I have a 93 Ls400 when i bought the car it ran fine when i gave it full throttle it would accelerate quickly, after 2 weeks the gauges went out on the car and the acceleration was affected i could only push the pedal down half way if i pushed it anymore it would jerk back and forth and lose power like it was starving for fuel, i recently got my gauges rebuilt for $90 they work fine but the problem with the acceleration has gotten much worse i can barley push down on the gas max speed of 30 to 35 mph if i give it any more it acts as if it wants to die and loses power ive also noticed the amount of gas the car has been using it has been drinking it as if i had a hot rod, have had it looked at and the cats were clogged up so i cut the cats off and installed thrush dual exhaust on the car, have also had the tps check it was fine, i just recently replace the MAF, spark plugs wires and all that, though the original spark plugs were in it they were burnt up, still no luck. . i have also made sure the insulation under the hood isnt affecting my air flow still no luck, the only other thing i can think of is the ECU being bad but im not sure, dont want to take it and have it put on diagnosis seeing as many people have went and had it done and the few small faults that showed up when fixed didnt correct anything i have sunk alot of money into this car, it only has 150K miles on it and i would like to keep the car dont have money to get another, any suggestions would help!! i just want my lexus to be the 250hp lexus it was before!! please help!

 

If the cats were hot thats a sign of bad coils well documented on this site

 

You think so? even though it seems to act the same way as all the other lexuses that have this issue except mine has gotten worse fuel filter changed still same thing, im just at a loss for words would hate to have to get rid of it but it seems to be my only option latley im spending so much money on this car and i just dont know if its worth sinkin anymore into a car thats about 20 years old. . =/ is there any way to check the coil packs?? im just stumped i love projects but this one has me, as ive read about 50 to 65% of people with this issue never seem to get it fixed even lexus mechanics seem to act as if they have no clue. . .

 

See attached pdf for how to test the ignition coils. If they turn up ok I would guess that you have a problem with your fuel delivery system. Probably the fuel pump. This topic could help: https://www.clublexus.com/forums/mai...em-solved.html

But it could also be a problem with your ECU. Do you have any CEL's? See http://www.lexls.com/tutorials/intro/codereading.html on how to read the trouble codes. If your CEL does work (light up before the car has started) but you don't get any response from the ECU when trying to read the codes then it's probably your ECU thats bad. If so, you don't have to get a new one, you can get it rebuild. Google it or search for LS400 ECU (or ECM) on ebay and you should found some companies who does this. I found this one, http://cgi.ebay.com/ebaymotors/LEXUS...item588bd2c263
Or you can buy a ECU thats already are rebuild like this one, http://cgi.ebay.com/ebaymotors/LEXUS...item27b41df22a

 

my car in shop, has been "drinking" gas last week before ignition coil went last thursday..while driving, lost power, but still drove, but not fast...guy has now replaced the coil, and is oging to see if he can determine why the "check engine" light is on...told him to go ahead and diagnose...always, since ive had my 93 ls 400 (three years), when i drive about 40-45, it chugs, like choke problem.lexus mechanic that i used to go to, says that is "normal" for that model..i just ignore it, it normally drives great, has great power, change the oil regularly....hope this one coil does the trick, but will do what i need to do..

 

Hope you get it figured out but he changed the coil and now gonna see if he can determine why the light is on? It's probably on b/c the coil was bad. But check anyway using the link from lexls.com.
Your old Lexus mechanic, says the chugging is "normal for that model"? I would say common, but not normal. Did he ever say what it was? Maybe that is why the engine light is on now. My 93 does the same thing at the same speed, along with other members' 1st gens. (mainly 93s) I'm willing to bet it's either your TPS or AFM. Here's how you can test them; https://www.clublexus.com/forums/sc-...on-issues.html It could also be your ECU has some bad capacitors that need to be replaced, I think that's the problem with mine.

 

ignition coil

 

Hello,
Just recently had my 93 LS400 fixed for the same problem. The mechanic I took mine to specializes in Lexus. When I told him how the car was acting and that the code was reading a bad TPS, he immediately told me that the car more than likely had a bad computer. He went in, pulled it out, looked in it, and told me that it was "fried." I sent the computer to a plce in Tennessee to have it rebuilt for $149. I got the computer back in about a week and the mechanic reinstalled it. The car rides perfectly!!!! The website for the company that rebuilt the computer/ECU is autoecu.com. They are great to work with and they also rebuild instrument clusters, etc.

 

I dealt with a similar problem recently in my dad's 93, where it would barely crawl along even after he stomped down on the gas, the revs would climb but the car would buck and not gain speed or gain speed very slowly.

Without driving it, my thoughts were;
Ignition coils
Tranny
ECU

Tested my coils with a multimeter and the ohms were not within spec. Replacements from rockauto weren't either... but installed anyway with new spark plugs I had been meaning to install. Checked resistance for spark plug wires all were well within spec.

Took car for a spin and still exactly the same issues. Should have test driven it beforehand, it was definitely the tranny after I noticed how it drove and acted in reverse gear. Guess my multimeter didn't go low enough to give me accurate readings on the coils.

Tranny fluid was red and unburnt via dipstick, decided to drain, pull the pan and replace the filter/strainer. Filter was clogged for sure, bottom of pan was dirty as were the magnets. All clean, new filter, had to retap the drain bolt since whoever worked on it last strpped it, but after it was all put back together and topped off it has been running fine since. Drove it to work today just to make sure.

Anyway, guess the filter was only letting fluid through part of the time causing sometimes erradic issues as the sediment moved enough to let fluid through or block it completely.

Not exactly fitting your symptoms but another thing to consider.

 

I changed both coils and it no longer stumbles. But the remaining routine maintenance acts wont hurt!