[NX 450h+] Cold start engine ticking/rattling noise

[Cicoria]

It happened two times already but I don't know when it started because I've been using my car in EV mode exclusively for the last month, however when I cold start the car in hybrid mode, during the heating cycle of the engine I hear a rattling/ticking noise which is "mechanical", it reminds me either of a belt or valve train,  however it comes from the side of the engine right about where the right wheel is.

I'm not 100% sure of the location because both times I didn't have time to open the bonnet and check, but I will do when I can and hopefully record the sound.

No errors from the dashboard or weir behavior from the car, it's just that noise and apparently it goes away when I drive.

What could it be? The car is 9 months old.

[HPS13]

Hi

If the car is only 9 months old, your car will still be covered under the manufacturers warranty? 

[Cicoria]

21 minutes ago, HPS13 said:

Hi

If the car is only 9 months old, your car will still be covered under the manufacturers warranty? 

Yes, of course it is, however since the dealership is 45 minutes away from where I live (all highway beyond the EV range) I asked here first because since it’s a cold start related phenomenon I wouldn’t be able to replicate it when I get there with warmed up engine.

I can try calling them and sending the audio when I record it when they’re opened during the week as soon as I can, but maybe it’s something normal and somebody here experienced it.

[Scotlex]

There are so many "things" under the bonnet other than the engine so it could be one of these "things" making a normal noise.

When parked up you could try starting the engine and open the bonnet and try to locate the noise.

As I said, it is probably a "normal" noise.

[Cicoria]

29 minutes ago, Scotlex said:

There are so many "things" under the bonnet other than the engine so it could be one of these "things" making a normal noise.

When parked up you could try starting the engine and open the bonnet and try to locate the noise.

As I said, it is probably a "normal" noise.

I tried blipping the accelerator to start the engine but the noise doesn’t appear, the engine runs smooth, probably it has to do with the rising engine rpm during the heating cycle. Is it even possible to accelerate the engine from P position like you would in a standard car in order to increase the rpm?

[stepppy]

I used to very occasionally get a similar noise when I had my Prius. From what I understand it was something to do with a brief delay in oil getting to the valve gear on the first start of the day. 

Not sure if this is what you have, but mine sounded like old fashioned tappet noise, but probably less than a second or two and as I say only probably happened three times in seven years. 

You could set open up your bonnet and have your phone recording then initiate the warm up process. 

The engine will only rev to a low amount when the car is in Park. 

[Cicoria]

@stepppy it definitely last longer than 1 second, for instance it happened at least after 2 minutes after turning the engine on and having driven up the garage ramp.

Maybe has this something to do with the imho excessive S4 heating cycle of the engine?

I recently tried a Corolla 1.8 a friend of mine bought and his cold start heating cycle lasted maybe 1-2 minutes in total then the engine turned off, just like my previous UX did with its 2.0 engine, but unlike my current NX which has a way lot longer cycle, it lasts several minutes and never understood why it took so long.

Well, as soon as I have an audio record I will update.

[Scotlex]

1 hour ago, Cicoria said:

@stepppy it definitely last longer than 1 second, for instance it happened at least after 2 minutes after turning the engine on and having driven up the garage ramp.

Maybe has this something to do with the imho excessive S4 heating cycle of the engine?

I recently tried a Corolla 1.8 a friend of mine bought and his cold start heating cycle lasted maybe 1-2 minutes in total then the engine turned off, just like my previous UX did with its 2.0 engine, but unlike my current NX which has a way lot longer cycle, it lasts several minutes and never understood why it took so long.

I am quite new to hybrids.

What do you mean by the S4 heating cycle?

[Cicoria]

21 minutes ago, Scotlex said:

I am quite new to hybrids.

What do you mean by the S4 heating cycle?

Sorry, my bad I meant S1 or stage 1 (of the heating cycle).

S1 is when the engine is cold and it’s what happens when you turn on the hybrid system the first time in the day, the car starts in EV mode and as soon as you push the selector to switch to HV mode the gasoline engine awakes. In this stage the power to move the wheels is drawn from the Battery at low speed while the engine heats and goes through all the remaining cycles —> S2 —> S3 until it reaches the fully operational hybrid level of S4, that means the system reached the desired operational temperature, which is also dependent on the Euro X compliance level of the engine. If I recall correctly for our cars it should be 65ºC and probably the bigger the engine, the slower the stages because there’s more to heat.

[Scotlex]

1 hour ago, Cicoria said:

Sorry, my bad I meant S1 or stage 1 (of the heating cycle).

