LS 0181158

I changed out my 1998 LS 400's faded gold-plated emblems/badging for chrome last summer. Since then, I have been meaning to (but never actually did) replace the gold "L" emblems on the wheels' center caps. Stock 16" 5-spoke polished/machine-finished alloy wheels--you know, the standard wheels for a 1998-2000, with the center caps being slightly "recessed" as opposed to the "flat" caps on a 1990-1997 LS. It's not been super-critical (obviously), but my car looks kind of dumb with all chrome badging except for faded gold logos on the wheels. I submitted an inquiry to www.junkyarddog.com to see if any junkyards could provide 4 replacement caps with chrome "L" emblems. However, if they don't come through, does anyone know where I can get just the chrome "L" emblems themselves? How are they attached? Are they just glued onto the center caps? I checked Lextasy and Lextreme, and while they sell the badging I already replaced, there is nothing for the wheels. I'm trying to avoid buying four OEM center caps with chrome logos brand new ($200 or more, I'm sure?), but would be happy to spend $60 or less for a different solution. Any ideas? One reason I like the idea of changing out the emblems only is that I wouldn't have to worry about new center caps not necessarily matching the 11-year old finish of my machined wheels.

SKperformance, interesting what you said about the alignment. Could be possible; I definitely should get that checked soon, because I don't want my new tires wearing poorly. You said you had the dealer "add pressure?" Only one other person (aside from valets, etc.) has ever driven my car since I bought it, and I was in the car with him when he drove it. I don't have any kids :D . Personally, I drive VERY conscientiously and take care to avoid any kind of road imperfection, including potholes and utilities. Roads are pretty smooth where I live, and my rims are the standard 16" 5-spoke ones for a 1998 model. Haven't hit anything major I can recall recently, and certainly no curbs :o . I suppose I'll find out in about three weeks if a rim is indeed bent (when I get the new tires put on). At any rate, everything should be perfectly balanced right after the tires go on. Marklouis, transmission mount? That's an interesting point. I can't emphasize enough how faint the sound I'm talking about it--I mean, it's really just "barely there." But if it persists after I get all the work done (I have a nagging suspicion it will), that'll be one of the items I check. Thanks!

