Devcon

And before anyone says it, I did use the search function!

I just joined this forum as a proud new owner of a 91 LS400 (204k), which is the most wonderful vehicle I have ever owned! Even with problems, she is a stunning vehicle to drive.

Anyways, I have done my share of searching to diagnose these issues but havent found anything exactly like what I am experiencing. Apologies for length:

First of all, After a quick 15 minute drive the car will begin to vibrate at speed, accelerating or braking seems to reduce the vibration, acceleration pretty much eliminates it. The vibration is akin to driving over a wake-up strip or speed strip (little ones before a stop light). At first, I thought it was a flat tire, as it was similar to that whappita-whappita feeling when a tire goes, and it would go away as I sped up, but no, tires are good! And, when I park the car, the RH Rear wheel emits a rather brakelike smell, and after sitting, alot of heat gets transmitted to the rim. None of the other wheels do this. My first guess is a warped rotor, but if that were true, it would vibrate right away, not after some time. Dragging + Warped rotor? Other possibilities I have thought of are a worn wheel bearing, or even driveshaft bearings/transmission mount. Any validity to these thoughts?

Second, since the day I bought the car, the TRAC-OFF light is illuminated constantly. If it helps diagnosing, with the car in Accessory or Ignition on and the engine not started, the TRAC button works. The light toggles on and off. Once the car is started, though, the light is on regardless of however I may press the button. I did the lexls.com thing and wired up the ODB port, and the TRAC-OFF light started flashing... and flashing... wait, isnt there supposed to be a pause in here somewhere? It just kept flashing for as long as the car was on... I did some looking, and apparently that means everything is okay, which makes no sense to me at all; If that were true the ABS and Engine lights would also flash constantly. For me, "everything OK" would mean the light wouldnt start flashing in the first place... And no, there are no other lights on.

Third, when I got the car there was a bit of vibration from the steering wheel and seat, noticeable at idle and while driving, and it hesistated under acceleration, like it was missing. So, I got it home, got all the covers off, pulled the plugs and wires... Most were good (for being the originals!) but the wire for #2 was broken (infinite resistance) and I noticed a small amount of orangeish fluid in chamber #7, enough to obscure the hex of the plug . The part of the wire that went into the chamber had a reddish/orange substance on it, as if the fluid level was much higher at one time. Smelled it, it wasnt oil and it wasnt coolant, nor was is transmission fluid. I sopped it up and let the thing sit overnight, and sure enough, there was some more fluid in the chamber... Where is this coming from? Just condensation or a more serious leak? So I went ahead and changed the plugs, the old ones were Bosch Platinums, so they had been changed before. However the tips were very wet, a gasoline smell, no noticeable oil. Running rich? I put new wires on and put the covers back on, took it for a drive.
AH! My power is back and there is no hesitation! But now I notice there is a slight misfire (?) at idle or when stopped at a light. The engine is smooth, but every now and then I feel a little 'tick', like a misfire, in the engine. No noise, just the feeling of a pause, of sorts. Any obvious reasons I might be missing?

So there are the issues I have been having, apologies for the length, but I wanted to get as much detail out to you guys as possible. This car is truly wonderful, and it has its issues, but what can one expect for 17 years old and 200k+? The climate control LCD is broken, common issue, the sub is dead, also common, but everything is otherwise in wonderful shape. I expect needing to change the bushings/mounts in this car, and will soon be changing the oil, transmission fluid, diff fluid as well as a coolant flush. I want this car to last!

Bali26

First: Your brake caliper is sticking

Second: There should be an error code stored for trac. If not, maybe your trac-off button is acting up.

Third: Orange fluid has to be either oil or coolant or mix of both. There might be a gasket leak, resulting in fluid there and your sparkplug therefore fouling up. Also check out your distributor caps and rotors and coils.

Devcon

Thanks for the quick response!

I will check out the caliper now, hopefully thats all it is.

I'll check the codes again, make sure, but as I said, it just kept blinking, no pauses. Trac button seems to be okay, as with the ignition on 'accessory' without the engine running the light goes on and off with each button press.

