CLSinner

Hey there,

New to all this but I recently purchased a 2000 LS400 with about 166k miles. Drove around fine when I bought it then started to notice some stuff wonky on the drive home. When I was sitting at a light I quit getting power when I put my foot down and it started idling terribly, then shut off. Keep in mind when I'm not stuck at a light or am just parked before the issue appears she runs like a top. Got it to start and got home and replaced the MAF, which seemed to fix almost all of the problems I noticed. Then I drive it to work this morning and while putzing around town it does this again at a light so I pull into a nearby lot and eventually give up trying to get it going since I have to be at work. All my research points to the IACV thus far but I tried to find it when I changed the MAF to no avail. Any assistance would be greatly appreciated

Yamae

1998 and newer LS400 do not have IACV.
https://www.clublexus.com/forums/ls-...l#post10351300

CLSinner

Thanks for the quick response! I see that people generally point to ECU or throttle valve, possibly gunked up or damaged injectors. I have a worry that they weren't using premium gas but I am not sure, I'm going to get some octane booster and fuel treatment and run through the gas in the tank if I can get it going long enough, and perhaps changing vacuum lines. Is there any other course of action you would recommend outside of this or replacing the ECU?

Fit1too

If you don't have a check engine light on and/or any codes to guide you, I'd look at vacuum lines and cleaning the throttle body, including the air mix path. The search feature will yield many results to help you with most anything you have going on.

Legender

Definitely check the throttle bottle and butterfly for being clean. When warming up it's open slightly more thus seeming to be OK, but when warm it will close down more and if gunked up may be restricting air flow. Also insure throttle linkage cable has correct slack.

Fit1too

Read this before you dive into the ECU: https://www.clublexus.com/forums/ls-...capacitor.html



If the car sat a lot before you got it, it might just need to be driven for a while. Remove the top engine cover and study your vacuum lines. Also, look for loose connections and what not. The previous owner may have had it worked on just before you got it, and something is loose. Start with the simple things. Using quality gas is a must for all cars and our vehicles do recommend Premium fuel. I've seen on the forum were others have commented on using mid or low octane fuel, but no matter what you use don't get it from the station out in the country that has been there 50 years and have never changed their underground storage tanks. And don't get gas when the tanker truck is filling up the underground tanks! I use Top Tier Fuel i.e. Shell, Chevron, Exxon, etc. Here in Indiana we have Country Mark stations which use regional American sourced oil from the Illinois Basin—and is considered Top Tier fuel. It is available in surrounding states as well. Another thought—it could be old gas in the tank and/or water (from sitting, condensation etc.) Seafoam would help with water. I have used Red Line SI-1 Complete Fuel System Cleaner without any negative results to clean the system.

Yamae

You might already have searched out this page below but I dare inform you to understand how important to clean 2 air mix passages.
https://www.clublexus.com/forums/ls-...ml#post8906720

CLSinner

Thank you all very much for the input! Going to work, collecting supplies, and getting around town without a vehicle the past couple days has left me without a lot of time to mess with it. When I get out today the rest of my weekend is dedicated to her, and I'll get back to you all before long I'm sure!