I have not taken it to the dealer yet, been too busy with other things. Hopefully if enough of us complain, Lexus will come out with a fix for it. If anyone does find a fix, please post it.

John

 

95% sure it will be a software fix.

Thats why the dealership can't find anything wrong or fix the problem.

The solution will have to come from Lexus.

Even the best diagnostic shop can't or wont rewrite the software, only Lexus.

 

I agree but I guess they haven't heard from enough people to realize it is a problem or to come up with a fix for it. If you live in a cooler location my would never see the problem but for those of us who live where it is normally over 90 degrees it is a big problem.

 

Ask to go out with them to demonstrate the issue. If they won't, escalate to the regional manager. Call corporate to get the attention and they track the issues. It's tedious but may be the only way to get results.

 

I had the *exact* same thing happen to me in my 2021 ES300h (bought new, less than 10k miles at the time) happen on an unprotected left turn, after the car was sitting. Left turn signal on, traffic clear, I begin to pull out, car creeps forward as I let off the brake, then i step on the gas pedal and nothing. My head lurches forward as I anticipate acceleration but the car doesn't respond at all. After 2-3 seconds (felt like forever) the car seems to "wake up." I posted about it a while ago when it happened.

It's almost as if the computer fell asleep, timed out, momentarily. It happened on one other occasion. I emailed my dealer about it asking for an appointment and they never responded (they had responded to other emails before). I sold the car and never determined what it is or had it fixed.

 

Well I believe I have found a solution to the stumble and hesitation problem when the engine is very hot. As I said in my first post, I always use 92 octane gas in the car but I was always buying my gas at a local BJ's Wholesale club as it is only a 1 mile from my house. A few months ago, I was shopping at Costco and decided to fill the car up with 92 octane from Costco. The funny thing is, for the next week or two I noticed the hesitation problem was 99 percent better and almost gone. So I decided to keep exclusively going to Costco for gas instead of BJ's to see if the problem goes away.

After running just Costco gas in the car for the past few months and with some very hot weather in Florida, I can confirm that the stumble and hesitation are completely gone. Just to confirm it, a few weeks ago I filled the car up with gas from BJ's and the problem returned. It wasn't as bad as before and I still had some Costco gas in the tank when I filled up at BJ's but I am sure if I filled up a second time with BJ's gas it would have been as bad as before.

At both stations I am using 92 or 93 octane ( I can't remember what the rating was at each place ) as they only sell two grades of gas, regular and super and I and filling up with super. I do know that Costco is tier 1 gas but when this problem started last summer, I only had 5K miles on the car and I put a bottle of Techron injector cleaner in the tank to be sure the injectors weren't dirty and causing the problem.

My advise is if you have this stumble and hesitation problem with you NX when it is very hot outside, try running a tank or two of gas from another gas station the has tier 1 gas. Run your tank down low before you fill up so you get as much "good gas" in your car as you can and see how it runs. I still can't believe that the gas was the problem and that is why I waited a few months to post this to confirm the problem was solved but I figured a national chain store like BJ's has good gas, my mistake.

I am back to loving my NX-350 100 percent now and very happy the problem is resolved!

 

I believe this is a software issue with the ECM and my NX350 turbo also does this. I only fill up with high quality 91 Ethanol-Free Premium from my local Mobil, which is pure gasoline. I don't think this is ambient temperature-related either. We had a couple of 100 + degree days last week and the one time I accelerated from a stop from a red light, I expected the car to hesitate, but there was no delay.

What I have found is this, from 0% throttle at a stop, if you roll or "tip into" the throttle, there is minimal or no hesitation. If you "stab" the throttle from a stop, like when you are trying to make a turn into traffic or something, the car will hesitate and not know what to do for a second before finally catching up and getting you moving. Very frustrating. I want instant throttle response from a stop on a EFI direct injected turbo motor like this.

Toyota Grand Highlander owners are already reporting the same issue with the T24A-FTS 2.4L Turbo motor that we share. They reported enough complaints to Toyota that they released a TSB about the issue, and a software reflash for the ECM that reportedly fixed the hesitation problem: https://www.toyotanation.com/threads...oblem.1773015/

If you scroll to the bottom of the thread above, you can read the TSB from Toyota. I feel us Lexus owners need to voice up and do the same, so hopefully they can release a software fix for us as well.

 

Can't really comment on your specific issue as I've never had hesitation from a complete stop myself, but just as an FYI the T24 engine in the Highlander uses different tuning parameters/software compared with the NX. The Highlander is detuned to produce less power and is compatible with regular fuel.

 

You are lucky if you have never experienced this. I read about this before taking delivery of mine, and sure enough over time I have experienced the same.

I'll give you an example that as one point in my life I was a delivery driver, driving a UPS truck sized delivery van. Our older vehicles were GM 4.8L V8 powered delivery vans. We received in newer generation trucks with Ford's 6.8L V10 powertrain. The first generation of these trucks were perfect with what what you would call the powertrain's calibration or "tune up". Instant raw torque and acceleration from that V10, and shift points were snappy from gear to gear. They were amazing, did what you needed to do when you wanted, and I had zero complaints.

A couple years later we received in a batch of newer trucks with the exact same body and powertrain physically, but I could tell there was a difference in a negative way. They made the "tune" extremely conservative..possibly to protect the transmission on such a large vehicle in a fleet service format? Huge hesitation and delay from a stop to the point of making it dangerous when you were trying to make a left turn across double lanes of traffic. You couldn't even get on the brake and give it a little throttle to "brake torque" it and get around the hesitation, there was too much protection built into the new PCM programming. It wouldn't let you regardless. The shifts were absolutely awful as well. Trying to jump on a freeway on ramp 2nd gear should be where most of the acceleration happens, yet they built in a ton of torque management delay and the engine would not come alive until it shifted into 3rd gear when it was too late..absolutely absurd.

My point in the above example is that manufacturers can take the same powertrain and build in more or less "protection" in the ECM calibration. Same is true for torque modulation for the transmission systems as I described above. The stock calibration with our vehicles is too conservative if you give it a quick stab from a stop. It freaks out and has to think about it for a second and hesitates. An aftermarket tune would fix this in a second but I would be happier to see the fix come from Lexus/Toyota, the same as we see in the TSB issued for the Grand Highlander vehicles.

 

Well, I guess it depends on exactly the issue. I don't experience engine hesitation or stumble (ie the engine having trouble getting proper power from sparking the fuel), but I have recognized that there is a safety delay in some situations stepping hard on the gas pedal, and yes, it can be annoying. I believe its due to the "sudden start restraint" system all to make sure Grandpa doesn't accidentally park his Lexus inside the mall again

 

.

Oh well, I pretty sure it would have worked. It worked great on a GSR.. Sometimes you need to treat turbos with TLC.

YMMV,
MidCow3