gqr1c3boi

Hey guys,

I've got a 99 LS400 and when i accelerate (1200 - 1500 rpms), usually on a cold start, the gas pedal vibrates. It doesn't do it any other time except on cold starts. Does anyone have any ideas? it's got 75k miles on it.

Thanks

Neofate

iTrader: (1)

Hrmm.. an easy fix for sure. Trying to think what link cold and gas pedal has.

First thing I'd check is the throttle cable by the intake (near Throttle body) -- Lube it up,.. make sure it isn't sticking somehow by the cold weather.

It sounds mechanical, some linkage of some sort -- Nothing else is going to make the pedal itself move besides a part from it to the cable by TB. So should be fairly easy to trace.

Do what I said, and then if it continues -- on the next cold start, trace it all the way back.. Look up under the pedal first and listen and move things around. Then go into the engine and trace the linkage all the way to the intake.

PureDrifter

iTrader: (10)

too bad the 98-00 LS were drive by wire....


are u sure just the pedal is vibrating or that whole floor area?

gqr1c3boi

yeah, it's just the gas pedal.

PureDrifter

iTrader: (10)

hmm, il look into my manual, maybe there is a backup cable conncetion

Neofate

iTrader: (1)

I thought of that.. But still applies, it is some linkage somewhere from pedal on back. It is the only thing that could make the pedal physically shake.

GRAND_LS 4

iTrader: (2)

Actually, there is cable that goes from the pedal, across the intake manifold and all the way to an electronically controlled throttle body.

I've had this issue before, make sure the cable is secured where it crosses above the upper intake manifold.

gqr1c3boi

Thanks for the input, I haven't had time to take a look under the hood yet but I'll get to it this weekend. So basically I need to check and see if it's secured and/or lube it up? Exactly what kinda grease would I use?

GRAND_LS 4

iTrader: (2)

Theres nothign to lube. Just make sure it tight and secure, with no play. NO LUBING is involved.

gqr1c3boi

I was just going off what Neo said..

Neofate

iTrader: (1)

Yeah -- I'm just speculating.. It wouldn't hurt to lube any linkage -- WD-40 type spray.. But nothing electrical. Your problem isn't likely from something sticking. If it is sticking then it has been pushed into something it isn't supposed to be on.. or something else on it.

Just check that everything is straight, where its supposed to be, tight, not overtight, brackets are on well.. and so forth. Move it around a bit,.. try to find the problem with feel and visual.

Hap

I think you probably have a cracked or otherwise broken motor mount. This is from experience for, you see, I too once had a vibrating gas pedal. During the 90K service (done at 82K) they noticed and replaced at least one and possibly two broken motor mounts. Poof. No more vibrating pedal.