I have a Lexus LS500 2018 with 47k miles. It has two issues:
1) When engine is warm (if left for 45 minutes to 4 hours), it takes 3-4 seconds longer to start and some times I see some dark smoke from the exhaust for a bit. I have changed spark plugs and maintenance for the injectors but no change and mechanics gave up on this but it still bugs me.
2) I got check engine light two time. I have techstream so I could extract the data list at the time of misfire (it is cylinder misfire - cylinder 6 and 3). LT trim especially for bank 2 is a bit high and does not cycle (+7%). I have attached the full data list.

Last year, the car had a from end accident and had to replace radiator, condenser, fan, and air intake tank (it had a small crack). So I am thinking there is another leak somewhere that was not noticed but I am not sure that can be deduced by the data list. I would appreciate any comment as I have taken it to many mechanics but each is telling me replace something different without really having proper diagnosis behind their recommendations.

 

Who did the work after the accident? You have a warranty for the work done?
DId you own the car then?

 

I bought it with damages and it was repaired at an insurance approved workshop. The parts are all genuine but they may have missed something. No warranty.
One more thing, the check engine happened (both times) when I used remote start in a cold start.

 

I had a rear end Collison on my 18 LS500 in May. It was around 25k in damage. My car has been back to the warranty body shop 4 times for the same issue. It's been a week now with a independent mechanic. Waiting for the outcome.

If the repair was done by a insurance approved body shop, it might still have the body shop warranty. It might be worth looking into.

 

I take it you believe you have a coolant leak? Address that first. A miss on cold start tells me it's a fueling issue or fuel quality barring a coolant leak into 3 and 6.

ECU is dumping more fuel, thus the high fuel trim code. Did you use factory plugs?

Don't throw parts at it until you identify the coolant leak.

 

No, he believes he has a vacuum or intake leak. Air, not coolant.

 

You've got three fault codes. Did you google them to research what they mean?

 

Are you sure?

 

Thank you for taking the time to read and answer my post.
I have dropped the car back to the same shop hoping that they find the issue even though it didn't have a misfire again but it still takes time to start when it is warm.

 

Thank you for your answer. I believed it is a vacuum leak but I had that inspected extensively and nothing was found. So my hypothesis now that it is either some electrical issue; either ECU is compensating for something and putting in more fuel than needed or something is causing cylinder 6 not to spark on start up.

I use premium fuel, fuel pressure was checked and found within range, I replaced with factory plugs.

 

Thank you for posting. Yes, it is generic misfire code, cylinder 3 misfire, and cylinder 6 misfire.
when checking the misfire count; most misfires are on cylinder 6 and a few on cylinder 3. Other cylinders did not record any.
Weirdly, it has been 2 weeks and did not get any misfire codes again but it still takes long to start when engine is warm.

 

Thank you. I share your skepticism so I made sure that at least the big items are replaced with genuine parts. While they did a decent job on the body work, I do not think they did well on electronics because I keep getting issues with the radar. Now the radar is convinced I am driving in bad weather and keeps being unavailable. I left the car with the workshop, will see what they come up with.

 

You building this car back up after it was totaled?

 

Yes. It was not horribly damaged and the car is worth the pain.