S1 is when the engine is cold and it’s what happens when you turn on the hybrid system the first time in the day, the car starts in EV mode and as soon as you push the selector to switch to HV mode the gasoline engine awakes. In this stage the power to move the wheels is drawn from the battery at low speed while the engine heats and goes through all the remaining cycles —> S2 —> S3 until it reaches the fully operational hybrid level of S4, that means the system reached the desired operational temperature, which is also dependent on the Euro X compliance level of the engine. If I recall correctly for our cars it should be 65ºC and probably the bigger the engine, the slower the stages because there’s more to heat.

Thanks for that.

Is there any indication to show S1 to S4?

Every day is a school day 😀😀

[Notamech]

Check to see if your engine has D4S i.e direct and port injection. I had this on my is300h a while ago it sounded like a lifter tick on cold starts and lasted more than a few seconds and would not be present when the engine was warm. Was told that its normal and is because of the engine switching to direct injection under certain conditions. The noise was most likely the high pressure fuel pump or the injectors themselves. 

[stepppy]

9 hours ago, Cicoria said:

@stepppy it definitely last longer than 1 second, for instance it happened at least after 2 minutes after turning the engine on and having driven up the garage ramp.

Maybe has this something to do with the imho excessive S4 heating cycle of the engine?

I recently tried a Corolla 1.8 a friend of mine bought and his cold start heating cycle lasted maybe 1-2 minutes in total then the engine turned off, just like my previous UX did with its 2.0 engine, but unlike my current NX which has a way lot longer cycle, it lasts several minutes and never understood why it took so long.

Well, as soon as I have an audio record I will update.

I will be interested to see how long my warm up cycle is (non Plug-in version). in have not had the car long enough to note these kind of differences. 

My Prius was around two minutes even in the winter which always amazed me. Not sure if the NX has an exhaust heat exchanger like the Prius. 

Hope you get your answers soon. 

[Cicoria]

On 4/14/2024 at 7:42 PM, Notamech said:

Check to see if your engine has D4S i.e direct and port injection. 

Thank you for the reply and, yes, all the engines from the dynamic force family have D4S.

I tried recording the engine today but the noise didn’t appear, so I wasn’t lucky.

23 hours ago, stepppy said:

I will be interested to see how long my warm up cycle is (non Plug-in version). in have not had the car long enough to note these kind of differences. 

My Prius was around two minutes even in the winter which always amazed me. Not sure if the NX has an exhaust heat exchanger like the Prius. 

Hope you get your answers soon. 

I didn’t clock it too, however today I turned the car on and listened for 2-3 minutes to no avail, all was normal, then I drove for a very little distance before stopping (1.6 km) and according to Lexus Link I drove for 50% of the distance in EV and the remaining distance on petrol for a whopping consumption of 16,1 L/100 km. 🫣

Since this small travel lasted in total 10 minutes, I estimate that the heating cycle before the petrol engine could be able to shut off was circa 5 minutes or so.

I had other hybrid Lexus cars but this NX fires the engine on a lot of time even if I drive it for 20-30 km and park it for less than an hour, when I get back to drive home the engine turns on even if the heat outside is hot like today while other hybrids always stayed in EV. 

It could be interesting to see indeed if this behaviour is something related to the plug-in system or if it has something to do with this engine. The Battery was 98% today, so it could assist at any time.

[SA1]

I have found that if the engine cuts in from EV mode, for the initial cycle it is very noisy with a ticking, knocking noise.  If I start it in HV straight away generally it is quiet from the start

the other day I happened to start it with the accelerator depressed and the noise was there. 
 

i find that the engine will cut in on EV mode even with some miles of range left when the temperature is below 15 deg and often it is as I am accelerating (even gently) and so it could be that if the engine cold starts with the throttle open something else is happening

to me it sounds like something ancillary to the engine (AC etc) or something is loose when cold, as once the EV goes back on any subsequent engine running is ok

i will mention it to the garage when I’m in next time but I won’t hold much hope

[Cicoria]

10 hours ago, SA1 said:

i will mention it to the garage when I’m in next time but I won’t hold much hope

Yes, I will too because next week I'm going there to swap the wheels with the summer tires but I have zero hopes because every time I ask something technical to the mechanics, all they say is "if there are no errors after the ECU scan, then the car is fine".

Things like these make me happy that I lease every modern car since years. If issues should arise after the warranty is expired, that won't be a problem of mine.

[Cicoria]

Update: Of course since I started monitoring the engine, the sound never happened again, even today that the temperature were very cold, so I asked the mechanic chief when he was servicing my car and he told me that it could be something related to the injection in the heating phase because I told him that it's a temporary sound and not always present especially when the engine is under load, however there are no errors per ECU scan and he told me to monitor the car regardless even though everything should be ok.

[JohnLexus]

I believe this engineer explains exactly why the noise happens at exactly 15:00 minutes in his video : 

 

https://www.youtube.com/watch?v=9GWKBbEMCC4