Hmmm... Thanks to all who responded! I mentioned those other issues in my 3rd paragraph [Car is a 1998 LS 400...] just so people would have some background on the condition of my car at this time, but not because I thought the sound and those issues were directly related. I will get my tires and brakes replaced next month--just trying to set a date with the mechanic--so of course I'll be delighted if by happenstance these new parts do away with the problem (which like I said began occurring suddenly less than a week ago). Bali26, my brake rotors are definitely warped (steering wheel shake upon brake application), but they're being replaced with these rotors [http://brakeperformance.com/site/brake_rotors.php?ad=google&gclid=CL6Z0Y_L9pgCFQsMGgod8G6ykg] and these new pads [http://www.ceramicool.com/] next month. I already have the parts. There haven't been any symptoms of dragging (no pulling to one side, worse gas mileage, etc.), and I think if one was dragging somehow, the pitch of the sound would change. Nevertheless, my brakes are being completely replaced next month, so if they were the source of the problem, it should be eliminated. amcdonal86, strut rod bushings? I will make note of that. If the vibration persists after I get new tires, I'll have those checked first. curiousB, you know I actually considered wheel bearings already after someone speculated they may be a source of the vibrations (if not the tires). Note the noise I'm talking about, though steady, is VERY faint. I don't know what worn wheel bearings sound like, but there is no squeaking, scratching, grinding or other irregularity in the sound I'm hearing. You also mention tire balance (or lack thereof) and broken cords. I first noticed the vibration (clearly unrelated to my new humming sound) sometime last summer. It prompted me to of course check tire pressures and (when that made no difference) get all four tires balanced--this was 7/2008. Although I didn't ask them to do it, the tire place also rotated my tires at the same time. The slight vibration wasn't affected at all by this, so either they didn't balance the tires properly, or this was not the issue to begin with. Later that fall, a coworker suggested "cupping" might be the source, but at any rate the problem didn't get any worse until about a month ago. Now the slight vibrations in the steering wheel and chassis (always most prevalent between 75-85 mph, my favorite cruising speed) are actually VISIBLE as a subtle, rapid, side-to-side shimmy in the steering wheel at speed. At the same time, I've been noticing pavement seams, expansion joints and things like manhole covers register more sharply through the suspension, but bigger stuff is absorbed smoothly as always. I'm guessing and hoping these various irritating symptoms will be eliminated with fresh rubber (planning on Yokohama ADVAN S.4. V-rated all seasons) next month. Current tires are Dunlop SP Sport 5000, which I believe were OE. I drove a '95 BMW 525i with badly worn ball joints for a month several years ago. You could hear a prominent whine from the front end anytime the car was in motion, but its pitch changed faithfully in relation to road speed. I swear to you the hum I'm talking about doesn't change pitch or volume at all. I haven't driven my car much over 80 mph since the noise started, but all characteristics of the sound are identical whether speed is 35 or 80. It simply doesn't exist at less than 25 mph. Except for the odd "tapering off" I described in my first post (which happens briefly over a <5 mph reduction at relatively specific speed), the hum vanishes all at once as the car slows and likewise appears abruptly during acceleration. You could drive all day at less than 35 mph and never hear it (since you have to travel at least that fast for it to START humming). SKperformance, maybe it is the tires, but not an alignment issue--I'm quite sure of that. MD state inspection (admittedly done at 118K) showed PERFECT alignment, and aside from the slight vibration I've talked about, none of the driving characteristics have changed. Steering wheel is dead centered when traveling straight, and there's no pull to either side at any speed. Perhaps I should just stop complaining and be patient until tires and brakes are replaced--only about four weeks to go anyway. The nature of the sound just can't convince me it's related, though. curiousB, I think your resonance theory sounds most likely, but...I don't know from where. I guess we'll see eventually. I'm sure the new tires will be quieter than my worn Dunlops--so I'll be able to hear the hum even better then.

