Ls400 Bad Fuel Economy

[Dhillon]

Hi,

I'm a new owner of a 91 LS400 in large part due to this forum. I'm very happy with it so far. There are some things that the car needs done but I just don't have the money to have a lot done, I can barely afford gas. I prefer to buy tools than pay a mechanic. Here are my questions:

Biggest problem: The car's giving me only 13 mpg (6 km/l) in city. Tyre preasure is maxed out 38 psi but it feels like i'm pulling a trailer. Using 91 octane. What do you think is wrong? Check engine light is ok. Can the Oxy sensors be bad and not show up in check engine? How do I find out if they are bad? I have ramps and can buy oxy sensor socket. All four may need to be replaced? Or front more important than rear? What else can i do to decrease consumption? Alternator?

Other problems:

TRAC light comes on after a couple minutes of driving and periodic humming sound. Is it ok to ignore it?

Very Minor oil leak around oil pan, PS rack area. Oil level stays high.

Very minor oil leak around PS pump, area barely moist. Oil level stays high... ok to ignore?

Sometimes car blows white smoke when started. Not always.

Upper control arm joint a little loose. little play. Ok to ignore for now?

Your advice is much appreciated

[pishta]

Hi,

I'm a new owner of a 91 LS400 in large part due to this forum. I'm very happy with it so far. There are some things that the car needs done but I just don't have the money to have a lot done, I can barely afford gas. I prefer to buy tools than pay a mechanic. Here are my questions:

Biggest problem: The car's giving me only 13 mpg (6 km/l) in city. Tyre preasure is maxed out 38 psi but it feels like i'm pulling a trailer. Using 91 octane. What do you think is wrong? Check engine light is ok. Can the Oxy sensors be bad and not show up in check engine? How do I find out if they are bad? I have ramps and can buy oxy sensor socket. All four may need to be replaced? Or front more important than rear? What else can i do to decrease consumption? Alternator?

Other problems:

TRAC light comes on after a couple minutes of driving and periodic humming sound. Is it ok to ignore it?

Very Minor oil leak around oil pan, PS rack area. Oil level stays high.

Very minor oil leak around PS pump, area barely moist. Oil level stays high... ok to ignore?

Sometimes car blows white smoke when started. Not always.

Upper control arm joint a little loose. little play. Ok to ignore for now?

Your advice is much appreciated

The UCA joint has been bad on my car since its 63000M check up and Im now on 94 (bought at 93k) itll just get annoying making a racket over the smallest bumps. O2 sensors will throw a code if any are bad. You can change them, but I dont think they will make much difference. I would get the injectors cleaned, with 2 or 3 tanks of cleaner and then proffessionally if that doesnt help any. And of course, replace the air cleaner. Bad mileage can also be attributed to a clogged catalytic converter, they usually have a lifespan of about 7 years. White smoke on start means valve guides, expensive and not really a motor killer, just a nuisance. Dont know about TRAC light. Do you all have a product called SeaFoam over there? Its a multi-purpose highly refined oil (naptha I think) that you put in the tank, in the oil and in the intake. Its supposed to clean the sludge out of the oil (change after a few days) condition the gas and clean the injectors, and mostly, clean the intake valves and combustion chambers. You suck 4 oz. into your intake by the power brake vacuum hose, turn off for 5-10 minutes, and then start it up to a fast idle. Itll blow smoke like a rocket taking off, but then itll mellow out. People swear by it for reducing knock, off idle stumble and crappy idle. A little oil on the motor is not going to hurt anything, just keep your fluids topped off and dont let it become a hazard. Good luck.

[Dhillon]

Thanks for taking the time Pishta,

I was begining to lose hope of getting a reply. No Seafoam here. I will try some other fuel injector cleaner.I will try to buy a rebuild kit for PS pump and fix it myself. There was a code 24 stored but the CE light is not on. TRAC give code 19 and 51.