VVT-i:

I just got back from inside my trunk!
I popped that cap off and everything looks fine -
I could not find one frayed wire - anywhere.

I checked all my fuses too.

I think you are right about a lose ground somewhere though.

Another observation:
My CD changer works but it is barley audible -
I can only here it faintly with the volume all the
way up.

The dummy light comes on when I press the button
on my shifter to move it in and out of gear.

This is very frustrating.

Anyway, thanks for the suggestions!

 

Hey Lexus Daddy don't get frustrated. At least you narrow it down from your statement that when you press the bottom the dummy light comes on. Now we know you have a short to ground in that circuit.
We'll figure it out. Or if you go to the shop to fix this at least they don't sell you a tune up, injectors clean or transmission flush and the problem still there..right. May be pop the wood cover around the shifter and look around that area for the heck of it.

 

Sorry about that earlier post with the transmission connected to the differential. Turns out the repair site I use threw a TSB for an ES250 into the LS400 section. The ES250 uses a transaxle and this has a flow of fluid from the transmission to the differential.

 

VVT-i,

FYI - I found out that dummy light was correct,
I had a rear brake light bulb out, replaced it
and the dummy light is gone!

LOL!

 

Hey...well i had the same problem with my Lexus ES300. IT would hesitate and then come out fine. The problem was all my wires need to be changed. (Spark Plugs, Cap Assy. Distrubutor, Rotor ***. Distributor, and a whoel new cord set). After I that changed it was driving like a new car. IT cost some $$$. I spent $600 getting that all done. Good Luck

 

The problem could be the TPS. Either is the primary or secondary TPS.

 

That is if you have traction control you have 2 TPS's.

 

Sounds to me like the plugs or even plugs wires. they will give you that same hesitation if they are old.
especially the wire if it is crimped. how long has it been since you replaced plugs, wires, rotors and caps?
and changing the fuel filter? that is suppose to last forever. Lexus claims if you have a bad fuel filter they want to see it. and will pay for replacement and shipping. ask your lex dealer about it. Same goes for upper and lower radiator hose. should never need replacing under normal conditions.

 

I believe that the hesitation/slow accelation was just a characteristic of the original model. I had a 91 LS400 and it was a complete dog off the line from the time I purchased it in Mar, 95 w/ 67k miles. ES300's could take it pretty easily off the line. I recall reading that 0-60 times were in the 8.8 sec range. The change in the 95 model brought alot more off the line acceleration, even though hp & torque only increased 10 each. The trans & torque converter were recalibrated to give much better off the line performance, to the tune of 0-60 times going down to 7.0 sec. The 98 model year got even sweeter with the addition of vvt-i and another recalibration of the torque converter and 0-60 times of 6.4 sec. I don't think there is much you can do to improve the performance of the original model unless you swap out the torque converter to a higher stall speed aftermarket model, which should make a pretty substantial difference.

 

Lexus Daddy,

I too would be very interested in what you find out about your hesitation problem. After a couple trips to the dealer to address the hesitation problems in my '94, I was told that there was an inherent hesitation in the '94 that could not be fixed. This may apply to the '93 as well since they are essentially the same car. I had the plugs, wires, cap and rotors replaced (~$400) only to have the same problems. This is when they told me this was "normal" for the '94. They had seen this problem many times before, and even called Lexus on my behalf while I was there to see if there were any new "cures", but none were available. On my own, I replaced the TPS with the new P/N that Lvangundy suggested, but that still didn't help. After talking to one of the senior Lexus techs in-depth about the problem, I also replaced the EGR valve (grasping at straws), but of course that didn't help either. The air filter was replaced, and the throttle body cleaned during the 60K service, but the hesitations were still there. I even ran some very expensive gas treatment through several tanks after reading a post here on CL, but that didn't help either. I did notice that the hesitations didn't occur as often when in the PWR mode, but in my case they still did. I will say that after driving in the PWR mode, I didn't want to go back to Normal. That car was awesome in the PWR mode.

Please keep us informed. I have read on this forum and also Edmunds TownHall about LS400 hesitations, but no one seems to be able to diagnose and fix. I wish you the best of luck as I know how frustrating this can be.

 

Abcedefghij

 

I have a '92 LS400 with 134k I just bought two weeks ago. This car has an occasional hesitation if I accelerate a certain way also. Thought I'd post because in the course of purchasing my first Lexus, I drove 8 LS400's within 2 weeks and 3 of them had this hesitation problem. Seems to be something inherent in the design maybe of the fuel injection.
I plan on doing the plugs and wires in a month or so and will keep you all posted on any improvement.

 

Question: Does this hesitation occur as a jerky surging feel though the whole acceleration?

Do you press down on the throttle ½ to ¾ and it feels very sluggish?

This is what is going on in my 93 LS 400 W/102,000 mi. .

My car has torque and smooth acceleration for about the fist 5 to 19 minutes that i drive in the morning. Then it goes down hill from there.

Amongst my armature diagnosing found that if I unhook the battery cable to reset everything and then go drive it immediately after it run smooth and without hesitation for about 5 to 10, then down hill again. I stop lift the hood and repeat the battery cable unhook. The thing runs good again for 5 to 10.


Question for all to ponder: Is it a bad sensor or sensors that are sending bad info to the computer? Is the computer adjusting for bad info causing hesitation and sluggishness? Does the cutting of the power to the computer reset it back to stock settings (fuel mix, transmission settings ect.)

I don’t know. But for all having this problem try the battery hook, re-hook and drive a couple of time and see if you get the same results. If so then what next??

 

Well from what you saying it sounds like the computer is bad but that doesn't make much sense. The computer either works or doesn't. No in between, and the data used to set the adjustments is set data, no way of modifing it like with firmware. Then again, I'm no experct just my 2¢

 

When you reset the EFI ECU, you are reverting to original programming. The car is adapting the for conditions present thus you notice degraded performance. Find the problem and it will run properly.

This begins with tune-up, fuel system and proper function of all the EFI sensors: O2, TPS...
The obvious things: air filter, spark plugs, plug wires.

If you have a bunch of gunk built up between the radiator and A/C condensor those radiators are not able to properly shed heat and may also inhibit engine perofrmance. But you may notice this as the engine running hot.