Sorry to disappoint right off the bat, but this is not a post about my car's musical talents. I will be extremely surprised if ANYONE can solve this...sort of riddle...but figured running it past you all couldn't hurt. It isn't a big deal, but the issue bugs me and will continue to do so even if it DOESN'T get worse. Car is a 1998 LS 400 with 152K. Most recent oil change was 500 miles ago (changed every 3,000 religiously). At 130K tune-up, I was told the throttle body was very dirty and the fuel filter should be replaced. I haven't tended to either of these items, but plan to get both addressed at the end of March at the same time I have new tires and new brake rotors/pads installed. My tires are pretty well worn, and I think the ride is suffering. The car doesn't ride as smoothly as when I bought it with 115K; small imperfections in the road come through a lot more harshly. There are also small vibrations shaking the chassis and steering wheel (especially at 70-85 mph), and these have grown gradually since last summer. Late last week, I noticed a very, very subtle humming, manifested only under certain conditions. Let me describe the sound: It is honestly most similar to the humming you might hear in your head once in a while--kind of a "phantom noise" like one's ears ringing--you're very conscious of the sound in your own head, but it doesn't actually exist and certainly isn't audible to anyone else. Initially, I thought I might be imagining the sound, but realized right away some aspect of the car itself is generating this medium-pitched hum. The closest mechanical equivalent of the sound I suppose would be the whir/hum of a fuel pump, or something of the like--but in my car the sound is a bit more subtle and doesn't seem to be coming from any specific location that I can tell. You can't hear it outside the car to my knowledge, but it'd be hard to be sure since the noise only manifests at speed. When it occurs, the sound is persistent and steady, but again not very loud. At highway speeds it's not as noticeable due to greater wind and road noise--however it is still audible and remains absolutely constant. Now, about WHEN the sound happens: *Starts consistently when speed exceeds 35 mph. Has begun as low as 25, or as high as 40. *Consistent volume and pitch at ANY speed once the sound begins, until speed drops back below 25-30 mph. Then it disappears. *The pitch DOES NOT change with vehicle speed, throttle position or revs. Neither does the volume. This is why it reminds me of a fuel pump--the sound is ever-present UNLESS the car is traveling less than 25-30 mph. *The only variation in pitch at all is right before it goes away (as speed decreases through 25-30 mph). It kind of "thins out" and the pitch rises SLIGHTLY before the hum disappears suddenly and completely. *I can't make the sound happen unless the car is in motion above the speed range I referenced. I tried revving the engine to 2500 rpm in Park--no hum. Plus, it has nothing to do with throttle position. Even if I jump on the accelerator hard from a stop, there is no hum until the car exceeds 25-30--the same as if I had gradually coasted up to that speed range. *I can't make the sound go away if the car is in motion above the speed range referenced. I have put the car in neutral at 35-40 mph and let the revs drop to idle. The sound remains consistent in pitch and volume (until speed drops below 25-30 of course, when it abruptly vanishes). *Generally, the hum starts at a higher vehicle speed than it stops. For example, it might start as I accelerate through 40, but continue on until my speed drops back through 25. I have ruled out: TIRES. I know mine are worn, but you can imagine that by now I'm well aware of what my car's tire roar sounds like at different speeds. Plus, the pitch and volume of generic road noise always varies with speed. This particular hum stays exactly the same, regardless of whether I'm going 45, 60 or 80, and regardless of the road surface. WIND NOISE. I have owned the car since 115K. Its aerodynamics clearly haven't changed at all. FUEL PUMP. I've been in cars with noisy fuel pumps. The pump's noise was always present, especially noticeable at idle when other environment sounds are least intrusive. As I've said, my humming sound ONLY shows up above specific road speeds, and is quieter than a noisy fuel pump. I'm not sure it's loud enough that a passenger unfamiliar with my car would even notice (plus any LS model is more silent than the vehicles most people are accustomed to anyway). DIFFERENTIAL OR OTHER TRANSMISSION-RELATED. Differential and transmission fluid were both changed at 130K. Gear noise [i think] would change pitch with road/engine speed. The hum I'm talking about maintains the same pitch even if I downshift manually to lower gears. But the sound is NEW, and that's why it bothers me... Sorry for the long, long description--but any hypotheses would be much appreciated!

Interesting. That article makes sense.

I remember reading on a Mercedes forum that OIL temperature is more important than COOLANT temperature when it comes to putting stress on the engine--and it takes longer for the oil to warm than the coolant. All older Mercedes' have an oil pressure needle with "1," "2," and "3" marks. When the car is cold, the needle stays at "3" (highest level) even when the car is idling. As the oil warms (becomes less viscous, I suppose), the needle settles down during idle, and its movements become directly sensitive to throttle inputs. This happens somewhat after the coolant temp needle has reached its operating range. I recall someone on that board saying that only after the oil warmed up (evidenced indirectly by the pressure gauge) was it fine to drive the car "more aggressively." A baseline I've established on my LS 400 is to wait until the climate control fan kicks on (first bar shows on the display). When it's warm out, or the car has just been driven, the fan operates immediately. However, when the car has been sitting overnight and it's colder than, say, 50 degrees, it can take 2-3 minutes for that first bar to show up. Either way, it allows time for the RPM to settle down from the initial 1200 rpm idle, and the transmission doesn't act as stiff as if I were to begin driving the car immediately. Fortunately, my 30-35 minute commute initially involves low-speed (40 mph) driving in top gear--low rpm--before I get on the highway (75-80 mph) for the final 15 minutes.

