# Lexus ls400 1994 **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** ls400, lexus\ **Created:** [January 30, 2012, 1:12am UTC](https://community.cartalk.com/t/lexus-ls400-1994/70687 "2012-01-30T01:12:56Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![crazylady61](https://avatars.discourse-cdn.com/v4/letter/c/ba8739/32.png) [@crazylady61](https://community.cartalk.com/u/crazylady61)\ **Post date:** [January 30, 2012, 1:12am UTC](https://community.cartalk.com/t/lexus-ls400-1994/70687/1 "2012-01-30T01:12:56Z")
My mom owns a lexis ls 400 and is having problems with it sputtering. I have been trying the Internet with no good results. She has had it "fixed " two times, which did nothing. New spark plugs and a tune up, a new fuel pump and nothings working except spending lots of $$$. Do you guys have the correct answer to this problem??? ---
**Author:** ![crazylady61](https://avatars.discourse-cdn.com/v4/letter/c/ba8739/32.png) [@crazylady61](https://community.cartalk.com/u/crazylady61)\ **Post date:** [January 30, 2012, 1:14am UTC](https://community.cartalk.com/t/lexus-ls400-1994/70687/2 "2012-01-30T01:14:25Z")
Lexus ls 400 1994 ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [January 30, 2012, 1:35am UTC](https://community.cartalk.com/t/lexus-ls400-1994/70687/3 "2012-01-30T01:35:21Z")
The problem might be with carbon deposits on the intake valves. When this happens some of the incoming fuel gets absorbed by the carbon deposits and leans out the fuel mixture going into the cylinders. This then causes the engine to run rough or sputter. You might try using a Top Tier gasoline to see if that removes the carbon deposits. If there are no gas stations that sell Top Tier gasoline in your area, then you can try adding a product such as Seafoam Engine Tune-up to gas tank to see if this helps removing the deposits. Here’s how bad carbon deposits can form on the intake valves that can cause an engine to run rough. Tester ---
**Author:** ![crazylady61](https://avatars.discourse-cdn.com/v4/letter/c/ba8739/32.png) [@crazylady61](https://community.cartalk.com/u/crazylady61)\ **Post date:** [January 30, 2012, 1:41am UTC](https://community.cartalk.com/t/lexus-ls400-1994/70687/4 "2012-01-30T01:41:21Z")
We use the highest grade fuel and it still has this problem. Will try the seafoam tho, thanks. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [January 30, 2012, 1:47am UTC](https://community.cartalk.com/t/lexus-ls400-1994/70687/5 "2012-01-30T01:47:35Z")
A higher grade fuel doesn’t contain any more detergents than a lower grade fuel unless it’s a Top Tier fuel. So don’t waste your money on a higher octane fuel unless the engine requires it. And if you use a higher octane fuel in an engine that doesn’t require it, guess what can happen? Carbon deposits can form in the engine. Tester ---
**Author:** ![crazylady61](https://avatars.discourse-cdn.com/v4/letter/c/ba8739/32.png) [@crazylady61](https://community.cartalk.com/u/crazylady61)\ **Post date:** [January 30, 2012, 1:57am UTC](https://community.cartalk.com/t/lexus-ls400-1994/70687/6 "2012-01-30T01:57:56Z")
Ok, it says premium only. Will try Shell. Thanks! Any other suggestions out there??? ---
**Author:** ![Brayvo](https://avatars.discourse-cdn.com/v4/letter/b/90db22/32.png) [@Brayvo](https://community.cartalk.com/u/Brayvo)\ **Post date:** [February 4, 2012, 10:49pm UTC](https://community.cartalk.com/t/lexus-ls400-1994/70687/7 "2012-02-04T22:49:25Z")
SeaFoam is excellent for keeping older engines clean inside. My wife and I just bought a 1991 ls400 last summer, over 200K on it. My gut feeling is that your problem is a misfire. Either a plug wire shorted to ground or a cracked distributor cap. If your car is newer it may have a coil for each individual cylinder. Same theory holds as the coil extentions to the plug will short to ground in the spark plug tube. Possible deffective coil. If all that checks OK, maybe EGR issue. Happy Motoring PS. Top Tier Gas IS Best ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [February 5, 2012, 12:26am UTC](https://community.cartalk.com/t/lexus-ls400-1994/70687/8 "2012-02-05T00:26:17Z")
There are lots and lots of suggestions that could be made. What you probably need is a good, local mechanic who will actually try to find out rather than just putting new parts on it. (Although you’re not losing with new plugs & if the fuel pump was the original you didn’t really lose there either). ---
**Author:** ![mark9207](https://avatars.discourse-cdn.com/v4/letter/m/71c47a/32.png) [@mark9207](https://community.cartalk.com/u/mark9207)\ **Post date:** [February 5, 2012, 12:27am UTC](https://community.cartalk.com/t/lexus-ls400-1994/70687/9 "2012-02-05T00:27:01Z")
Here’s a list of retailers who sell top tier gas. There is also lots of other good information on this website: [http://www.toptiergas.com/retailers.html](http://www.toptiergas.com/retailers.html)