bigDlexus

Anybody seen this one-

Occasionally, after my 99 LS400 (60k miles) has sit for a few days or more, I get a very stumbly start and a LOUD knocking from th engine. The knocking will last for about 1-2 minutes and then slowly go away to normal engine sound. I also get a heavy fuel smell from the exhuast that will go away after I get where I'm going.

The dealer is stumped by this one. I managed to video tape it so they can't just claim that they couldn't reproduce it. It's under warranty.

The dealer originally thought it was oil backflowing out of the heads and causing hydraulic lifters to act up. I wasn't sure about this but couldn't argue. I would think that engines this tight would have interfering valves and pistons.

After switching me to a lexus brand oil filter with a backlfow preventer, the problem still came back, indicating that was not the solution.

I think it's residual fuel pressure in the rail that is coming through a faulty injector and flooding out a cylinder. Is this possible? I am afraid that the noise is causing damage, but I have no choice unless I want to get towed every time it does it (once a month or less).

Any input would be helpful.. I think they are to the point of flying out some Japanese engineers to try and figure this one out.

Thanks in advance-

Big D

SharpLS-96

My guess was the same as your dealers, usually it's from using a poor oil filter with no "Anti-Drain Back Valve" and no "By-Bass Valve".

When you hear it knocking like that don't let it car run for a minute or two to warm up because you will do damage to the engine eventually. Immediately shut/turn the car off as soon as you hear it and wait a few seconds and then restart it, the knocking should be gone.

I have a couple of theories but first:
What type of gas are you using?
Is the car being driven for a very long period of time (several hrs) at a high speed of range (say 70-80 mph) prior to parking it for a few days?
Also, did you happen to switch over to synthetic oil and then the knocking started?

nthach

I also second the oil filter problem, check if your car has that dreaded orange can installed, it's a POS Fram filter!

What brand and weight of oil are you using?

bigDlexus

My post mentions that the Lexus DEALER installed oil filter didn't solve the problem. They put a filter on and the problem came back.

When it first happened, I shut it off a couple times and restarted and it still took time to go away. One time, I shut it off and went to get my video camera and came back- it still took the usual amount of time.

Gas type: NOTHING but super 93+ usually from reputable gas stations, althought that doesn't mean much these days.

Long drives: not really, maybe about an hour tops, (if that much) before parking in the garage.

Synthetic: I've never put synthetic in it. I don't race or push high rpm's repeatedly, so I don't need it. I just use 10w-30 in the winter and 10w-40 in the summer. (or is it the other way around?)

There are valid theories behind why it would be the oil filter, but if it could cause damage, and it makes this much noise, don't you think Lexus would make a bigger deal about the proper oil filter? You would think that a (very well) designed engine would REQUIRE a particular filter, and not just get occassionally upset when it doens't have the right one. PLUS- why would there be a very heavy smell of gas from the exhaust? The valve train shouldn't affect the spark plug firing. If gas is getting in, AND getting out, it should be there to get ignited, right? The only way it wouldn't fire is if the plug is fouled by liquid gas for a little while.

I'm not arguing with those of you that are way more knowledgable about these cars than I am, I'm just letting you know what has worked and not worked, and letting you know about some possibly valid theories.

ALSO- as a side note- the sound isn't knocking like detonation, it's more of a rapping noise. just FYI.

Thanks again for the input.

SharpLS-96

Are you the original owner?

bigDlexus

No, I've had it since 19k miles. It only started doing this in the last year or so.

SharpLS-96

Did your dealer or you reset the ECM to see if that helped? If not disconnect the battery and reconnect it to see if that makes a difference.
Another thing that comes to mind is that the VVTI (Variable Valve Timing Intelligence) mechanism might need replacing.

kevfeil

Did this problem get resolved? I have the same with my '98 LS400. If I let it sit for a few days it starts hard and makes a nasty noise when it does. Not for two minutes, maybe 10 seconds or less. It sounds like a fuel problem to me. I get the same smell from the exhaust, like it's been flooded. Just curious if the dealer figured it out yet. I'll keep searching for more issues like it.