Rough Idle at Startup

[Mindthegap]

Hi,

I picked up a used Lexus 450RX on Wednesday which is approved used.

It is a 2013 model with 66000 miles.

Both mornings when starting from cold there has been a judder and a slight knock for a few seconds and then settles down again. Have had a quick google and seems like this is not an uncommon problem. Some people reporting injectors being replaced, others saying it has happened for a couple of days after an oil change (Oil was changed the day before I picked the car up). Anyone any ideas on this?

Thanks

[Herbie]

It's never happened (yet) on my 2013 RX450h Advance (48k miles) so I can't help there but you'll get a better response if you post in the RX forum rather than the GS forum

[Mindthegap]

Just created a new thread under the right section! If there are any mods, feel free to delete this post 🙂

[royoftherovers]

59 minutes ago, Mindthegap said:

Hi,

I picked up a used Lexus 450RX on Wednesday which is approved used.

It is a 2013 model with 66000 miles.

Both mornings when starting from cold there has been a judder and a slight knock for a few seconds and then settles down again. Have had a quick google and seems like this is not an uncommon problem. Some people reporting injectors being replaced, others saying it has happened for a couple of days after an oil change (Oil was changed the day before I picked the car up). Anyone any ideas on this?

Thanks

Take it straight back to the Lexus Dealer you bought it from Jeff.

[johnatg]

Lexus V6 2.5 and 3.5 litre engines are prone to slight knock on start up (as are many other engines), caused by the hydraulic valve lifters sticking. That's caused by not-frequent-enough oil changes. Oil should be changed much more frequently than Lexus (and manufacturers generally) recommend in their service schedules - I'd recommend every 5K miles. And use an engine flush every time.

As long as it clears within a couple of seconds it's not particularly harmful - just irritating. But it may get worse over time and eventually cause problems so better to adopt a more frequent oil change regime - maybe do it yourself or engage an indie in between Lexus services if you'll be using the dealer.

[m4rkw]

1 hour ago, johnatg said:

Oil should be changed much more frequently than Lexus (and manufacturers generally) recommend in their service schedules - I'd recommend every 5K miles. And use an engine flush every time.

Doesn't the Lexus schedule recommend 5k changes anyway? I change mine at 3-4k depending on how it's been driven and *never* use a flush. Opinions differ on this but I've seen a few technicians with many years of experience recommending against putting anything in the engine except the manufacturer recommend spec oil. It's also apparently a good idea to try to stick to the same brand of oil if possible, as the additive packages differ between brands and changing between them can cause an engine to start burning oil.

Good info here on one highly experienced garage owner in the US on his opinion on engine (and other) flushes: http://www.agcoauto.com/content/news/p2_articleid/29

[m4rkw]

In fact some manufacturers have actually stated on the record "don't flush our engines".

[m4rkw]

Honda on engine flushes:

"Our engineers have conducted exhaustive tests to create specialized maintenance products and service standards that support the performance and longevity of Honda vehicles, and these standards don't include engine flushing."

GM: "Engine oil flushes are not recommended. If oil is changed on schedule, you shouldn't have to flush the engine."

source: https://auto.howstuffworks.com/5-benefits-of-an-engine-flush.htm

[johnatg]

Lexus service intervals are 10K miles for private owners and 12.5K miles for business users. What ????

Most Lexus models will be run by business users in their early years.

The thing with hydraulic valve lifters is that they have very small channels through which the oil is pumped. Now oil, even clean oil, starts to leave a thin deposit of gum on all internal engine surfaces from when it is first introduced into an engine - you can see it as a brown varnish-like film in a neglected engine, but it will be there, more or less, in every engine. It doesn't matter in most areas but if the hydraulic lifter channels get significant deposits they will have reduced flow capacity. It's still enough for the lifter to drain out when the engine is stood overnight but the restriction means that the oil doesn't get pumped in quickly enough to fully pressurize the lifter when the engine is started - it  can take a few seconds to fully pressurize. That means the valves don't open far enough, causing the misfire and rattle. (it's like a tappet with too wide a gap).

I have a Mk 1 MX-5 which has another engine prone to HVL gumming up - to the extent that Mazda abandoned hydraulic lifters for the Mk 2 and settled instead for solid tappets with shim adjustment - and a right pain they are. My MX-5 is nearly 28 years old - I have owned it for nearly 14 years and before me the first owner was a friend of mine and he had it for 14 years. It has had a flush for every oil change since new and is completely silent tappet-wise on start-up and has always been and it has suffered no ill-effects. It gets an oil change about every 3K miles. (It is supercharged too)

My IS250 kept its valve lifters silent for the 7+ years I owned it.

I have been changing oil in my, and various family members' cars for over 50 years and I've been using flush (various brands) for I would say the last 30 odd years - I have never seen any problem and no engine has suffered any failure in that time.

I understand why manufacturers try to dissuade owners from putting random stuff into their engines - but they will keep using hydraulic valve lifters.

That is quite an amusing article you reference and I agree with every word - except for engine flush for cars with hydraulic valve lifters. (Oh - and fuel injector flush - occasional use of a petrol additive to clean gum deposits out of injectors is beneficial)  And after all, engine flush only costs about £3.50 a time if you buy the flush several bottles at a time (My current supply is Comma Engine flush).

If an engine suffers from HVL rattle it can usually be silenced over a short period of time by changing the oil at say 2500 mile intervals, with flush of course

It's a controversial subject, but that's my twopenny worth! Your mileage may vary!

[Britprius]

Toyota/Lexus engines with VVT "variable valve timing" often suffer a rattling knocking at start up if the car has been stood for a couple of hours or more. More often than not this is due to the VVT mechanism draining of oil. At start up there is no oil in the hydraulic mechanism to hold the cam timing in a static setting. Once the oil fills the system the noise disappears.

John.

[johnatg]

Indeed - same reason though - the channels to the hydraulic actuator are very narrow - room to drain, but if they are gummed up (even slightly) it takes a few more engine revolutions to pressurise the actuator.

[Mindthegap]

Thanks for all the responses. Have spoken to my local dealer and they have booked the car in for an overnight so that they can test in the new year. Hopefully nothing wrong but would like it checked out all the same. Runs lovely after the initial startup so maybe all normal.

[Guest]

I recently mentioned all about the start up rattle on my 2014 RX450H and that Lexus had it back on three occasions to monitor.

The last time they kept it for a week but said the rattle didn’t occur when they checked it each morning.The problem is warranty won’t give them permission to do any work on it because there are no warning lights etc and the car runs perfectly well after the initial lumpy start or quick rattle.Personally I’ve stopped worrying about it as it’s all been recorded with Lexus on more than one occasion and it’s got warranty.

Bye the way I’ve had my RX450H for over 4 years and as far as I can remember it’s done this for at least 3 of them years.