Scott_in_Phoenix Posted October 6, 2002 Share Posted October 6, 2002 Hi there, I'm getting this weird "rattling" noise whenever I'm in a higher gear than is necessary and I press the pedal just a bit. It sometimes happens from a dead start but the surest way to get it to happen is to slow down to around 10 mph and then press the accelerator just a little in that "dead zone". It sounds like detonation but during my 60k tune up ( I have a 98 LS 400) the BMW mechanic swore it wasn't detonation. Of course, he didn't know what it WAS either. Ok, perhaps I shouldn't have gone to a shop that specializes in Beemers but they came highly recommended. Any ideas out there? Quote Link to comment Share on other sites More sharing options...
kulat Posted October 8, 2002 Share Posted October 8, 2002 check your engine mounts they may be loose. depending how loose they are they may rattle during torque at certain speeds. Quote Link to comment Share on other sites More sharing options...
Scott_in_Phoenix Posted October 9, 2002 Author Share Posted October 9, 2002 Thanks for the reply but I can tell it's not that... I was reading the Euro board and I'm beginning to think it's the oxygen sensors. Quote Link to comment Share on other sites More sharing options...
wolver1ne516 Posted December 20, 2003 Share Posted December 20, 2003 Are you sure it's not the valves clicking? I'm getti9ng that a lot when I'm easing off the gas slightly between 1000 2500 rpms in my 91 ls400. Thought it might be cheep gas but hasn't gone away for months. might need to go with timing belt n water pump change. Quote Link to comment Share on other sites More sharing options...
wwest Posted December 20, 2003 Share Posted December 20, 2003 In an airplane engine the most common cause of this is just one or two slightly or partially blocked fuel injectors. Oxygen sensor would normally detect too lean mixture but by the time the exhaust reaches it it's been "blended" with the other cylinder's exhaust. Quote Link to comment Share on other sites More sharing options...
jschunke Posted December 20, 2003 Share Posted December 20, 2003 Sure it's not an exhaust heat shield rattle? My 93 ls400 also had an engine related vibration at about 1700 rpm. Never did figure it out. Gave the car to dad and he doesn't notice it. So why bring it tio his attention. Quote Link to comment Share on other sites More sharing options...
jbatast Posted December 21, 2003 Share Posted December 21, 2003 Hey, I have the same problem and feal the vibration in the floor board and auto stick. Do you hear a clunk on start up as the motor turns back? I did not know that motor mount could be tightened? Quote Link to comment Share on other sites More sharing options...
bvorbau Posted December 23, 2003 Share Posted December 23, 2003 It may be transmission shudder. I had what seemed to be a similar problem, changed the trans filter and problem went away. Came back after about 60,000 miles, changed again, problem went away again. Quote Link to comment Share on other sites More sharing options...
K9crew Posted December 24, 2003 Share Posted December 24, 2003 Scott, I'm fairly sure that it's heat shield related since I have the same noise on my '99 and had the same noise on my '95 SC400. I haven't managed to crawl under the LS yet but when I looked under the SC I noticed one of the heat shield clamps was very loose. The nut and threads were badly corroded so I replaced the clamp with a 2" stainless steel hose clamp and the noise immediately went away. Your description is exactly what I'm now experiencing in my LS. I if go over a speed bump and accelerate slowly to about 10mph the noise is very obvious. It does it when the engine and exhaust are hot and not when cold which makes sense since the clamp expands when hot - obviously the exhaust expands as well but not as much as the clamp. :) Quote Link to comment Share on other sites More sharing options...
trd_power Posted July 17, 2004 Share Posted July 17, 2004 I haven't managed to crawl under the LS yet but when I looked under the SC I noticed one of the heat shield clamps was very loose. The nut and threads were badly corroded so I replaced the clamp with a 2" stainless steel hose clamp and the noise immediately went away. I don't own a lexus, this is for a friend but do you think you could send me of what the heat shield clamps look like? Or give me a link to some kind of diagram. I'm sure he'd be able to fix it but he has no idea what the head shield clamps are/look like. Any help would be much appreciated! Quote Link to comment Share on other sites More sharing options...
chips229 Posted July 17, 2004 Share Posted July 17, 2004 My series 1 has a sound also at around 17,1800 revs...to me it sound like its "pinking"....where the ignition is a little advanced.....i use normal unleaded...there is the dearer super unleaded here in the uk....im just waiting now until the low fuel light comes on.Then i will try a tank full of super unleaded to see if its the fuel as i think normal unleaded is 95 octane.I get the pinking under light throttle loading when the cars got into a high gear. Quote Link to comment Share on other sites More sharing options...
K9crew Posted July 18, 2004 Share Posted July 18, 2004 trd_power, here are a couple of photos that might help ... Heat shield before Heat shield after You can see the heat shields above the exhaust pipe. I replaced the clamps with stainless steel hose clamps many months ago and there have been no noises from under the car since that time. :) Quote Link to comment Share on other sites More sharing options...
.jpg.00b008f265e99d7d6120b5e549b3fd10.thumb.jpg.19472090d3f0c8af2c0ed917c349221d.jpg)
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.