Hey guys,

I have a '01 GS300 that just recently started acting up. Basically what's happening is when you take off from a full stop the car will hesitate and loose power. It will eventually pick up power again but it can happen in the most inopportune time. It's my son's car so I haven't driven it at ton but when I test drove it I almost killed myself because it lost power as I was turning in front of traffic. It doesn't seem to happen when you are driving regularly. So far I've only had it happen when starting from a complete stop. Nothing has been changed with the car in quite some time. There are no error codes to look at and I've already replaced the MAF from RockAuto hoping that might have been an issue but although it seems to have possibly helped it's not fixed. I have it at a Lexus independent shop right now and he isn't finding the culprit either. He found a couple small things like a bad vacuum hose and the loom around the O2 sensor next to the exhaust manifold was missing but fixing those haven't changed anything. He said he checked the Throttle Position Sensor and at least at idle it seems be working fine.

I'm looking for any suggestions of what to look at.

 

I have a 03GS300 and have been battling this same condition for awhile now. I too replaced my MAF from RA, but ended up cleaning my Denso and putting it back in. I also seem to have leaks in my air intake system. I am at the point now with my stock air intake system to replace it with the HPS cold air intake with a heat shield. The resonator alone is around 145. One tube and a cone air filter seems better for me at this point. Now I am getting the VSC VSC off and ABS light. Cleaning the Denso MAF got rid of my lean code. I did replace a vacuum line from the resonator and put real hose clamps on that.

 

You might check the resonator connector pipe (from the air filter to TB) for leaks. The plastic bakes over the exhaust and cracks the resonator box perimeter. Remove the metal shield for best visibility.

 

Don't know how many miles you had on the car and how clean the fuel was.

It's likely the fuel filter is clogged up and slow to deliver enough pressure for start from dead stop. Once the car is going fuel pressure is steady and not a problem.

 

cone_killr great info. My resonator was completely cracked and had a hole in it. Flex seal tape and spray to seal it up. I also had a hose come off the air box in the front. Reconnected and changed the hose clamp.

 

Update: The mechanic I have it at saw that the Throttle Position Sensor might be not receiving a signal like it should at times when giving it throttle. We went ahead and replaced that and thought it might have been fixed. He wanted to drive it around some over a couple days to confirm. He cleared the ABS codes and then drove it some this morning when the ABS lights all came back on and it started hesitating again. Now the correlation seems to be a faulty ABS module that is kicking on the traction control. He is going to put it back on the rack and look for any loose suspension and/or sensor wires but he thinks we are going to need to put on a new ABS module. Also know that he scanned the codes for ABS light and it was saying it's a bad ABS module and front wheel sensors. Hopefully the ABS is truly the cause and can get replaced without costing me a ton. Still I'm sure it's going to be way cheaper than selling the car and trying to find something else.

 

The ABS module is part of the brake master if I remember correctly. The new part is like $4000 from the dealer with no aftermarket options. Look for a good used part

 

It is part of the master cylinder. Mechanic's cost on it from Lexus was just under $1k. I found some used on eBay for about $300.

 

Update #2: So, it's finally fixed. I'm going to give a bit of background and then explain what all happened in case it helps someone else down the road.

Backstory: This is my son's car and a few months back he was driving and the driver's side ball joint failed and we had to drag it up on a trailer to get it home. I replaced both ball joints but what I didn't know until afterwards is that I was supposed to remove the ABS sensors out of the hub before doing the replacement so it wouldn't rip or break a sensor wire. Come to find out they are fairly fragile. The OEM ones are pretty expensive compared to aftermarket ($45 vs $300 a set) so I decided to gamble and installed some that I bought off of eBay. I ended up only replacing the driver's side assuming it was the one that failed because of the ball joint failing. The car seemed to drive just fine but the ABS light on the dash never went away. I eventually decided to go ahead and replace the passenger side sensor since I already had it assuming that since the OEM and aftermarket had different OHM readings that I need to get them consistent. I was hoping that would make the ABS light go away but it wasn't too long after that my son told me about the occasional hesitation.

The first thing I decide to change was the MAF since the car had almost 200k, looked original, and they only cost about $55. Still no change with that. I then started looking into replacing the Throttle Position Sensor but when I read up about it you have to use an OHM meter to find the right spot of where it needs to be installed or you can use software (I believe Techstream) to calibrate it. That's when I decided to take it to a mechanic that has all of those tools. It took a while to do some troubleshooting because it would not hesitate consistently. The mechanic thought he could see that at times at full throttle the TPS wasn't reading the change in pedal position when giving it throttle. We decided to go ahead and replace the TPS, again due to age and being original. The mechanic kept saying that it looked as though the traction control was coming on and that's what was causing the hesitation. He was thinking it was these ECU on the ABS module not working correctly an thus causing it to kick in the traction control. That's when he told me to go look for a used ABS module. In the mean time he was going to put it back on the rack and check over all the sensors and suspension to make sure he didn't see an obvious issue.

Well, he found that the ABS sensors where seated in all the way. He said that there was only about a 1mm gap that you really couldn't see by just the eye. He had to really look at it with a flashlight and could barely tell it wasn't in all the way. So, he seated the sensors again to make sure they went in properly. They probably didn't go in as well as they should have because they are aftermarket products. Once he got both seated properly and cleared the ABS code then everything got fixed. His thought process is that being off even just the 1mm it was reading a different speed than the rear sensors and thus the computer thought the car was sliding and would kick in traction control. Either way, it looks like it was all due to the ABS sensors not being installed exactly as they should. The aftermarket sensors did work properly once they were seated.

 

Thanks for the update

 

It’s good to hear you guys got it fixed.