AM only, wow that sucks! One of the reasons I'm hesitant to do this is because the dash is put together so snug and the car overall so tightly built (even at 133K) that I'm afraid that the dash will never be quite as tight after I pull it apart. But as more bulbs burn out, I guess I'll become so annoyed that I'll end up doing it myself--or getting the work done somehow. I meant to ask you earlier--what do you think of the Nakamichi sound in your LS? It seems to be a relatively rare option. I've driven two '93's, a '90, a '95 and of course my '98, and they all had the standard [Pioneer-derived] system. Sounds excellent IMHO...I think the best in ANY car I've driven. I can only imagine what the Nakamichi must sound like. My future budget is limiting me to a 528i 5-speed or 540i 6-speed, but I have desperately wanted an E39 M5 ever since those came out. Now they are becoming "affordable," but $25-30K is still out of my price range, especially for a second car. I prefer the control of a manual, especially if I already have a big automatic sedan to commute and take long trips in. And eventually I'd like to replace my LS with an '04+ LS 430 or [i'm starting to think] an '04+ Audi A8...but that will probably not be as reliable (will anything?) You have clearly driven more and nicer cars than I have. From what I have heard and read, the newest BMW's (including the 550i) are dynamically superior even to BMW's fantastic earlier models--and anything else on the road. I just dislike the styling of the 5-Series from '04 on and 7-Series from '02 on (although the upcoming '09 or '10 7 looks much better!) I prefer the contemporary styling of Audi, Lexus and the more high-end Mercedes models, and thus am probably more likely to buy one of those in future years, I guess. But it seems like the engineers at BMW recognize what the joy of driving is all about, while other manufacturers merely try to add "sport" to their cars.

OK, thank you very much! I checked out that tutorial, but the pictures and descriptions relate to a 1990-1994 LS 400. In 1995, they changed the dash layout and in 1998 yet again. My 1998 has the clock/temperature display BELOW the vents, with a wood trim strip separating that display from the climate control display below. Also the lower console strip is ONE wood piece (as in your 1996), rather than a lower console wood and separate ashtray as part of the dash. I'm still kinda scared to try... But I'll bet I could take the climate control unit out once it is somehow removed from the dash. Did you imply you already did this with your LS? I like that you have a 1997 740iL also. I drove a Mojave Brown 1997 for about 10K miles--a superior car to the LS 400 in terms of pickup, handling and driving feel, despite its larger size all around. Plus I really miss those neat LED spotlights for the ambient interior lighting at night. At some point I'd like to get a 1998-2000 528i or 540i 6-speed as a second car. I've already owned two older 5-Series previously.

I have continued to lose night backlighting for various buttons in my 1998 LS 400's climate control display (non-navigation)--notably all those above the LCD display, the driver's TEMP adjustment button, and a couple below the LCD display. ALSO, the backlighting for the passenger's-side heated seat button and VSC button (both located in the lower wood console) is also gone. I have read some of the board discussion about part numbers and purchase options for the bulbs themselves--however, I'm curious how difficult it would be to remove the climate control unit from the dash and gain access to the bulbs; if it's something a person of average intelligence and patience can do himself, what are the steps involved? And how about getting to the bulbs behind the heated seat and VSC buttons? Any advice or redirection would be appreciated! Thanks.

Thank you both of you for your replies. I will definitely look in to these options. I guess it looks like Bluetooth is probably the way to go...

