elvis

Liam is right, you probably lost one component in the chain. You can swap ignitor connectors and ignition coils since they are the same on both sets of four cylinders. See if you can get the other bank to have spark. One ignitor cable is slightly different. It has an extra wire to drive the tach but you can swap it to isolate the bad part. You could also have a cable problem going to the pick-up coil in that side's distributor. I did. My fan belt ate through it when I didn't tie-wrap it. Congratulations on doing a lot of work. It will pay off. Let us know what it was. Elvis

Cheers to you Liam. Sounds like they got it. Elvis PS: It would be worth it to pull the EFI/ECM fuse for 10 seconds with the car off then put the fuse back in. Start the car and let the computer automatically revise its fuel map now that you are firing on all 8. Expect a few minutes of it getting the right solution to fuel/air ratios. This will erase the biased map it had from running on 4 cylinders. Then go out and get up to speed for 30 miles or so to get the Cats up to temp and clean them out.

You're welcome. Let us know what they find. Elvis

90LS400Lexus, I would definitely check the easy things first. The tires could have taken a set but that should go away if the tires are brought up to temperature a few times for, say, 30 minutes at 50 or above. The trans mount is most likely sagged at 200K miles. That can be looked at easily if the car is on a lift. Its a simple 15 minute job once its on the lift. With that mileage, I would bring one with me and have the mechanic just install it. I actually bought mine new on eBay for under $50. It was a new Lexus OEM part. I think the Lexus dealer price is around $80. When they sag, a lot of engine noise and vibration gets transmitted to the steering wheel and floorboard. That's probably not all your vibration but it will make a good improvement if it is sagged. Note that many good mechanics may not know what a bad Lexus trans mount looks like but pictures are earlier on this post. Bad front lower or upper ball joints can cause a shake/vibration. A qualified mechanic can check those easily. Last would be the drive shaft and center U-joint. There is also a center bearing. This gets expensive and tougher to diagnose. I would keep it in mind because of the mileage and the fact that you have symptoms which could point to it: Steering wheel vibrations starting at a lower speed, drumming or humming sound, and 200k miles on the car. I could not tell mine was bad until I had the drive shaft out and the two sections separated. Then I could feel a notch in the U joint as I moved it. Its a pain to pull it just to check the u-joint. I could not locate just a U-joint which is usually a $20 part. Lexus sells only the entire assembly. The drive shaft was $928 from Lexus but it did cure my particular problem. There are rebuilt drive shafts advertised but I couldn't actually find one in stock to fit a 91. You would have to find a trusted mechanic willing to work with you on the diagnosis and not want to replace it unless it was actually bad. Elvis

Liam, Here's some possibilities: Make sure Doug verified he is actually getting a good spark at plugs that originate from each distributor/igniter/coil circuit. I say this because my coil passed the resistance test in the shop manual but would not produce a spark. Other possibilities are: 1. Timing belt jumped a few teeth (has the timing belt been changed once? Think you said you have over 150K miles) Doug can verify this easily with a timing light. Hope he knows Lexus. The LS400 uses # 6 to time, not #1 like a lot of cars. Lexus belts are good belts. I changed mine at 90K and it looked new. Still, its an easy test with a timing light. 2. Low fuel pressure (fuel pump or blocked filter). 3. Bad or disconnected Mass Air Flow sensor. 4. Some sort of huge air leak between the MAF and the Throttle body. Should be able to see something that big. Large crack in the bellows or a major vacuum hose off. 5. Something blocking the air flow going in. Can't imaging what this would be. Good luck and let us know what it is. Elvis

I agree 100%. The rebuilt driveshaft finally came. I will send it back. Although advertised on-line to fit a 1991 Lexus LS-400, the front drive shaft section was a different design and 2 1/2 inches shorter in the spline than mine. Not enough spline length to adequately join it to the other section and no locking nut like mine has to secure the spline to the other section. I don't know what car it came off of. The biggest disappointment was that it was not rebuilt as advertised. Under the fresh flat black paint was a rusted, apparently used U-Joint and center bearing. This for almost $500. I have never seen a rebuilt part come in in this shape. It was obviously pieced together from parts, somewhat cleaned and sprayed black. One other detail, it was phased wrong in the yokes and could not be corrected due to a keyed spline. Ordered one from Lexus today (ouch!). Elvis

