PHX-GS430

Hello again all. So, I finally was able to try a few things out on my wife's car in hopes of getting the response from the pedal back. I have cleaned the MAF sensor and ran a bottle of Chevron Techron through it. We have used only Premium Chevron fuel in it. The air filter is new. Also, the vehicle has 112k on it.

I just saved up enough money to put in all new plugs over the weekend (dealer wanted $429 to do it! INSANE!). They are the NGK Iridium IX. While I was at, I cleaned the throttle body as well and had the battery unplugged so it reset the ECU.

After I had cleaned the MAF sensor a while back and ran the bottle of Techron through it, we got back the downshifting power as initially it would take for ever to gain speed, now the thing is a BULLET!

However, the issue that still exists is the "mushy pedal" syndrome that is sporadic. Sometimes coming off the line, you push the pedal, the car goes no where, you back off the pedal, press it again, it goes. When on the freeway cruising, it feels as though it chokes or as if there is a power loss. You have to take your foot off the pedal and press it back down to get it to go again.

So, after having done much searching on here, the only other things I see are the actual throttle body or the Pedal Position Sensor, the latter of which I am leaning towards. I noticed 3 people with the same year and model have been successful after changing this sensor out. Any ideas how much this sensor runs?

I also found a post about the TIS (technical information system) with the link. I plan on spending the money to check this out to see how easy things are to work on with this motor.

Do you think I should start with the PPS or should I replace the MAF sensor instead, as I only bought cleaner for it? The car has thrown no CEL lights. It's just a frustrating thing that has no rhyme or rhythm to why and when it happens.

Anyone else have any updates on this or any other specifics I should look into?

Thanks everyone!

GS4_Fiend

iTrader: (22)

I think the culprit was the Throttle body motor. I don't know the threads on top of my head, but try searching.

Btw, on GS430, they have electronically controlled throttle. Which they don't use cables to operate. So if you clean it with cleaners, it will kill that electronically controlled motor.

BLAXCGS430

Good Day:

I have the same problem with my 01 GS430 with 96k miles on it. I started noticing this anomaly about 15 - 20k miles ago and took the car to the dealership for a diagnosis of the symptoms. The first symptom I noticed was that the car would shift normally up to about 45mph. Then without warning the car would seem to "brake" suddenly, the RPM's would reduce to almost 1000 RPM and the accelerator pedal would have no pressure in it. I would have to press the pedal to the floor for any response from the engine. The second symptom that I noticed was that the same thing occurred when I was in first gear on occasion. This made for a very dangerous situation. Sound like your situation? The tech at the Lexus dealership that I used to have my car serviced at came up with no explanation for these problems after riding in the car. What he did do, or, claimed to do was to update the cars computer/ECU with codes from Toyota. That seemed to "fix" the car up until a few months ago. Please know that I have no faith in the work of this Lexus dealership. Ironically, this same technician missed the fact that I had a dented rim on my front passenger side which caused my car to shake without mercy at roughly 58mph for a more than a year. That was until a Toyota dealership noticed the problem. Might be worth a try. But at $105 for a mechanics hour where I live...it might not be. I have to make the same decision because my car is back at it again. Smile! If anyone knows of a permanent fix for this problem I'd love for you to post it. I'm very frustrated of $2000 potential solutions from Lexus. Thanks in advance for your time and consideration. By the way, you guys and gals are great! I've found out more about my car on this site than I ever have at Lexus with any of their factory "trained" technicians. Keep up the good work! My thanks to all for the information that you've shared.

timgs300

iTrader: (22)

This all sounds like the throttle position sensor. I had a 98 with 66k and it did the same thing. You push on the pedal and nothing. Then it would be ok. Then again out of the blue - nothing. . It's a potentiometer, therefore, you can sometimes push and nothing or hit it in the right spot and it will do something. Funny like that. If I had this symptom again, I would replace the tps without hesitation.