My 1998 LS 400 has the built-in handsfree design for the Lexus Portable Plus cellular phone (wiring, buttons/mic on the steering wheel). The antiquated but original Portable Plus phone still resides in its dock in the upper center console. It's plugged in to the original curly IVM cord, and beeps a greeting through the stereo speakers each time the car is started. Of course, the service for this phone is no longer active, and it would be pointless to attempt to reactive the original outdated and bulky handset for a variety of obvious reasons. I'm not a fan of walking around with a Bluetooth device on my ear (and don't have a Bluetooth-capable personal cell phone yet), but I'd really, really like to take advantage of the in-car handsfree system for my personal phone. Currently my service is with Sprint and I have a Sanyo MM-7400 handset, although I plan to upgrade to a secondhand Sanyo Katana II in the very near future. Do any of you have suggestions or recommendations for how (if possible at all) to hook up and dock my intended new Sprint handset in the center console location as elegantly as possible so I can utilize the car's handsfree capabilities/buttons on the steering wheel? In my utopian vision, I would simply go down to the Lexus dealer and purchase a cradle and new curly IVM cord matched with the Sanyo Katanna II (or other modern Sprint phone if necessary), pay my (big?) money for these items, and be done with it. Simple plug and play. But I'm sure it's not that simple! I'm sure some of you have gone through this already--wanting to use contemporary cell phones in older Lexus cars. As a matter of fact, given how quickly cell phones become outdated, I'd assume Lexus had a solution for the new-car buyer who planned to keep his Lexus longer than his cell phone, yet still wanted the convenience of the handsfree system!

OK, thanks very much! I will try to schedule a time at the local Toyota dealership, and make sure they use the fluid you specified--and DRAIN and refill the fluid rather than flush it. Penzoil wanted $110 for the service--I imagine the Toyota dealer would be a little more? I checked out the tutorial, and it doesn't look that hard. I just don't have the place or adequate tools to do this, and I'd feel more comfortable having a "professional" do this, although I'm sure I agree with most that no one can really be trusted regardless of where you go. Would you say I'd be good for another 30,000 miles after getting this done? The manual also indicates changing the brake fluid, coolant and spark plugs at 120K, asl well as having lots and lots of other stuff inspected. Any recommendations with regard to this? I'm more likely to get this maintenance done piecemeal rather than paying for it all at once--but regardless, I'll try to address the other fluids and spark plugs ASAP.

My 1998 LS 400 has between 120-121K miles on it now, and I had planned to address a transmission fluid change--which I understand is to be done every 30,000 miles. When I brought the car to the local Penzoil shop for an oil change 1K miles ago, the tech advised me that the automatic transmission fluid was quite dirty and recommended FLUSHING and replacing the transmission fluid. I've only had the car since 116K, so I am not intimately familiar with either its past maintenance history or specific procedures necessary for service. But I want to take as perfect care of the car as possible, as it's in near-flawless condition cosmetically AND mechanically. My questions are as follows: 1. Allow them to FLUSH the fluid, or DRAIN and replace only? I have heard that flushing can generally be damaging to the transmission, although draining will not allow as much fluid to be replaced unless it's done repeatedly in short order. 2. Should I specify only a certain type of fluid be used as replacement? I know the Owner's Manual will advise the generic TYPE of fluid, but do you feel it's actually worth purchasing a specific BRAND from the Lexus dealer or auto parts store? For instance, I know that the coolant should be the red Toyota kind, and not the generic green variety--so I was wondering if a similar rule applies for the automatic transmission fluid? 3. My 1998 UCF20 has the 5-speed automatic, vs. the 1995-1997 models with only the 4-speed. Should any special attention be paid as a result of this fact? 4. Finally, do you feel it's a bad idea to ask a place like the Penzoil shop to perform this service on my car? I'm not someone who would typically jack up the car and do this myself, but I also see no reason to pay the Lexus dealership big $$$ to do a relatively simple service such as this. Any thoughts? Thanks very much for any wisdom you can offer!

Thanks 93ls400walt; I will try your suggestions if I get a chance. I really am beginning to lean toward a bad ECU, though, because these symptoms are not present consistently--there's no consistent, reliable rough idle, no loss of power under certain repeatable driving conditions--the car is either perfect or it is acting up on a spectacular level. The problems I described are very alarming and don't "develop" over any time period--they appear like snapping your fingers, and may go away just as quickly. Sometimes they don't occur at all, for quite a while. I would say this is definitely an electrical problem--computer, wiring, connections, something like that; not a mechanical, wear or dirt accumulation issue because as I said, the car would behave shoddy all the time if it were. Thanks for your suggestions though. I will definitely check those things if I get a tuneup done.