Pishta, sorry, I was away from the computer awhile. Always glad when someone else wants to solve these problems too. Here is some data: Sizes needed for a 1991 Lexus if you are planning to re-stake it: Required Span (cap outside edge to cap outside edge, called “outside lockup”) 2.929 inches. Required Cap Diameter: 0.972 Inches The closest I have found is A GMB U joint (part number 2207284) for a 1990 Mercedes 300 SL Span: 2.929 inches (OK) Cap Diameter 0.945 inches, need 0.972 inches (too small) Here’s a link to the GMB .pdf catalog: http://www.gmb.net/members/catalogFrame.htm Here is a link to the Mercedes U Joint that almost fit from Advance Auto Parts. http://www.partsamerica.com/ProductDetail....tNumber=2207284 It looks very similar to the Lexus U Joint I pulled out. Note the rolled edges on the bearing caps on the inside. As far as I know these u joints are only used on a few cars like the Mercedes and the Lexus. Here’s a link where I found the info on the Mercedes drive shaft. It mentions Lexus as being a similar design. It is a very special design and a very special U Joint. Link: http://driveshafts.com/pages/mercedes_ujoint.html Here’s a quote: “The Mercedes universal joint is quite interesting. Unlike most designs, the roller bearings are contained in a thin shell, stamped from an exotic alloy sheet metal 1 mm thick. It is formed accurately enough to not require subsequent machining and is heat treated sufficiently by the force of the stamping to not require subsequent heat treating. The thinness of this bearing cap allows a large cross and larger roller bearings to be utilized, greatly increasing both strength and bearing life, while keeping size and weight low.” Glad to hear you are a manufacturing process major! I believe you are on the right track and this problem can be solved. There are other U joints the right length and a slightly bigger diameter. A machine shop could bore the 4 holes required without much problem. If done carefully, I don’t believe the balance would be affected enough to notice. With the right instructions, they could also cut the cir-clip grooves so that staking would not be required. I had to get my car on the road again so I went ahead and ordered a replacement drive shaft for a little over $400 from PartsTrain.com. I thought at least its better than the $928 from Lexus and my labor is free. It was hard to find. Some companies advertise it but aren’t handling it anymore. I’ll look at the one I get in a few days, especially what the u joint looks like. Maybe it will have a number on it. I will post it if it does. My guess is that it comes from Japan and its made or rebuilt there. I did look into the cost of a single-piece driveshaft. Not a bad option but by the time you modified each end to accommodate the Lexus flexible couplings, its about the same cost as a rebuilt. I would be careful too about using the couplings on a long shaft. It may need a U joint on each end to accommodate differential vertical movement. Lexus didn’t take the one-piece option because of possible harmonics and vibrations from a longer shaft. Their goal was a world-class smooth, quiet car which they succeeded at. My son has a Turbo Supra (a fore-runner to the Lexus in many ways). He will probably go to a one-piece. It’s a very similar design to Lexus but it has a u joint on each end rather than the flexible couplings the Lexus has. Our other friend did go to a one-piece and is pushing 650 Hp through it. He isn’t concerned with vibration however. Elvis

