nothing ever happened. These symptoms have been intermittent over the years and sometimes would not reoccur for months. Lately they are happening fairly regularly and every day. The check engine light never comes on or are there any codes showing up. I have read all the threads on this hesitation issue, on this forum to get any ideas and have read about some of the following being a possible but not a definite cause. TPS (Throttle position sensor) MAF sensor ( I had mine cleaned, not replaced and checked by Lexus with no findings, APS (accelerator position sensor which is part of the drive by wire system), failing fuel pump, throttle motor for the throttle body, bad injectors, disconnecting the battery for the ecu to recalibrate, etc. Of course I have not replaced any of these parts as it can be expensive and a shot in the dark. . I came close to replacing the TPS but was told by the Lexus service manager they never go bad. Trying to accelerate with no response can be unsettling. There are many many posts about this problem, but very few have found a fix or have kept their car long enough to see if it has worked. One member said replacing his TPS by the dealer in 2010 did work, but I was not able to reach him to find what the long term showed. If there are any brainiacs out there that can make a suggestion or point me in the right direction it would be more than appreciated and you might become a God to Me! I love my car and don't want to give it up. I've spoken to Lexus service managers and shops techs at Lexus to no avail. P.S. I always used high test always and techron a number of times. PLEASE HELP!!!!!!!!.

rkw77080

Intermittent problems are the worst kind to troubleshoot. I suspect your problem is related to the drive-by-wire system - perhaps a loose or corroded connection. I would unplug, clean, and re-seat all electrical connections related to the throttle body and the accelerator pedal. CAUTION - please use extreme care when working with electrical connectors, as the aging plastic latches can be very brittle and can break easily. Attached are some troubleshooting procedures you may consider.

Bocatrip

Thank you RKW as your diagrams could be very helpful. If my indy shop is willing to look into it that would be great. My tech there happened to be the service manager at Lexus a number of years and does know these cars. I'll be bringing my car in next week to get my front brakes and rotors changed and see if he has any additional ideas. Thanks again.

LS430FL

I cant stress what rkw said enough. The connections on my 2001 430 were VERY brittle. When I did the valve cover gaskets it was a nightmare some would just fall apart with a touch!

Bocatrip

Thanks LS430FL. You are absolutely correct. The biggest enemy to our cars as they age is how the heat cooks the electrics and here in Florida it's that much worse! When trying to diagnose a problem and having to check certain systems and parts, there is what we call "collateral damage". This occurs when looking for the problem and taking things apart, parts start breaking in the mechanics hands, regardless of how careful he might be. Then we have the expense of replacing these parts. With regards to the great diagram and instructions to check the throttle body (thanks again to RKW).........there is a fairly significant amount of labor and time involved in going that route unless I happened to have the expertise to do it myself, which I obviously don't. To check each individual part with be prohibitive in cost if taken to a shop, especially a dealership. I stopped by Lexus today and spoke with the shop foreman and his top tech that works on LS430s fairly regularly. He told me, the only feasibly way to diagnose my problem is once again having it to occur regularly so that he can hook it up to his diagnostic tools to see it while it's happening. Yes he could find it if left with a limitless amount of time allowed to investigate. Not on a $7,000 car! The problem with the LS430 is there are not enough sensors/modules to trigger the engine light to go on and locate the codes for a repair. I was told the newer cars have hundreds of these sensor/modules and it's easier to diagnose. My best bet at this time, is wait for the car to either crap out or CONSISTENTLY have the hesitation. It's an intermittent electrical problem involving the fuel system, but it's still an electrical gremlin.......the worst kind of problem to have on an old car.