Coils are good, checked those when I did the plugs and wires, resistances within OEM specs. Rotors and Distributor caps will be next on my list if it cant be resolved. As for the gasket, I sure hope it isn't! Its odd, though, that the fluid only appears in #7, and not in any of the other chambers. I would assume a gasket leak would include all surrounding chambers. Then again, I don't have much experience working on this engine yet. The coolant in the reservoir is green, but maybe mixing with oil would yield that color.

Devcon

Took the affected wheel off, everything seemed fine. Pushed the caliper piston in flush. Put it all back on, test drove it, and the vibration is gone! That must have been it. If it continues I will have to rework the caliper.

However, I can now notice the engine issues more. When idling at a red light, the engine feels like its missing, and almost sputters. RPMs fall and then rise a little. Most noticeable when in gear and stopped, when in park it isn't as noticeable, but the engine is still doing it. When I accelerate power is fairly smooth and constant, with light misses here or there, it is most problematic while stopped. I am thinking either vacuum issues or distributors?

TRAC light still on... Since I can toggle trac when the engine hasn't started yet, does this affect its status while the engine is running? In other words, if I turn it on, then start the car, is it on? Or does the fact TRAC-OFF stays on mean there is an issue/code (which I haven't found) and the system is disabled for sure? Winter is nearly here and I would like some peace of mind!

ttyR2

Could find a gravel road somewhere and mash the throttle and see if the TRAC system actually works. That'd tell you it's actual status (on or off).

Devcon

Update! I have successfully resolved the TRAC-OFF light issues.

In my efforts to figure out the sputtering after the car warms up, I decided to look at the O2 sensors, figuring the car runs great on start up and goes downhill as it warms up, the O2 sensors must be the culprits.

So I checked one and then the other, and one of them was indeed bad! First it showed 25+ ohms, and after a while it just showed infinite resistance (break). I got a replacement sensor, put it in, and now the TRAC-OFF light is gone! I can toggle the system on and off while the engine is running, and I drove to a little dirt road to test the system while on and off. All I can say is I am glad to have this for winter!

BUT, this did not solve my stuttering/sputtering issue! What could it possibly be? When I checked the other O2 sensor, it said 6 ohms... Now, thats the heating element, so the readings it puts out could be the faulty part, but the ECU recognized the other O2 sensor was fixed, and enabled Traction control, so how bad could it be? The only other ignition-related things would be the distributor rotors and caps, but surely these wouldn't act differently depending on the engine temperature???

As for the vibration, I did some highway testing, and after 5 miles of highway driving it started vibrating violently... The passenger seat was shaking so badly I thought it would break! The vibration continues regardless of speed once it starts, and the rate of vibration changes with speed. So since there arent any whining noises that rules out wheel bearing, and if the tire were off-balance slowing down would eliminate the issue, and if it didn't, it would vibrate all the time, not just after some time.

My only other conclusion, as Bali26 stated, is the caliper. When stopped, there is alot of heat coming from the rear passenger wheel, and a distinct smell of brakes. But when I checked it while jacked up, it wasnt sticking, and the piston moved in and out normally. While driving, once the vibration starts, no amount of braking will stop it, it goes away when it wants to. My only other postulation is that the caliper is sticking enough to heat the rotor to the point where it temporarily warps, enough to cause imbalance, and once the rotor cools, everything is fine... Thoughts?

Bali26

Hi,

The O2 sensors are cheap, if in doubt, just replace them. oxygensensors.com. Just get 2 universal pre-cats by walker.

Vibration's cause could also be engine and trans mounts assuming balancing and tires are ok. Calipers are easy to check ...If one wheel is hotter than other then you know for a fact that caliper is sticking. I don't think calipers sticking will cause vibration.


You can try various combinations like this to pinpoint the cause:
when you are moving at speed does it stop vibrating if u put in neutral?

Sanpete

I don't get it. Is there really any connection between O2 sensors and the TRAC system? I always suspect a bad speed sensor when a TRAC problem shows up, though I suppose there ought to be a code for that (but I don't know).

So many things can cause vibrations. There was some discussion elsewhere of a bad drive shaft u-joint causing washboard vibration.

richonenz

Do your engine and tranny mounts first !!
They are well overdue to be done anyway , so that is a good place to start to eliminate vibrations , not likely to be the drive shaft .
I did a friends engine and tranny mounts about 4 weeks ago and it eliminated the vibrations which seem a lot like yours , he couldn't believe the difference , even at idle !!

