Lexus LS400 surging

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.

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

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.

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.

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.

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.

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