Well, the problem is fixed. Not water pump, but FAN BRACKET. Check engine light problem is back, though--please see my new thread ("How to remove ECU") here if you have ideas.

I am still having check engine light problems with my 1993 LS 400. After an extended sit, car is normal for the first 15-20 mins., then the CEL with rapidly flash on and off and the car will jerk violently in time with the flashing, alternately losing and regaining power many times per second. This makes it impossible to attain more that 40-45 mph on the highway. The light does not stay on consistently for the most part, but flashes on and off rapidly. Sometimes the problems goes away for a few minutes, only to return later. As I mentioned earlier, the car runs VERY RICH when this happens, blackening the back bumper and burning through gas at a mind-blowing rate. At most recent visit, Lexus dealer pointed me toward a bad ECU ($1500). I don't know if this was just to get me to leave, but on the previous visit they suspected the MAF sensor, which I replaced. On this second visit, they claimed the car was not throwing any codes and condemned the ECU as a result. Does this indeed sound like an ECU issue? I found a place online that claims they will rebuild your '92-'95 Lexus ECU for $265, although they will not charge you anything if there is nothing wrong with it or it is unrebuildable. However, I've also heard of ECU's being picked up at junkyards for $150. Am I barking up the wrong tree here? If not, where is the ECU located in my 1993 LS 400 and how do I get it out? Any precautions besides disconnecting the battery and avoiding static discharge?

By the way, nc211, thanks for that tip about www.lexuspartsonline.com. It is a great site. I've already checked--serpentine belt, $36, idler pulley, $50, tensioner, $144. I'm 22 and since 17 I've owned an '86 BMW 528e w/250K and rebuilt engine just before I got it (drove it 40K), '90 Acura Legend LS from 150K to 201K, and '90 BMW 535i 128K to 175K. I do understand what you are saying about a few hundred $ here, few hundred there, etc. I've had to do $500-700 services on all those cars at one point or another, plus those many smaller services and realize this is normal and expected. I'm a little disappointed to be having all these problems with my LS so soon, but I know the car is not really to blame and your point is well taken. I'm more frustrated that I'm right now in a bad way financially and can't take care of these problems as immediately and properly as I'd like. Still, I must disagree with your one comment--I've finally driven my long-coveted Lexus LS 400 and know this is definitely the right car for me! :-) I just might have picked the wrong time to get it. Any ideas about my above post are so appreciated--sorry for the length.

Okay, I have some further developments. The car is continuing to do this vibration thing, but now it does it a bit more across the rpm range, and the primary vibration has moved up from 1000 rpm to about 1200-1300. It is now making a pretty disturbing racket, primarily at idle or low engine speeds. At idle, I hear a very rythmic, high-pitched and somewhat metallic "squeak-squeak-squeak" sound, which goes away as soon as rpms are raised. There are also occasional and COMPLETELY RANDOM "click-clack-clunk" sounds, and frequent, lower pitched and very bad-sounding metal-on-metal grinding, which is rythmic in nature but seems to come and go at will, regardless of exact rpm...i.e. the car can be idling, the grinding will continue for 10 seconds, then there will be a "scritch-scritch-scratch" sound and the grinding will disappear, only to return 25 sec. later. Sometimes, sitting in the car at a light, I can even FEEL knocking through the chassis as these "clunks" come and go. All this noise seems to be coming from the very front of the engine. Tonight I opened the hood with the engine running and discovered that the serpentine (drive) belt appears frayed in several places on the edges, and is riding up on the edges of at least the top two pulleys. There are NO WARNING LIGHTS on, the power steering has always worked perfectly, there are no apparent alternator-related problems (lights dimming, accessories running more slowly, etc.), the car has never stalled or lost power under these conditions, transmission shifts fine, and coolant temp remains at its a-bit-less-than-halfway mark. Climate control on or off makes no difference, except to kick the revs a bit up or down like normal. No leaks, either from power steering pump or water pump. The car seems to have normal power and is eminently driveable at freeway speeds, although the racket can still be heard at a very muted level. The engine itself still purrs and revs very smoothly. I just changed the oil yesterday, but have no records as to when the timing belt or water pump were last changed. Regular service procedure would have mandated this being done 26K miles ago, at 180K. I'm hoping this service was not deferred. I must admit that this stuff happened for two days about 1,500 miles/3 weeks ago--but it disappeared over the course of normal highway driving and did not reoccur until yesterday--although the vibration I mentioned in earlier posts has been going on for almost a week now. Given that this noise and vibration seeming to be related, I'm having my doubts about the motor mount theory, although that could be PART of the problem; it certainly would not account for this grinding and squeaking racket. I found this Nov. 2004 thread entitled "Lots Of Bad Sounds, What Do You Think?" describing a 1990 LS with remarkably similar symptoms. Miles are similar too, at 200K. Based on that thread, I'm thinking serpentine belt, although it would have to be coupled with a bad idler pulley or tensioner pulley. Some people on that thread mentioned a "fan bracket". These grinding noises really sound like a bad bearing(s) somewhere. One person with a great deal of mechanical experience who casually listened to the sound 3 weeks ago concluded the water pump (bearings) were probably bad. I would not be surprised if it's original from 90K, but I'm wishfully thinking it's something else.

