Engine Issue

[aahusman]

I just recently purchased a 1992 LS 400 with only 93,000 miles on it. A few days after I brought it home, I noticed that the car sporadically shudders when I am at a stop light for a minute or so. When I shift it into neutral, it stops. It seems to do it whether the A/C is on or off. I'm thinking bad motor mounts, but this I've never owned a Lexus or a V8 that is this old. I know that this car sat pretty regularly for the past 1-2 years, so it could be working some kinks out. I'm asking you experts out there, has anyone experienced this or does anyone know what it might be?

UPDATE: Ok, I noticed that when the engine shudders the RPMs drop by a couple hundred. It still only does it when I have the brake applied while in drive. Any ideas? Your help is much appreciated.

[landar]

I just recently purchased a 1992 LS 400 with only 93,000 miles on it. A few days after I brought it home, I noticed that the car sporadically shudders when I am at a stop light for a minute or so. When I shift it into neutral, it stops. It seems to do it whether the A/C is on or off. I'm thinking bad motor mounts, but this I've never owned a Lexus or a V8 that is this old. I know that this car sat pretty regularly for the past 1-2 years, so it could be working some kinks out. I'm asking you experts out there, has anyone experienced this or does anyone know what it might be?

It is very common for the transmission mount to go bad. And with the age of your car, the motor mounts might also be shot. The fact that you can shift into neutral and it stops could be several things. Maybe the tranny mount is bad or your engine is having trouble idling smoothly under a slight load... or both. The tranny mount is really easy to change so you might start there. With rubber parts, its more age-related than mileage so if yours have never been changed, its time. Your engine might also need a basic tune-up: plugs, wires, caps, rotors, etc.

[steve2006]

First thing is to check the engine idle speed when warm it should be around 650 RPM if lower it will cause problems like you have.

Common cause of low idle is the throttle body needs cleaning,also check all vacuum lines.