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Diagnostic & Repair Tech HELP! My car is not running right. All about Natural Aspirated OEM Lexus/Toyota V8 Powertrain. Post your N/A car problems here.

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Old 09-27-2007, 11:41 PM
Bali26 Bali26 is offline
Join Date: Sep 2007
Location: Vancouver, Canada
Posts: 7
Default LS400 High fuel consumption


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 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
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Old 09-27-2007, 11:52 PM
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Lextreme Lextreme is offline
Just call me "Lex"
Join Date: Mar 2003
Location: City of Halos
Posts: 12,046

Gotta fix the PS pump before anything. Your valve seals are bad.

* 1993 SC470TT VVTi - Twin Turbo 4.7L Iron Block at work/Shine Project Body Kit
* 1995 LS520 - 5.2L Stroker with MeisterR Coil Overs and G35 19s
* 1998 GS400 - Daily Stock
* 1995 Previa - Supercharged Previa
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Old 09-28-2007, 12:44 AM
Bali26 Bali26 is offline
Join Date: Sep 2007
Location: Vancouver, Canada
Posts: 7

Thanks Lextreme,
Since I will be doing it my self, what do you think is the best way to fix it? Buy remanufactured? Used? Repair existing? Kit?

Any advice on the fuel consumption?

Thanks a lot.
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Old 09-28-2007, 04:59 AM
Deuce Deuce is offline
1st Grader
Join Date: Dec 2003
Location: Alice Springs NT Australia
Posts: 73

Could the TRAC control be activating the brakes and causing drag? I would be de-activating it to eliminate it as a possible cause.
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Old 09-28-2007, 12:59 PM
SCV8 SCV8 is offline
3rd Grader
Join Date: Jul 2003
Location: Mill Creek, WA
Posts: 375

Dirty air filter perhaps...
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Old 09-28-2007, 08:05 PM
Bali26 Bali26 is offline
Join Date: Sep 2007
Location: Vancouver, Canada
Posts: 7


Air filter is new. Today I checked out throttle body and it was very clean. MAP was also very clean not a spec of dust.

I put a blockage in the vac hose that goes from PS to intake manifold. Did I do good?

Should I try to replace the leaking seals in the power steering or just buy a refurbished one? Whats the best way to go for DIY?

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Old 09-29-2007, 07:58 PM
Cobber Cobber is offline
Join Date: Sep 2005
Location: a
Posts: 914

PS pump is pretty easy to fix yourself. The best way is to get a repair kit.

Don't block the hose from the ps to the manifold. Done bad.
Check the oil level in your transmission as well to make sure all is good there.

Check the cold start injector is switching off. The plug is at the top back of the inlet manifold and goes into the valley, Pull the plug off for a few days and check your economy.


Oh and welcome to the forum, you won't find a better place to learn about your car and engine.
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