SirLS400

Everything had been going smooth with my 93 LS400, but about a week ago I went to drive down to Miami and when I left my complex I pulled onto the highway and went to give it some gas and the throttle cut off. The engine was still running but the throttle did not respond until I lifted off the pedal and pressed again.

I then learned that at maybe 40% throttle or more, the engine simply disables the throttle for some reason. It's exactly like a speed limiter cutoff I've experienced in other cars, where the throttle is disabled for a second and then kicks back in. Mind you, I can still get to any speed I want but I have to get there at less than 40% throttle, which is a pain sometimes.

The interesting thing is that it only does this in gear. In park or neutral, I can freely rev the engine.

Also, I found that I could manually shift the gears to take advantage of the power in each gear to accelerate quicker with only 40% throttle. So I'll rev to about 3000 RPM and then manually shift to the next gear if I really need to go quickly. Otherwise the tranny shifts on its own at around 2200 RPM with the max throttle I can apply.

Is this a computer issue with the Tranny/engine or a sensor of some sort?

PK_Celsior

iTrader: (18)

thats a weird one. are you the first owner for this car. if not do you know the driving style of the other people that has had it. if anything i would just unplug the positive side of the battery for 20 secs. Let the ecm/ecu reset itself and see what happens after that. with my 95LS im able to full throttle whenever needed.

PureDrifter

iTrader: (10)

sounds similar to the trac cutting in...

avalon42

iTrader: (1)

There is a set of wires going from the throttle body to an ECM. I think there is about like 5 wires. If there is a break in one of them, the throttle wont go WOT and should/will not shift gears...happened on my friend's LS when a rat got in his nice and warm engine bay and chewed one of those five wires...

virtue22

Had the same problem with my 93. It was still drivable as long as I did not go over a certain RPM. I changed the Engine Computer (ECU), worked great. I got a used ECU from someone on this forum in the parts section. Hope this helps.

SirLS400

Thanks, I'm going to try unplugging the battery to reset the ECU, hopefully that will work. It's strange too because I don't get any warning lights about it.

qha_vn

my 90 ls400 seems have similar issue like yours but only when it rains. i notice that when i fly over a water pond on the road, throttle suddenly does not respond. engine is still running but i cant go faster then 40mph. after several minutes, everything comes back again as if there isnt a problem before. somebody says it might relate to trac system

also, when the car stays still in P or N, i can nerver rev the engine over 2000rpm, it just drops down to idle when reaching 2000rpm. However, it can go to 4000rpm on road. strange huh

i asked those 2 questions in some 4r including this one, no answer yet

CelsiorLew

I have the save EXACT problem with my car. Is there a solution to this??? Driving where I live is dangerous with this.

deanshark

Seeing how this thread is 12 years old the ECU fix wasn't commonly known. Read this; https://www.clublexus.com/forums/ls-...capacitor.html
I have same problem and symptoms, for about 9 months now, and I know it's the ECU. I just manually shift (starting in 2) and don't give it too much throttle and I'm good. For as little that I drive the car now (30 miles a week, at the most) it doesn't bother me. Get your ECU rebuilt and you should be all set.