Uneven idle (not rough)

[YarisHybrid2016]

Hi,

I think I'm getting paranoid.

Car cold started last night on level ground. Left idling through warm-up with heater on 18 deg. C (so not immediately driven for maybe 10 mins while I messed with satnav).

At one point, RPM increased to a higher steady RPM for maybe 3 secs, then back to idle for 3 secs, then back to the higher RPM, then back to idle.

I wasn't anywhere near the throttle, and there was a change in engine sound when this occurred.

My guess is the car was momentarily uncertain of what it wanted to do, and the EGR valve moved during this time.

I don't recalll it doing this before which is why it caught my attention.

It's rocketing towards 100k miles, and part of me is contemplating getting the 100k service done early (as I understand it, there are some extra items done at this time).

I'm also unsure if the timing chain is starting to get noisy. Is this a thing on the 1NZ-FXE at this milage?

[TonyHSD]

Hi, 

I have no experience with Yaris hybrid engine but I believe that they are similarly designed to bigger 1.8 hybrids this what you have experienced might count as normal.
Happens because the engine been loaded to recharge the Battery, then unloaded and just idling to warm up itself , then Battery been fully charged and engine is again loaded but slightly different to discharge the Battery. These cycles will repeat again and again, but to find out you need to keep the car in ready mode for longer without driving. I do that often, sometimes for hours. 
If the changes between engine load are very pronounced it might be as a result of dirty egr and throttle body plate that got sticky. At this mileage it will be a good idea to give them a clean. 

In 1.8 hybrids 2zr-fxe engines when those gets dirty there are also loud knocking sounds on cold starts and vibrations at around 40mph and 60mph or when the engine is at low load near tick over 1000-1400rpm and steady motorway speeds. 

[YarisHybrid2016]

I'm reading that at 100k+ miles they start burning oil, the lower oil seals start leaking, and the timing chain stretches necessitating replacement.

Mine is NOT burning oil, 6 months later the oil is still golden in appearance (approx. 5000 miles), except for what appeared to be chain noise.

I haven't noticed unusual vibration.

I'm just aware that in the next 8 months I'll put another 15k miles on it (70/30 motorway/city), and quite a few places are suggesting 100-150k miles is the lifespan of this engine. I'm considering though that many of these cars probably only do short trips in the city. I don't see many Yaris on the motorway, relatively (I see from most to least, Corrola, C-HR, Rav 4, and Cross), and even the gen. 4 Yaris isn't that common.

Mine rarely does short trips, and when it does, it's usually on the back of a much longer one, so rarely runs cold anywhere.

It's not exactly a case of preventative maintenance, either, as cylinder wear is down to "how you treated in the past". I ran it in when new, serviced it to schedule (I did a few extra oil/filter changes on it, too, including at the first 1000 miles of its life), and don't go WOT when cold.

I just hope it remains well for the next 8 months. 😄 I'm going to miss it for sure.

[YarisHybrid2016]

On 4/20/2023 at 7:28 AM, TonyHSD said:

These cycles will repeat again and again, but to find out you need to keep the car in ready mode for longer without driving. I do that often, sometimes for hours. 

If I'm going to idle from cold, it's usually because it's cold and I'm running the heater to demist. Max. 15 minutes before I'm driving.

I'm aware of the different sounds it makes, but this seemed different from the usual. I'll keep an "ear" on it and see what happens.