Devcon

Sanpete: In my searching I found this post:
https://www.clublexus.com/forums/sho...85&postcount=6
He references the ECU shutting down the TRAC system if the O2 sensor is faulty. This seemed to be true in my case.

richonenz/Bali26: I will take apart the caliper, check it all out and rebuild if necessary. Otherwise I will go ahead and get some transmission mounts. The heat coming off the rotor/caliper on that one wheel tells me that simply must be the issue... I know the tranny mounts are fairly fast to replace, but what about the engine mounts? How much time and any special equipment needed?

Sanpete

What you quote about the O2 sensor makes sense, but it doesn't fit your description, which skips step 1 (no check engine light).

Devcon

Vibrations are the least of my problems.

I went out and got rotors and caps to try and resolve the engine 'misfire'. I installed them today and... it is still 'misfiring'... I have replaced the plugs, wires, now caps and rotors...

It runs great, nice and smooth, when it is started from cold- having set overnight, and completely cooled down. Once it starts heating up the 'stutters'/'misfires'/hesistations become more and more frequent (from once every 5-10 seconds to several times a second). So I suspected the distributors, possibly expansion/cracks... Now I know that isnt the issue.

As I mentioned before, I replaced one O2 sensor, do I need to replace the other? Something tells me however, that fuel mixture wouldnt cause such a 'misfire'-feeling event, but more of a constant lack of power and overall roughness. This is different, as it runs great, but intermittantly 'misfires', I can find no other word to describe it... Its like someone tapped the brakes, but in the engine.

What else could possibly cause this???

Bali26

Oxy sensors are cheap. I would have bought a pair, but i don't think that's your problem.

Try driving with trac fuse out, check for vacume leaks.

If nothing else works, just take it to the dealer, get a diagnose and fix it yourself.

Lexushead

My problems. It may help you here: Engine hesitate like a hickup inconsistently.

1. The problem was one of the old spark plug wires leaking. Sparks intermittenly jump from the wire to the metal next to the timing belt under the timing cover. I bought a brand spanking new set of Bosch wires from partsbin and and one of the wires had imbeded metal shavings in the rubber. Long story short, I gave up on Bosch wires.

2. Misfiring and acting really bad = Check the coil packs, injectors o-rings.
Primary coil should be 0.3-0.6 ohm
Secondary 9-15 kohm

Devcon

Update: I changed the other O2 sensor... now its a little worse. Yes, the wiring is good. My guess is the old O2 sensors gave slightly faulty readings in favor of a rich mixture, which overcame the issues from elsewhere. After replacing the O2 sensors, proper readings are given, mixture becomes leaner, but now something else is making it too lean. I suspect EGR and/or vacuum leaks/blockages. I will check these saturday.

More on its symptoms... It now begins to hesistate/jerk much more quickly from cold, and acceleration no longer makes it go away completely. The effect is most noticable at constant throttle, either at speed or idling. Its almost like the engine completely stopped for an instant, but restored itself. RPMs do not drop significantly, only a slight twitch from the needle.

Most interesting is the nature of the TRAC-OFF light. When idling, if the idle drops below a certain level because of the 'misfires', the TRAC-OFF light goes on. Upon acceleration, it may go away. If not, turning off the engine and starting it again restores normal function of the traction control system.

Acceleration is another curious beast... Easing the throttle causes decent acceleration, but in case of heavy throttle, IE passing, it downshifts if needed, but then just kindof vacillates at that rpm, not really doing anything; It accelerates, but as if I were barely touching the throttle. If I ease off the throttle, and ease it back it will accelerate fairly well. But one would expect sudden and observable increase in speed if the pedal were floored... This too seems temperature-related, as early in the morning it takes less throttle to make it 'do nothing' than when it it warm. Again, it is as if after a certain throttle level, it no longer responds as it should. I can accelerate faster if I ease the throttle in than if I depress it heavily, if that makes any sense.

The search continues!

Edit: Almost forgot... In response to Lexushead: I will be checking the new plug wires this weekend as well, since I replaced the original plugs with new ones, even though only one original plug was bust. That seems to have been where things started getting bad, hmm... Coilpacks are good, I checked those over already, and they are within tolerances. As for the injector o-rings... That sounds like a big job. How difficult are they to get at?