Lexus LS400 surging

[Erik Rudbeck]

2000 LS400

Today when driving into my driveway - about 20 yards - and slightly downhill
so I enter with the brakes on a bit, the engine suddently revs up, and the
car jumps forward 2-3 yards. I immediately apply the brakes, but the engine
has already returned to idle. While wondering what happened, it revs up
again - 1200-1300 O/min I think, and tries to make another forward jump. I
brake the car to a complete stop, and put the gear in neutral. For the third
time the engine revs up, and then after a second or two returns to idle.

After that the car behaved normal, and I drove it carefully into the garage.

What could be the matter. Any suggestions?

Also I noticed once in a while that when accellerating the car - like when
overtaking other cars, it seems as if the power surges a little. Not much,
probably a passenger wouldn't notice. Could these two issues be related?

Thanks in advance.

Erik Rudbeck
Denmark

[Ray O]

Post by Erik Rudbeck
2000 LS400
Today when driving into my driveway - about 20 yards - and slightly
downhill so I enter with the brakes on a bit, the engine suddently revs
up, and the car jumps forward 2-3 yards. I immediately apply the brakes,
but the engine has already returned to idle. While wondering what
happened, it revs up again - 1200-1300 O/min I think, and tries to make
another forward jump. I brake the car to a complete stop, and put the gear
in neutral. For the third time the engine revs up, and then after a second
or two returns to idle.
After that the car behaved normal, and I drove it carefully into the garage.
What could be the matter. Any suggestions?
Also I noticed once in a while that when accellerating the car - like when
overtaking other cars, it seems as if the power surges a little. Not much,
probably a passenger wouldn't notice. Could these two issues be related?
Thanks in advance.
Erik Rudbeck
Denmark

Engine surging is usually related to one of the following:
* Driver is applying the throttle instead of the brake
* The floor mats are interfering with the throttle pedal - check to make
sure the floor mats are not touching the throttle pedal.
* The EGR system is not working properly - EGR problems are usually related
to surging while at cruising speed or very poor idle
* The idle air control valve or IAC control system is not working properly
(you can try cleaning the IAC with carburetor or throttle body cleaner
* The air conditioner idle-up circuit is not working properly
* The power steering idle-up circuit is not working properly.

[Erik Rudbeck]

Post by Ray O

Post by Erik Rudbeck
2000 LS400
Today when driving into my driveway - about 20 yards - and slightly
downhill so I enter with the brakes on a bit, the engine suddently revs
up, and the car jumps forward 2-3 yards. I immediately apply the brakes,
but the engine has already returned to idle. While wondering what
happened, it revs up again - 1200-1300 O/min I think, and tries to make
another forward jump. I brake the car to a complete stop, and put the
gear in neutral. For the third time the engine revs up, and then after a
second or two returns to idle.
After that the car behaved normal, and I drove it carefully into the garage.
What could be the matter. Any suggestions?
Also I noticed once in a while that when accellerating the car - like
when overtaking other cars, it seems as if the power surges a little. Not
much, probably a passenger wouldn't notice. Could these two issues be
related?
Thanks in advance.
Erik Rudbeck
Denmark

* Driver is applying the throttle instead of the brake
* The floor mats are interfering with the throttle pedal - check to make
sure the floor mats are not touching the throttle pedal.
* The EGR system is not working properly - EGR problems are usually
related to surging while at cruising speed or very poor idle
* The idle air control valve or IAC control system is not working properly
(you can try cleaning the IAC with carburetor or throttle body cleaner
* The air conditioner idle-up circuit is not working properly
* The power steering idle-up circuit is not working properly.
--

Thanks Ray,

I'm quite confident its not the driver
I have checked the floor mat, and it is fixed to the carpet with no change
to interfere with the throttle pedal.
I will look into your other suggestions. How do I locate the IAC valve?

/ Erik

[mcbrue]

Gee! This is Great !!!!! The Lexus cars can surge their little engines
and make the cars jump ahead. So now I can see the speeding dump truck
bearing down on me in my Lexus. Fortunately I see it in time to push
the pedal to the floor and wait a while for the car to slowly move out
of the way. Then as I take my foot off the gas and apply the break to
slow donw before I hit the clas of school children who have come out
on the sidewalk to see the speeding dump trucks roar down the street,
the car surges ahead ... Hmmm ... think maybe I am beginning to
understand why the Lexus has to go in for routine service more often
than any of the true Luxury cars on the market today.

