Jedidiah33

Hi guys,

I'm scratching my head on this one. I live in Canada, and own a 93 ls4.
I usually fill up on Shell 91 octane, but both times this has happened, I had filled up on another (both different) brand of 91.

I came out, started her, and got welcomed with a knocking. It sounds like a lighter engine knock, like a bearing knock only quieter/softer... so I panic and shut her off.

I jump out, check things out, and things seem proper (fluid levels, look leaks or damage etc) so I start again. If the knock persists, I shut off again and check again.

I've lost two other toyota motors (22r and a 3rz) from bearing knocks... so I am paranoid about them.

Both times (only happened twice) the LS400 starts with a knock, I kill it immediately. Start to troubleshoot and the knock disappears....
This time it was about 18c and had been raining all day. The car had been sitting all weekend.

So I go to find where the knock is coming from, and it quiets, I let the car warm up, and the knock is gone... a slight stutter every now and then that you can feel through the car. Stopping the brakes grind, starting there's a hesitation or miss upon acceleration. Go about 500 meters and the brakes clear up, the engine works proper and there's no hesitation.

Initially I fear oil... but it goes away....and I've only seen it twice now in 40k kms. The mileage is about 440k km, the valves(shims/adjustment) were redone about 50k-sih ago. The rest of the motor was good.

So then I start thinking, throttle body? Injectors? Coils?
I guess I really panicked about it because two weeks ago I lost heat inside the car.... and feared the worst... tracked it down to a kink in the heat control cable and mixing door linkage.
There was lots of white smoke(at 18c), and smelled rich. This went away when warmed up.

Usually, this car is a Sunday dream around town and can hold it's own on the highway in rush-hour when it needs to. Once it went for a little trip, it was back to normal.

I can't think of a way to troubleshoot this when it wont last more than 10 minutes... (which may be a blessing!)

Occasionally the car will sort of miss-start randomly... ie turn key, fire, noise, starter whirls. Noise isn't a backfire nor a screech... It's kind of a start'n'quit. Turn key again, and it starts after cranking for two seconds. Usually it is instant. If I remember right, the strange start only happens when warm started or it's been 'heat soaking', and even then it's rare.

The timing, and I believe water pump were done when the valves were.


Love the car, but don't understand what the quirks are pointing to.... any help is appreciated!

And just incase this is too much info, I'm most worried about what sounds 'like' a rod or bearing knock.