That sounds logical, but a bit expensive. Do you all know off hand how much $$$ I am looking at spending for this?

Since last Thursday, my 1993 LS 400 with 206K has begun to shudder when the idle is raised to 1,000 rpm. This "shuddering" is not really violent, but it IS distinctly noticeable and bad enough to make some interior trim pieces buzz or rattle. This only occurs at exactly 1,000 rpm, give or take 100 rpm north or south of that mark. At normal (warm) idle, the revs are down around 600-800 rpm and the engine is perfectly smooth. Start away from a traffic light, and you'll notice the vibration as the tach passes through 1,000 rpm. Above that point, the engine is glassy smooth, like it normally should be. The shudder returns at 1,000 rpm as the car coasts to a stop, or any time it's coasting with the revs around 1,000 rpm. Step on the gas, and it goes away. This is definitely related to the engine, not the driveline, as the issue manifests itself with the car in park or neutral as well as while driving, regardless of gear. Additionally, at about 2,000 rpm, there is a far less noticeable "recurring" vibration, which sort of pulsates once a second. I'm assuming this is related. A friend told me that this whole issue is due to a clogged catalytic converter or exhaust buildup, and that the car has always done this and I just haven't noticed. However, this issue is definitely new, and it started from one day to the next. I've read about bad motor mounts, belts too tight, worn pulleys, or timing belt needing replacement. Could it be any of these things?

SK, prior to having this car, I drove a 1990 BMW 535i for about 46K miles. When I had a tuneup done at 165K miles, the spark plugs, spark plug wires, and distributor cap and rotor were all replaced. So barring a bad ECU, it seems like a tuneup will likely cure any other causes of the problem. The car still hasn't acted up since the Lexus dealer had it yesterday morning, though.

