JeffreyV

I think it could be your throttle position sensor. It's under the hood, attached to the throttle body. You can get one on-line for about $75. If you research lexls tutorials, there are photos and info on how to replace. It's pretty easy. http://www.lexls.com/tutorials/

After new spark plug wires, distributer caps and new throttle position sensor, my engine missing/chugging at 45-50 mph disappeared for 2 months. It has come back (but not nearly as bad) with the cold weather (40 degrees in the morning). I'm thinking it could be the thermistor which monitors the coolant temperature and once warm enough allows the transmission to shift into overdrive or the converter to go into lock-up. I think I'll let the car idle for 15 minutes before I drive and see if it still misses/chugs. Maybe the throttle position sensor setting has changed and needs to be reset. At any rate, my normal car mechanic is good and won't work on a Lexus. He says you fix one thing and something else breaks. I think this is the last Lexus I'll own. I like the car, but it's aggravating.

Most mechanics would say it's long overdue. But, my LS400 is a 1992 and no problems with any hoses. I'd leave them alone.

Let us know what the bill was too!

I have the same problem with my 1991 LS 178,000 miles. Its intermintent and only does it when its real Hot out (90degrees) and the car is fully warmed up. I also just replaced the transmission fluid and the transmission filter. However, I used Dextron III fluid( the valvoline website says the dextron III is fine for this car, but not totally sure). What I think is happening is the transmission is shifting from first gear directly into 4th gear instead of going to second and third.. I am assuming the computer must be gettting bad signals from some sensor to cause this to happen, or a problem with the valve body. I need help on this issue also, I dont want to pay the Dealer more than the car is worth to get it fixed. Before you do anything else, be sure to check the wiring harness inside the trunk. It's in the channel on the hinge on the driver's side. Apparently it can short out and cause all kinds of seemingly unexplained problems. Search for "wiring harness."

I'm having problems with my 1992 LS400 torque converter lock-up. It can't make up it's mind to engage or not. Pleaes let me know if you resolved your problem and if it was the transmission's temperature sensor. I know that they keep the transmission from locking until the car is a operating temp. I was considering trying to disconnect the torque converter - but, maybe it's just a temperature sensor! Write me here and/or at byerjv@yahoo.com THANKS!

YES, IT STOPS CHUGGING/JERKING IF I PUT THE BREAK ON AND MAINTAIN 45 MPH USING THE GAS PEDAL. IF I TAKE MY FOOT OFF THE BREAK IT STARTS CHUGGING AGAIN. THAT'S WHAT I'D LIKE TO DO... DISCONNECT THE LOCK UP FEATURE OF THE TORQUE CONVERTER. I'M THINKING I'LL ASK MY MECHANIC. HAVE YOU TRIED DISCONNECTING IT YET?

I'm still having problems with the car "jerking" when the lock-up feature of the torque converter tries to engage at about 45mph. It comes and goes. Last week the car was fine, but it's been chugging again for four days now!!! I'm considering just disconnecting the electronic lock-up feature. Does anyone know exactly where it's located on a 1992 LS400? Is it attached outside the transmission? Is it easily disconnected? Thank you!

Tony, It sounds like the motor and transmission mounts are the problem to me. After they are replaced the problem you are describing will likely go away. Transmission failures in LS400s are rare. The only failure I have ever heard of was a transmission with over 600,000 miles! For that reason, used LS transmissions are very inexpensive. There is one on my local Craig's List for $100! I don't think you will have to worry about that though. Wasn't there a defect with the ECUs on 2nd-generation LS400s that caused a problem like this? I have seen it discussed on this forum before. Try searching for "ECU" and maybe you will come across the same thread I have seen. ________________________________________________________________________________ ___________ I found this explanation on the internet.... 1991 Lexus LS400 review from North America "The essence of quality" What things have gone wrong with the car? At 485,000 miles this Lexus has been tested. Problems over the 11 years of ownership: 1. Power steering pump leaking badly at 95,000 miles. 2. A 'faint' engine 'miss' between 40 to 45 mph at time of purchase. The torque converter was replaced years later and the problem disappeared. Endless tune up parts were replaced to remedy this problem earlier, but nothing helped until the torque converter was replaced. ................................................................................ .............................................................

The entire surface was coated with black deposits. I used a toothbrush and throttle body cleaner.

I wanted to pass along a little info... My check engine light was on and would go off after I drove about 20 minutes. It would stay off, but come back on after about two or three of those short 2 or 3 mile errand runs. I had my mechanic check and he said it was showing lean mixture on the left bank, but he said that he could find nothing wrong. I lived with the light coming on and going off for almost a year. Then I decided to clean the throttle body... that was four weeks ago. The check engine light has not been on since. :)

You adjusted the throttle position sensor, but did you clean the throttle body??? After 50,000 to 60,00 miles, they can get very dirty. Normally the gas peddle will start sticking, which indicates it needs to be cleaned. A clean throttle body will help air flow smoother and make your car run better.

I don't want to break the covers so how do I pop them off? A friend told me to put some WD-40 into the switch and then blow air into the switch. Do these switches rust very easly? I have had several people say that they should dry out eventually then they will work OK again. Just use a flat blade screwdriver... Insert it under the black plastic, and pry it off... don't pry on that wood insert piece. The entire piece should come out easily. I had mine out a few months ago to clean the contacts on the passenger side.

Instead of disconnecting the hose, plugging the return, fighting to get the hose back on and making a mess, etc. It's much easier this way.... turn the car on and let it run at idle speed. Remove the power steering cap. Use a wet-vac with a smaller hose taped to it so it fits into the reservoir. As the car is running and pumping the fluid, suck some out, down to the screen near the bottom of the reservoir, then refill... keep doing it until you are happy with the color of the fluid being sucked out. (Use a clear piece of hose so you can see the color of the fluid). An added benefit is that the wet vac sucks out the crud that has accumulated on the filter/screen near the bottom of the reservoir. byerjv@yahoo.com

rtd; Alternator dead. Replace alternator with new/rebuild. Clean the power steering rack solenoid filter (about every 30K miles). Flush & replace power steering fluid. Is the power steering filter easy to get to? Where exactly is the filter? I've always checked the fluid but never knew there was a filter. Thank you! byerjv@yahoo.com