BLAXCGS430

Good Day:

First of all, thanks for all of the responses. I agree with you timgs300. After searching various posts this seems like a great place to start. I also found a post that indicates that these symptoms may be caused by a $4 - 13 part that often goes overlooked. It seems that the Positive Crankcase Ventilation System(PCV) valve grommet could be the culprit. Often the PVC hose becomes full of debris and needs to be cleaned or replaced. The cleaning/replacement of this hose and the replacement of a cracked valve grommet has seemed to be a cure for other members experiencing the same problems. I think I'll start cheap, or free, first before I get to the expensive stuff. Does anyone have an opinion on this hypothesis? What do you think timgs300?

timgs300

iTrader: (22)

I am very skeptical of that. However, I'm always game for something easy and free. A new pcv valve certainly can't hurt anything. Supposing it was stopped up. Crankcase ventilation would cease. Would that cause air to stop moving through the intake hose and throttle body? Doesn't seem like it.

PHX-GS430

Yes, those are pretty much the same symptoms I have experienced. The first where you are cruising along on the highway (foot on the pedal at a constant coasting speed) and all of a sudden it feels as though you would have thrown the car into Neutral and the car begins to lose speed even though you haven't moved the pedal at all. You then need to take your foot off of the gas to release it and then push back down to get it to respond and get it back up to speed. It does this for no reason what-so-ever without any indication at all.

The second situation is probably a little more frequent, but the same. You are sitting stopped at a light, car feel fine, idling normally, ready to go. Then you take your foot off the brake, press the gas and it fits like it's stuck in mud, doesn't want to go anywhere. You need to once again lift off the gas, then hammer it back down and get it to take off. This indeed can be a very dangerous situation if you need to get out of the way very quickly.

Like I have mentioned, I cleaned the MAF sensor (not sure if it is worth trying to replace) or just go to the Pedal Position Sensor first.

I concur 100%! This site and forum has been superb. I love all the feedback, opinions, help and education on these vehicles, especially as I had never owned a foreign brand car before.

GS4_Fiend

iTrader: (22)

Like I said, there is a thread about the Accelerate Position Sensor. It ended up being the throttle motor which is the Electric Motor for the throttle body. Try looking for that thread, it may help you. I doubt it's the TPS.

PHX-GS430

I found one result from October 2007 when searching for "Throttle Body" in the GS Forums and the result for that user (Luxor) was also the Accelerator Pedal Position Sensor.

i-am-having-throttle-position-sensor-and-throttle-motor-problems

GS4_Fiend

iTrader: (22)

As we state things, we can't confirm it until we check out the sensors. If you know how to check the voltage for the sensor. That would be your best bet. GL.

slickgt1

iTrader: (1)

OK, Nope to all of you. My old thread
https://www.clublexus.com/forums/gs-...-diagnose.html
Yea it sounds like the maf is messed up on your car. I am telling you, same symptoms as my car had.

PHX-GS430

I've got a voltage meter but do not know the specs of these sensors. Where could I find information on this? I assume the TIS site includes electrical components and the correct voltages?

At this point, this may be the next step I try because I have sprayed it with MAF cleaner and while it got me back the hard downshifting power, I still have issues with off the line slow and while at a cruising speed where it just feels like I turned off the cruise control switch and it just starts coasting slower.

From what I have found online, it looks to be $140, does this sound about right or the best price online. I assume the dealer is well over $200.

PHX-GS430

Also thanks to everyone for continuing to chime in as well as the links to the other posts to read, compare, and see eventual solutions.

GS400KY

had this same problem out of my gs400 ended up being throttle control motor found a new used throttle body off of an ls400 problem fixed!

PHX-GS430

Been quite a while since I've posted but wanted to give an update on this specific problem.

We took it to the dealer last week and they experienced the issue but only wanted to replace the MAF sensor and clean out the carbon on the heads. They told us no codes were thrown so there was no way to tell what was causing the issue.

However, they also told us we needed a new timing belt right away. The car has 115,000 miles on it and it should have been changed back at 90,000 service (before we bought it).

I have never had this service done to any of my vehicles and I was not planning on a $700 service. However, after learning that if the belts goes, so goes the motor, we had it done (scared into more like it) along with the coolant. As this was way over our planned budget for a couple new sensors, we had nothing else done.

However, I purchased and replaced the MAF sensor with no success at resolving the problem.

This leaves us down to 2 sensors, the Throttle Position and Pedal Position. The problem now is we are wiped out financially so it will have to wait. However, are these two sensors easy to swap out? I have no problem doing the work myself if I knew where they were both located.

I have found the Throttle Position sensor online but not the Pedal Position sensor.

Any more stories or updates on this known issue from anyone? I appreciate the continued replies!