Good advice all! 91L3xus, I may have seen your car this morning (Dec. 8). Is it black in color, missing several center wheel caps? Didn't look THAT bad :-). It was the only ES 250 I saw, and I was there from about 9 to 11:45 AM. I think that car had a gray interior, not a tan one, so maybe it wasn't yours. What were you getting done to your transmission again? 914lps, I have disconnected the battery any time I did anything under the hood related to this problem (including MAF replacement). However, I did NOT clean the MAF before I put it in. Here's why; I tried to clean my original MAF. However, when I took out the three screws, disconnected the plug and pulled it out, I could not see any "little wires" like I have read I will see. There's just a 2-3" plastic piece that sticks down inside the metal box. I sprayed fast-drying contact cleaner on that piece anyway, but when I reinstalled, the car would not even run with my foot ON THE GAS. I was later able to drive it a little bit (around the block), but overall driveablility was not restored until I received the new junkyard MAF in the mail and installed it. And SRK, tachometer always seems to correspond with the actual RPMs--including unruly idle fluctuation. Upon my inquiry, the dealer said they would not charge me for any further diagnosis, stating that my initial $111 would cover any other investigation until they actually began work on the car. As I noted above, they had my car for nearly three hours, and finally returned to tell me that although I drove the car there with the check engine light on, the computer was not throwing any codes at all. Because of this as well as the randomness of the problem with no apparent trigger, the tech believes that the ECU computer itself is basically shot. He was willing to test by swapping in an ECU from a "certified" car, but said it would take another six hours or so before the part was available to him. I couldn't wait any longer, and he assured me that he was pretty sure the ECU was the problem. He said he did "check the inputs and outputs" of my ECU, but really didn't have any other clues. He also stated the car is indeed running "very rich" when the light is on (which must be why gas disappears so rapidly while this is going on and my back bumper is BLACK around the tailpipes). Since 11:45 this morning, I have driven my car off and on all day until now (10:00 PM), with absolutely no problems. I am keeping my fingers and all my toes crossed, but experience up to this point suggests the issue will probably return. I'm wondering how much sense this guy's conclusion makes--or do I really just need a fuel filter or, at most, a tuneup. Remember, there are now apparently no trouble codes when the check engine light is on.

Going to the Lexus dealership tomorrow. Tonight I drove the car, and the check light DID finally come on and the car ran with reduced power. However (I guess because of the new air filter having something to do with it) it does not cut off anymore, nor does the engine run rough anymore--it simply cannot be revved up very high and has greatly reduced power. Still, I can get up to 75 mph pretty easily. ALSO, I noticed that when the light is on, the car blows distinctly black smoke and burns through gas at an alarming rate. It does not do this under normal conditions (without the light). I believe this means the car is running rich (too much gas)?? I will see what the dealer says tomorrow. Thanx again for your inputs.

OK, I will do that. Others I know have recommended I do the same thing, so I feel even more vindicated now. Hopefully this dealership will deliver the "customer service" Lexus is known for when I request a free diagnostic and point out their poor attention to detail the first time.

OK, so--fuel filter (I was already thinking about that), tune up, and then possible fuel pump. Would a clogged fuel filter actually cause the car not to idle--to actually cut off, or idle erratically? When I try to rev the engine up to keep it running, it'll rev smoothly, but the tach needle will rapidly and relentlessly "dive" toward 0000 rpm before zooming smoothly back up in keeping with where my right foot is (this of course is only when the check engine light is flickering on and off). Also, the engine has recently been more smooth if the light is on, but acceleration is painfully slow because there is very little power and the transmission starts out in 3rd gear (I usually shift it manually 1st, 2nd, etc when this happens). Pressing the gas more than 1/3 way down will cause the fluctuation and bogging down, but the engine is smooth while only feathering the throttle. Driven in this way I have been able to cruise at 75 mph. However, the engine feels like it's running either to rich or too lean. I'm super confused how the car can drive with NO PROBLEMS for one or two days (sometimes over distances of 200-300 miles), being parked, restarted, driven, etc.--no issues. And then all of a sudden, the problem returns. It does not seem to be dependent upon temperature, moisture or any other atmospheric factors. Can a clogged fuel filter be great for several days and then cause these massive problems? The check engine light will go away on its own when the car decides to "act right". Last night, it came and went within a minute, all at 70 mph. Do you all think I should take it back to the dealership and demand another diagnostic, this time for free? I can't pay $111 for them just to stick a plug into my engine compartment and read the code. Also, I was chagrined that the first time they did not notice any of the loose clamps on the hoses and try to trace the problem to a simple source, instead quoting me a $1,300 repair. Anyways, thanks for those speedy responses--this a really a great forum!