I pulled the drive shaft out today as well as the transmission mount. The driveshaft has a single u-joint in the middle near the center bearing. Mine is definitely bad. Should have caught it the first time. You can feel that it is grooved when its moved. Its very rough. Feels and sounds exactly like what I feel in the steering wheel and gas pedal. I have high hopes. I'll know in a few days. The u-joint is staked. No one lists a part number for it since they consider it not serviceable. Easy to get around though. Its a common u-joint. I’ll replace it with one that has the in-board cir-clips rather than staking a new one. The trans mount looks like its seen better days. Its not broken but the rubber is soft and flattened Will change it and the driveshaft center bearing. Elvis Well, I started this thread so Ill add again to it. I replaced my rear carrier bushings and that helped about 90% meaning it has reduced the vibe to about 10% of what it was. My shafts were twistable with my hand so I found a set of bushings on craigslist for 40 bucks, too good to pass so I did them and WOW, what a difference. My bushings didnt look bad, they were just soft. It is hard to see in there because the location of the bushings, but I got then out, put the new ones in and drove around. No more rear end wandering and the vibration from the rear seems to be gone. Im going to look into the driveshaft U-joint. ANy cross reference for a part number? Taking it into a supplier Monday or Tuesday to match it up and get one with the retaining clips on the inside. I'll post a number for it. Note that I didn't notice any trouble with the U joint by turning the drive shaft while in the car. It felt smooth then. (It didn't feel smooth when I had the car running on jackstands at 38mph Anyone reading this, be very careful of this procedure). When I had it on the bench and the two sections of the drive shaft disconnected, then the groove and roughness could be felt when I moved it in either axis. It has 173K miles on it. Probably started going bad at about 150K. Elvis Update: (and to mwc0610) Looks like I do not have the solution I thought I had. I removed the U-Joint with a "C-Press Ball Joint Tool" from Harbor freight. What a tool! On sale now for $29, without shipping. Its a copy of the Matco Press. Had no trouble getting the U Joint out. It is very bad, very rough and grooved. The bad news is that I cannot find a replacement. I downloaded catalogs from major U-Joint suppliers like Neapco, Rockford and GMB. No one lists the size required. I did find that it is a very special U-Joint as is the entire drive shaft. Its a design similar to the Mercedes, circa 1990. The Mercedes U-Joint came the closest. Right length, wrong cap diameter. Unless I have a breakthrough tonight in finding one, I'll order a rebuilt driveshaft. (to mwc0610) I wish I could find a correct U-Joint to install. Lexus is great but I can't understand why they didn't make this driveshaft more serviceable. At least the new driveshaft will have a new center bearing and be balanced. The center bearing is available on-line at Parts.com for the 1990 thru 1994. I am not familiar with the 1995 LS400 but I assume it has a center bearing too. I didn't see a 1995 listed at Parts.com. Its a little rare but you can probably find it. So many things can cause vibration its hard to pin down, especially if its a driveshaft. My car fooled some real experts that I ddeal with all the time. I couldn't be sure until I had mine apart. But as others have said, try the simpler and cheaper things first. Looks like you did that already though. For the forum: Any recommendation on a good drive shaft supplier? Elvis

I pulled the drive shaft out today as well as the transmission mount. The driveshaft has a single u-joint in the middle near the center bearing. Mine is definitely bad. Should have caught it the first time. You can feel that it is grooved when its moved. Its very rough. Feels and sounds exactly like what I feel in the steering wheel and gas pedal. I have high hopes. I'll know in a few days. The u-joint is staked. No one lists a part number for it since they consider it not serviceable. Easy to get around though. Its a common u-joint. I’ll replace it with one that has the in-board cir-clips rather than staking a new one. The trans mount looks like its seen better days. Its not broken but the rubber is soft and flattened Will change it and the driveshaft center bearing. Elvis Well, I started this thread so Ill add again to it. I replaced my rear carrier bushings and that helped about 90% meaning it has reduced the vibe to about 10% of what it was. My shafts were twistable with my hand so I found a set of bushings on craigslist for 40 bucks, too good to pass so I did them and WOW, what a difference. My bushings didnt look bad, they were just soft. It is hard to see in there because the location of the bushings, but I got then out, put the new ones in and drove around. No more rear end wandering and the vibration from the rear seems to be gone. Im going to look into the driveshaft U-joint. ANy cross reference for a part number? Taking it into a supplier Monday or Tuesday to match it up and get one with the retaining clips on the inside. I'll post a number for it. Note that I didn't notice any trouble with the U joint by turning the drive shaft while in the car. It felt smooth then. (It didn't feel smooth when I had the car running on jackstands at 38mph Anyone reading this, be very careful of this procedure). When I had it on the bench and the two sections of the drive shaft disconnected, then the groove and roughness could be felt when I moved it in either axis. It has 173K miles on it. Probably started going bad at about 150K. Elvis

