jersey1

When the car is first started the rpm's are high until it warms up. but if i dont wait for the R's to drop completely it makes a HARD LURCH FORWARD when i put it in drive but that dosn't happen in reverse why is that and how can i fix it. Thanks for all your help.

tenpointed

I used to have a 95 LS years ago and remember a similar situation. But I really don't remember a loud bang. More of a hard lurch forward. Is this what you're talking about? If you get a loud bang then maybe your motor mounts are worn and need replacing because your engine would be shifting back when you put it in gear at high rpms.

jersey1

Yah a hard lurch forward. not a loud noise that was my mistake so do you know what the problem is and how to fix it.

Lvangundy

Like Dave said..possibly motor and transmission mounts.

On the extreme side it could be your transmission having problems. Have the 2 motor and 1 transmission motor mounts checked and replaced.

LIGHTYEAR

There is nothing wrong with your car. If you put the car into D when the engine is still cold and reving at around 1200 you are going to get a bump. The automatic choke is keeping the revs artificially high to compensate for the fact that the car is not at operating temperature.

Once the car is warmed up and the revs have dropped to around 450 - 550 that into D bump should disappear.

IMO there is nothing to really worry about.

jersey1

Im sorry i have owned many cars and I mean many cars and this is my third lexus and no car is supposed to do that especailly a lexus. and im sure that every one will agree with me on this, once you step on the brakes it should not lunch that hard when put in drive. Now if you dont step in the brakes it should bang hard when you put it in drive, but im sorry No lexus should do that reving at a normal R's before it heats up.

tenpointed

You could always have the dealer adjust the throttle control to lower rpm's. The only problem with that is when the engine is warm, your car will idle low and may die from time to time. I remember that happening on my old 95 when it was cold outside.

spxChrome

If it is shifting smoothly I would put money on the motor mounts. If they are collapsed the engine will shake the car when it switches gears. Have the dealer check them next time you have it in the shop.

My 93 doesn't jump but when I switch between D, R and P I hear a tin clicking noise. Also, when I put in drive after parking on a steep hill it clanks some. Have no idea what that is??

XxLS400xX

Funny how i hear the same sounds in the same situations.

TomWahjudi

I believe that clicking tin sound is just the shifter mechanism, pins and springs work as a ratcheting action. Even my '95 with gated shifter does it. The clank going out from D is probably just the big pin in the tranny that locks the drive wheels disengaging. Remember that this pin is loaded by the weight of the car and you are forcing it out to disengage. If this concerns you, (when parking) shift the tranny to N, engage parking brake, release the service brake so the parking brake can take up the slack in suspension movement (and make sure the car doesn't roll away !) and then shift it to P. Next time you are shifting from P to D, the locking pin is not loaded, thus the clank should be gone, unless your parking brake doesn't work (and the car rolls forward until it the pin holds the car in place). This clanking noise also happens in almost any automatic car parked at an incline (/decline ?).

Regarding the hard lurch during engine warm-up mode, that's just logical. When the engine is at 1200 rpm or so, the torque converter is engaged. Why a healthy and torquey V8 needs 1200 rpm during warm-up mode is beyond me, the way I see it, 900 rpm would have been enough but then again I'm not an engineer specialized in this field. I guess they could have put in another line of code in the ECU programming to lower the cold idle speed and/or retard timing even more when the shifter moves out of P or N. Anyone want to try ? I have a spare '95 US-spec ECU/ECM sitting around collecting dust

Enough about this, don't be complaining no more

LIGHTYEAR

Ditto ! + thks 4 your supporting comments...

azari

Well, here is the thing with my '91 LS400,

I experience everything stated above, except that even when the car has warmed up and the RPMs have dropped, there is still a lurch forward or backward (depending on R or D). Now this lurch is not as bad as when the car's cold, but still. For instance, on my mother's 2000 Camry when you shift in and out of gear (D or R) you don't feel a thing once the car has warmed up. I mean literary the car just doesn't move back or forward and it's REALLY smooth. So could it be that I have a bad tranny or engine/tranny mount or is this normal for this car and you experience this as well? The LS shifts beautifully through gears while driving though. What do u think?

TomWahjudi

Azari,

I think it's just the age of the tranny, your car is 9 year older than your mom's Camry. Try to replace the tranny fluid, see if it helps. Replacing the tranny with a brand spanking new one will help too

azari

actually I did a refill/drain on my tranny a month ago, but no flush. no difference. Wish I did the flush though. Also wish I could get into someone else's LS400 and see if their's does the same thing as well...

azari

hey guys,
I don't know if any of you knows Pat Goss; well he's a well known auto specialist/mechanic who knows all about cars... he has a radio show in my area and I was listening to him today. Some guy called in today to ask him about his problem with his '94 Acura Integra. He said that his tranny also engaged firmly with a little lurch as he put his car in either D or R. It was also interesting for me to hear that the level of firmness while engaging was not constant all the time (somtimes more firmly, with bigger lurch, and somtimes smoother). This is also the case with my car. Pat Goss Diagnosis: engine mount. Regarding the inconsistancy of the engagement he said that it had to do something with the liquid of the liquid-filled engine mounts. I'm thinking that's what's happened to mine, in which case I won't bother getting it fixed. Because my tranny shifts beautifully with no sound and the liquid has no small metal particles in it either, and doesn't really smell burnt. Just a little brownish.