LS4001UZPW

Ok,

I'm having issues with accelerating and my rpm gauge is too high when on certain speed.

Firstly, not sure if my 91 LS400 should be driving at 2500rpm when I'm crusing at 60mph. I think that's too much. But I'm not sure. Also the foot pedal feels hard when I accelerate. On my brothers 90 LS400 the pedal is light and just a tap will accelerate the car. Mine doesn't accelerate fast. Not sure what the issue it. I mean it could be quite a few things but wanna know where to start. Everything else is fine. Fires up with no hesitation. Idles normally between 600-800rpm and stays very steady and quiet.

I already replaced the dirty air intake filter. It helped alot BUT still it doesn't accelerate fast and RPM is still at 2500rpm when I'm going 60mph. It's been eating alot of gas lately. Where should I start with diagnosis?

A tune-up? Check/clean throttle body?

I'm thinking both of those. Any other suggestions? Thanks in advance.

LScowboyLS

yes, both of those, and pay particular attention to the "butterfly" valve at the entrance of the intake, it has to be gunk-free to have nice throttle response, otherwise it can seem "sticky" and hard to push with the pedal, because it is!

on the tune-up parts, the caps, rotors, and engine coolant temperature sensor need to be the real Toyota part (easy to find at 25% off from online parts departments of Lexus dealerships such as Sewell, Park Place, etc.)

the wires and plugs for the tune up just need to be Denso or NGK, no need to go through a dealership

if all of that doesn't fix it, come back and we will get to the bottom of it!!

PS - on the 2500 rpm at 60mph, either your tach is not reading correctly or your car is never going into overdrive. (the latter is more likely)

LS4001UZPW

Thanks cowboy. Yeah the next thing up for this vehicle was gonna be the tune-up for me. Ok so I'll go ahead and do it.

But the O/D issues...guess I'll need to look into it. The O/D light never came up on the dash but I'll see what I can find. Thanks.

Gene01

I believe that the O/D light on the dash indicates that the switch (on the shift lever) is in the O/D OFF state.
Normal (overdrive enabled) is the light off.

LS4001UZPW

Alright guys, need a lil help quickly. Cleaned the throttle body and putting it back together as I post this. There is a cable I can't seem to identify which is hanging loose. Can anyone help me? Not sure if I disconnected it or where to plug it in. I attached a quick video showing it. Can someone tell me what this wire is for and where it gets connected to? Thanks in advance.

LS4001UZPW

NVM. Looks like I got another wire on the other side just the same also disconnected. I think they were like that. Anyways fired the car up without a problem. The pedal still feels hard. I'll take it for a drive tomorrow sometime after work and see how it does.

deanshark

There shouldn't be any extra wires hanging in the engine bay, every wire is for something. Although, that isn't the way it came from the factory with that much wire exposed and with tape on it. It looks like it might go into the firewall b/c of the grommet it has on it. Maybe the previous owner had some kind of aftermarket stuff there, like an alarm horn. People do put some crazy aftermarket stuff in their vehicles. Mine was wired up with lights and siren, previous owner was a detective. I removed all that so I wouldn't be tempted to use it and then get arrested.