I pulled the drive shaft out today as well as the transmission mount. The driveshaft has a single u-joint in the middle near the center bearing. Mine is definitely bad. Should have caught it the first time. You can feel that it is grooved when its moved. Its very rough. Feels and sounds exactly like what I feel in the steering wheel and gas pedal. I have high hopes. I'll know in a few days. The u-joint is staked. No one lists a part number for it since they consider it not serviceable. Easy to get around though. Its a common u-joint. I’ll replace it with one that has the in-board cir-clips rather than staking a new one. The trans mount looks like its seen better days. Its not broken but the rubber is soft and flattened Will change it and the driveshaft center bearing. Elvis

Thanks! I read the whole story. WOW! You stuck with it and found the problem and the post helped a lot of people. Sounds like you got good prices too. The Lexus can be so smooth but there are a lot of potential causes of vibration. I'll let the forum know on mine. I used to be into early Corvette's and had to change U-Joimts quite often. I should have thought of that earlier. Mine has the red, rusty powder around it like the bearings have ground up after it went dry. So, I am hopeful. May be awhile before I can get to it. Elvis

Thanks for the reply. All were good suggestions. Some of the data about past fixes were on earlier posts. A summary is that I started with tires. Tried two known good sets from other cars, tried rotation and a couple of balances. I ended up putting the new Michelins on anyway since I needed tires. I knew I had a tougher problem since all the tire swaps over the past six weeks had no effect on the vibration at 38 mph at all. It is very smooth over 60 mph. I did have worn lower ball joints earlier and had replaced those not too long ago. They were significantly worn due to a design defect in the earlier ears, I think 90 and 91. I decided to tighten up the whole steering and suspension due to "wandering" and a lose feel in the handling. It also had a shudder when I came to a stop (one warped rotor in back). I got going and replaced the upper ball joints (not too bad though but expensive), lower control arm bushings (very bad), inner and outer tie rod ends (medium play) and rear trailing arm bushings (very, very bad, almost no rubber left that was doing any good). I have to say that the handling feels like a new car now and its a real pleasure to drive. I would recommend this to any serious do-it-yourselfer if you have the skills or a good friend you can learn from. It is a lot of work. I used after-market parts, and some from EBay (all new parts though) to save expense except the lower control arm bushings which were actually cheaper at the Lexus dealership. When it was complete, I took it in to a known, good alignment shop. It was satisfying doing the work but note that I also have a friend with a 20-ton press which helped a lot. Even with that, there were tough spots. By the time its over, I'll probably have gone through the whole car. Next is gauges and the LCD display. If anyone has changed the drive-shaft U-Joint and has had some effect, please let me know. Thanks Elvis

Hi This is Elvis, I didn't find any noise, rumble etc. in the front wheel bearings either under load or not under load that may be causing the steering wheel vibration. I went on and pulled the driveshaft. The U-Joint in the center of the driveshaft had the tell-tale red dust around it indicating the needle bearings got dry of grease and ate themselves up. Center bearing feels ok, but I may go ahead and change it. The vibration was faint about two years ago. It has become very pronounced. Its started at 35-40 mph but broadening out now to 30-60. Its about 25 HZ which is the right frequency for drive shaft revolutions at 38 MPH. I'll let you know. BTW, the new Michelin Primacy tires and suspension parts really restored the steering to what a Lexus should be. What a pleasure to drive. The Akebono ceramic brakes are great also. The trans and engine mounts looked good and passed the torque test but its hard to tell. They didn't move much.