azari

Hi guys,

This happened to me for the very first time yesterday on my '91 LS. The weather has been pretty chilly here for the past couple of weeks, dropping down into the 30's at night. I hadn't started the car at all for a couple days straight. I crank the engine, it starts, but very stumbly and struggling to stay on. In the mean time, there is a rather loud knock coming from the engine. There was I believe some smoke coming out of the exhaust initially as well. The car managed to stay on, and eventually the knock went away after a several minutes and the car ran normal. But it's very strange; what could this be??

BTW, I did do a search of the forum; but maybe I wasn't sure what to put in as the key word, so didn't come up with a whole lot.

Appreciate your help.

HKS_IS300

if you haven't started the car for a while the oil in the engine tends to settle and when you started it up it was just getting the oil all over the engine again. the smoke from the exhaust just might be the heat from the exhaust fumes since the weather is cold outside.

azari

Thanks for responding HKS,

I think if that were the case, many LS owners living in the colder climates would complain of that problem. And also, the smoke had a rather strong odor to it. But who knows...

GRAND_LS 4

iTrader: (2)

I edited the title... Please read the sticky:

https://www.clublexus.com/forums/sho...d.php?t=247695

mmarshall

The knock sounds like it could be piston slap, but that generally is not a problem with Lexus V8's. It is possible, however, if the pistons have worn to the point, in your 15-16-year-old engine, where there is a lot of clearance between the sides of the piston and the cylinder walls. The noise would gradually go away as oil pressure builds up and the piston expands with heat as the engine warms up.

The " smoke " and odor from the exhaust is probably water vapor mixed with sulpheric acid vapors.......more or less normal for a catalyst-equipped car. The catalyst works by converts the engine exhaust into water vapor with a slight amount of sulpheric vapor. If you haven't started the engine for several days, particularly in a humid climate like ours ( I am across the river in VA ), there will be a lot of moisture in the exhaust system, and it will turn to steam as the pipe heats up.

There could also be some real smoke as well if you have the worn piston condition I described above.....that would lead to some oil burning, and would generally be a bluish smoke.

91LS400vgb

I had this happen to me under the following circumstance: I started my 91 LS (everything normal) and backed it out of my garage, then shut it down immediately. About an hour later I started the car and returned it to the garage (again normal). Each time, the car was running for only a few seconds. Then, a couple of days later, when I started the car, I experienced something similar to what you describe. This was the only time it ever happened so I believe it was due to not allowing the car to warm up sufficiently those couple of times when the engine was obviously running with a rich fuel mixture (as it had not warmed up). The same thing once happened under similar circumstances to one of my other cars.