[Larry]

McBrue
You have been drinking antifreeze again. Dem ole boys in the back seat
ani't been out in a while. Couple good surges going round a sharp bend and
ya kin just sling 'um right out! They liked Jerkin Shrimp's cars better
anyhow.
Did ya move outa the trailer or did they move the bridge?

Larry
In the back yard, under the oak.

[mcbrue]

Still here under the bridge in the trailer down by the river. But I
sold the S420 and bot an LS430 06 delux model. It won't stop running
the way the S Kar did, supposedly. But it is not a true luxury car.
However, it is about a third cheaper than the S Klass, so I guess that
is what appeals to most of the owners of them. They are certainly a
touchy lot - sort of reminds me of an emporer of olden times who had a
most peculiar clothier. Problem now with tha boyz in tha bak seat iz
them is crowded in there a bit. An them just dont laik thet ole hot
rice wine nearly as much as sum gud ole beer! Sides in the summer here
it is hard to heat the saki wif out heatin tha seati. Course the seati
has them coolin thans in em, but they have no controls on the heating
or cooling amounts - reallllllly weird. You can burn your self with
the seat heaters because they keep on heating with no thermal shut
off, but so far I haven't had any trouble with frozen assets. In all
modest honesty, the coolers do not seem to work as well as the heaters
- some problems with pressure shutting off the flow of air right where
it is needed, and not really being cool enough. Oh well - there will
now be a rash of comments telling me to sell it if I hate it so much,
etc. Enjoy the Oak! Have been watching the spreading leaves for a
while in here.

[St. John Smythe]

Post by mcbrue
Sides in the summer here
it is hard to heat the saki

Lexus owners shouldn't have to heat their sake. Heating is for mediocre
sake. High-quality sake is served cold.

[Ray O]

Post by Erik Rudbeck

Post by Ray O

Post by Erik Rudbeck
2000 LS400
Today when driving into my driveway - about 20 yards - and slightly
downhill so I enter with the brakes on a bit, the engine suddently revs
up, and the car jumps forward 2-3 yards. I immediately apply the brakes,
but the engine has already returned to idle. While wondering what
happened, it revs up again - 1200-1300 O/min I think, and tries to make
another forward jump. I brake the car to a complete stop, and put the
gear in neutral. For the third time the engine revs up, and then after a
second or two returns to idle.
After that the car behaved normal, and I drove it carefully into the garage.
What could be the matter. Any suggestions?
Also I noticed once in a while that when accellerating the car - like
when overtaking other cars, it seems as if the power surges a little.
Not much, probably a passenger wouldn't notice. Could these two issues
be related?
Thanks in advance.
Erik Rudbeck
Denmark

* Driver is applying the throttle instead of the brake
* The floor mats are interfering with the throttle pedal - check to make
sure the floor mats are not touching the throttle pedal.
* The EGR system is not working properly - EGR problems are usually
related to surging while at cruising speed or very poor idle
* The idle air control valve or IAC control system is not working
properly (you can try cleaning the IAC with carburetor or throttle body
cleaner
* The air conditioner idle-up circuit is not working properly
* The power steering idle-up circuit is not working properly.
--

Thanks Ray,
I'm quite confident its not the driver
I have checked the floor mat, and it is fixed to the carpet with no change
to interfere with the throttle pedal.
I will look into your other suggestions. How do I locate the IAC valve?
/ Erik

The IAC valve is usually located on the throttle body. To find the throttle
body, follow the black plastic intake tube from the air filter housing; it
should be connected to the throttle body. If you disconnected the black
plastic intake tube and look into the throttle body, there will be a
throttle plate that opens and closes on a shaft at its mid-point and is
controlled by the throttle pedal. When the throttle plate is closed, the
IAC allows some air to bypass the closed plate so that the engine can idle.
If the IAC gets gummed up, it might allow too much air, which could make the
engine surge.