Acceleration Hesitation with Traction Warning Light

[ChrisInRaleigh]

Hello friends,

I have a 2001 GS300 that has a problem with acceleration hesitation. When it has the problem, I see the traction control warning light flash on the dash for a few seconds. I also hear a "thunk" from the rear of the car.

This happens most often when stopped, and especially when facing uphill. If I touch the accelerator too lightly, the car may not accelerate at all, even with the pedal pushed to the floor. I have take my foot off the accelerator pedal and wait until the traction light stops flashing before trying again, otherwise no response. When I press more assertively, the car will usually accelerate, but I still hear the "thunk" and see the traction light flash and the acceleration hesitates.

I did try replacing the left rear height level sensor with a salvage part. It sorta maybe helped for a while but is now back to where it was.

Anyone know how to fix this?

Thanks,

Chris

[Bykfixer]

Can't explain the "thunk" but it sounds like your car thinks that a wheel is spinning faster than other wheels as if you have a traction issue. The system in the car then throws it into what some call limp mode. It reduces accelaration ability in order to compensate for the so called spinning wheel. 

Do you have an ABS light lit? A CEL? Or is it just the VSC light? The traction control system uses info from the anti lock break sensors to give feed back to the transmission and the engine monitoring computers. They decide how/if to adjust things to control wheel spin. 

When I first read your quest I wondered if the Lexus had a hi/lo set up in the differential and the "thunk" was it going in and out of high range like old 4 speed dump trucks used to do, essentially making them 8 speed trannies but that does not seem to be the case. I'm new to Lexus so this quest had me going "hmmmm, what could it be"…… Sorry I can't provide specifics. 

I wonder if perhaps if it's simply an old fashioned broken axle with the smart system kicking in thinking you are driving on a wet dirt road……

🍿

[ChrisInRaleigh]

Thanks for the reply with other things to look into. I have an appointment with a Lexus dealer service this Saturday, but am still holding out hope that someone here might be able to shed some light on the issue beforehand.

 

[Bykfixer]

Any updates to share? 

[ChrisInRaleigh]

Not yet. Taking it to the dealer tomorrow morning for a diagnosis.

[Bykfixer]

😎 

Best of luck. A lot of dealers have really good mechanics. Sales people and the parts guy? Not so much, but often times the younger mechanics are excited about working on cars and the older/wiser mechanics are there to keep them in check when need be. At least that's been my experience at various dealerships. 

[ChrisInRaleigh]

Just got back from the dealer. Diagnosis: Brake booster malfunction. When foot goes off the pedal, the actuator is taking a long time to disengage. This does not allow the gas pedal to work, because the computer is confused into thinking the driver has one foot on the brake and the other foot on the gas simultaneously. The brake pedal always wins that contest.

Note: I only drive with one foot, with the exception cars with manual transmission! I learned to drive in a Volkswagon Squareback.

The dealer quoted close to $4,000 to do the entire repair. The quote did not break out labor from parts, but when I checked with my go-to mechanic, he said they would charge about $400 labor to put "it" in, whatever "it' happens to be. The part itself must be exorbitantly expensive?

That's when things got interesting: My local mechanic tried to look up "brake booster" as a stand-alone part and could not find it. The current thinking is that (perhaps) this is an assembly that includes the brake booster? I need to research this more.

I did find some possibilities on ebay, including these:

• https://www.ebay.com/itm/01-05-OEM-ABS-Module-Brake-Hydro-Booster-Master-Cylinder-Pump-Lexus-GS300-GS430/402599096559?fits=Year%3A2001%7CModel%3AGS300%7CMake%3ALexus&hash=item5dbcc6b0ef:g:XGoAAOSwlXJf0hit
• https://www.ebay.com/itm/98-05-LEXUS-GS300-GS400-GS430-AISIN-ABS-BRAKE-BOOSTER-MASTER-CYLINDER-OEM-X5318/254860792391?fits=Year%3A2001%7CModel%3AGS300%7CMake%3ALexus&hash=item3b56e31247:g:O0kAAOSwqBZgIYY8
• https://www.ebay.com/itm/98-05-LEXUS-GS300-GS400-GS430-AISIN-ABS-BRAKE-BOOSTER-MASTER-CYLINDER-OEM-X5130/254873710361?fits=Year%3A2001%7CModel%3AGS300%7CMake%3ALexus&hash=item3b57a82f19:g:zxoAAOSwfwlgEbiC

Not sure how to identify and find this mystery part. Can anyone provide any suggestions?

