kmd221

Yes I have always used premium gas in it. Especially now since having the issue the first time, I am making sure to run Exxon or Shell premium (just in case but probably over exaggerating!). I did get the car used about 1.5 years ago so I cant speak to what the other owner had done…

Could one bout of *accidental* bad gas really do this?

amberbs

I just had the same issue. It had to take with one of the heads on my engine had an incorrect air/fuel ratio. Mine only has 71,000. This would have been covered under power train warranty if it happened 1,000 miles before. It costs me $3,500 (Lexus paid half because I was so close to warranty and regular on service.). The dealership told me that it’s an issue they have seen a couple times with this car but not enough for Lexus to recall it. I think it’s unacceptable. Hope you have a better outcome. I am trading in my vehicle and switching to a different make.

kmd221

This is now the forth time the car is going to the shop in 4 months. Please see edits to my post for detailed timeline. Looking for advice- get rid of the car, or continue to work with Lexus?

AMTMJ

So are you still experiencing issues with starting the car or experiencing longer start times than normal? Are you still experiencing a rough idle and is the issue intermittent? What are the engine codes?

kmd221

Yes, still experiencing the issue with the car ignition not starting quickly. Also experiencing rough idle which is intermittent (occurring about 50% of the time). Engine codes previously have been “cylinder #__ misfire”. Different cylinders each time.

AMTMJ

are you getting any crankshaft or camshaft position sensor codes as well? Or just the misfire codes accompanied by the rough idle?

Also, does the issue with the lengthy start/crank time only occur after the car has been sitting for an extended period of time or does it occur regardless of whether the car is warm or cold?

kmd221

My service advisor has never mentioned the crankshaft or camshaft in communicating with me about the issues. They’ve only ever mentioned cylinder misfiring. Back in October, I did ask them if they found any issues with fuel injector, fuel pump or if they found issues with *any* of the sensors (was not specific) and they said no. I will ask that question specifically this time and confirm (waiting for a call back).

And, the car mostly has the issues turning over after sitting over night or in the cold weather.

AMTMJ

Then assuming you don’t have any crank or cam sensor related codes, then I would suspect an issue on the fuel system side (bad fuel has been ruled out). Are the misfires/engine light occurring in conjunction with the engine cranking/turnover delay you’re experiencing during a cold start?

Interestingly enough, another forum member recently posted an issue with long crank times that I responded to. I’ve attached a link below to the post. Read through the issue and my response completely, and see if it closely matches up with your issue. It’s not a common problem to have a faulty fuel regulator/check valve within the fuel pump, but I’ve seen it a handful of times on the Honda/Acura side, including on my own Acura TL-S. Toyota/Lexus uses a similar fuel regulator so it can certainly happen on these vehicles.

What tends to happen in these cases is the fuel pressure regulator check valve won’t completely seal when the engine shuts down and the fuel pressure bleeds down excessively. This causes longer crank times than normal typically after several hours of the car sitting, as the fuel system lines are not pre-pressurized and the fuel pump will take a few more seconds to build adequate pressure to the injectors. So it’s conceivable that the regulator is faulty, at least intermittently.

see link to post:
https://www.clublexus.com/forums/nx-...e-problem.html

miop4000

Thanks for your advice to my past post.

The car will switch off the moment it starts to crank.

Everything switches off. The steering wheel returns to its original position.

It’s been happening intermittently since the car was purchased and has spent many weeks in the dealership having everything tested.

Did it again yesterday. Very hard to replicate.

I suspect after 6 years of dealing with this that its an electrical problem not mechanical. Suspect its an immobiliser issue/security pairing issue.

The service manager I have known for-the last 11 years quietly said to me, ‘time for a new car’.

swiedom

Joined CL years ago when I had an IS but am back due to issues with my mom's car - was curious if her issue was a common failure and found your thread. Maybe not related but figured it was worth logging in and commenting...

Have they done a compression test? My mom's 2016 NX300 F Sport threw a CEL so she took it in. They found low compression on one of the cylinders and determined it was a bad intake valve. Apparently it is engine out to pull the head and replace. Yikes. Glad it is still under powertrain warranty.

2020nxbeauty

I have a cylinder compression issue so they are replacing the head. Under warranty

mochi230

My 2020 NX300, at 46k miles, was shaking, rpm bouncing when I stopped at a traffic light. People in the car can feel the strong knocking. The symptoms went away when I drove forward when the light turned green. I just brought the car to the dealership to check.