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Power Loss When Warm


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Hi all

just really looking for a consensus of opinion. I have a 1997 LS400 Auto with 280k on the clock, its been well serviced upto 220k by lexus since then it appears servicing was neglected. I'm slowly rectifying all the problems but this one puzzles me a bit. When cold the car has plenty of power and changes nicely through the box and even for a while when the engine has reached working temperature it's ok but once really warmed up the car doesn't really fly until it has got over 2500 rpm or so. When accelerating moderately so not requiring kick down you can feel the car "surging" for want of a better word. At first i thought it was an engine issue so replaced air filter and thoroughly cleaned TB but not an awful lot of difference, so I'm now thinking maybe the ATF is in desperate need of a change, has anybody done a fluid change and noticed dramatic difference? I'm happy to do a flush of the ATF following the procedure on the site but just wondered what others think.


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  • 2 weeks later...

Hi wylie eyed,

I will be interested in seeing the replies here as mine suffers from the same problem, More noticable first thing on a cold morning the car drives like a race car "wants to really get up and go" then later on can be a lazy sort of drive, the car does not want to be rushed.

Hope we find the problem!


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Have you checked the ATF it should be a dark cherry red if good and tends to change to a brown sludge colour when it's shot.

Also have a smell of the fluid on the dipstick to determine if it smells burnt.

The problem sounds temperature related so I would also check the coolant temperature sender unit and its wiring could be giving false readings to the ECU which in turn is making adjustments to fuel trim for a cold engine when it is in fact warmed up.

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