 

Perhaps if you order it OEM is comes as an assembly and that's what makes it expensive?

 

Or perhaps if you can get the part by some other fashion, the assembly can be upgraded?

 

That's what I've got right now... Thanks for any tips.

 

P.S.: The Lexus guy did suggest (if possible when driving) to take a few seconds between releasing the brake and pushing the accelerator. I tried, and it did seem to help, but not completely all the time.

 

[Bykfixer]

 

A new Lexus one is over $3000 retail. $2200 at lexus parts now and $350+ for used at eBay etc. 

Check out this video to see why $400 to swap the part. A lot of work to do it correctly. 

 

[ChrisInRaleigh]

Thanks, I'll check it out!

Quick update: The service personnel may have gotten the part wrong:

• The full assembly (called ABS Modulator Valve, https://parts.lexus.com/p/Lexus__/ABS-Modulator-Valve/63090874/4705030220.html) costs $3K
• But the actual repair needed was cited as just the "brake booster" which is a part of the assembly

When I called them back, my service rep said he would make sure which part was actually needed based on the pulled codes. It may just be the "brake booster" part, and that's considerably less expensive. I'll find out more on Monday.

I'm ready with eBay parts either way. I just need to know which one.

I doubt I'll do the repair myself... I can turn a wrench, but for important things like this, I prefer a professional ;-)

[ChrisInRaleigh]

Just got the news: The whole assembly is needed. That will be used, for sure. New it's over $3K.

Or, a friend suggested spraying contact cleaner liberally on the existing assembly's various contacts. Will try that next.

[ChrisInRaleigh]

Found an assembly on eBay for about $360. Communicated with the part guy who said its always a risk to buy a used part, but added they have not gotten this part returned for the hesitation issue. Guaranteed for 30 days. 

Now I just need to decide if I'll have my regular mechanic install it for around $350 or wait for a buddy of mine to help me put it in since he's got grease monkey experience.

[Bykfixer]

Great that you found one. 

If you feel up for the challenge and can take your time swapping it out it sounds like a fun little project. But if you need the car to get around asap it would probably be good to let the pro handle the job. 

Thanks for the update. 

 

[ChrisInRaleigh]

Took a long time for the repair to get done, because my gas tank started to leak, so that took priority. It turned into a weeks-long ordeal.

There were two tries to get a new gas tank. Requesting one from inventory requires a certain number of days, and then it needs to be tested. The first one failed the diagnostic test. So then I had to wait for a second one. From there, the repair got delayed further by rusty bolts and straps on the way to removing the old tank. More waiting for replacement parts for the rusty straps and bolts. Then came the day to transfer the sending unit and other items from the old tank to the new one, but those fell apart due to age. More waiting for replacement parts. And then, finally, the gas tank repair was done!

Putting the new brake assembly on was easy compared to the above.

Result? MUCH improved. But under some circumstances, the problem still happens. I found this disappointing. I also have an engine light on now, so that needs to get checked out. This story isn't quite done yet...

[Bykfixer]

Way to hang in there. 

I had a Prelude that kept having issue after issue. I fought that car for 3 years and finally had it running proper. Soon after I discovered a previous owner had dumped some kind of concoction in the coolant system I was unaware of. So after a routine coolant system flush it began losing coolant from the exhaust pipe. That was it for me. 

My goal was for it to reach 238,000 miles and it took a year to get it running well enough to get from 237,925 to that magic 238. As the odometer turned to 238,000 the check engine light came on. Random misfire and knock sensor again. When I returned home it had lost a quart of coolant in a 5 mile jaunt. 

Nearly $10k into the project of restoring it stem to stern I donated that damned car to charity. The best two days of owning that car were the day it arrived and the day it went away on a roll back truck. 

I sincerely hope you have better luck with your project. 

[06gs3uzfe]

i hope you already resolve the issue with the hydro pump. Have you check on the brake switch? if it' not release right away when you let off the brake pedal; you will have a delay timer here! and this can be your issue the entire time.