kiloken

Hi guys
As i am still learning about Lexus and need your advise. The problem appears only when pulling hard from cold start ie up hill, as the car warms after about a mile the problem goes away not to return until next cold start. The problem is an engine noise that sounds like a low note knock similar to a big end noise, it sounds to heavy to be tappets or piston slap. What I can not understand is if it was any of the above it would not go away as the car warmed. Revving the engine at a standstill from cold does not produce the noise, only under load.
Anybody had/have a similar problem?
The car is a 2006 GS300 with 133000miles on the clock
Cheers
Ken

Sodium

I've never had this problem or heard of it before, but the fact that it only happens under load, and not when revved at standstill (I'm assuming the car is in park or neutral), might suggest that it's coming from the drivetrain, as the drivetrain components don't move unless the car is in drive. Maybe try leaving the car on for 15 minutes before setting off to let the engine get to operating temperature, and then if you still get the noise under heavy load, this would strongly suggest that the source is somewhere in the drivetrain.

kiloken

Hi Sodium
Thanks for your reply, since I posted the original question I have changed the oil using OEM Toyota/Lexus oil, this seems to have cured the problem as since oil change I have not heard the noise. Worth a mention is that the old oil was in fact only in the car for 450miles having been changed by the garage selling the car, when I asked what oil they had used they quoted what it should be, not what they had used. I was suspicious and it looks like my suspicions were correct ,ie wrong oil used .
Cheers
Ken

Sodium

Yeah that makes sense, I can see how the wrong oil could do that until it's warmed up – they probably used something with a viscosity higher than 5W. Also, makes me wonder how they missed the directions clearly printed on the oil cap saying to only use 5W-30.

Well, I'm definitely glad that it wasn't a drivetrain issue, and also glad that you caught it as early as you did! Hope it's smooth sailing henceforth!

Gotcha350

And you should not be pulling hard on any modern engine when it's not up to temp...I don't baby any of my cars but you should let the engine reach optimum operating temp before beating on it.