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mtnickel

My Gs400 Running Weak

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Hi guys. Thought I'd come here for help first.

So I've purchased a 1998 GS400. It has about 90k miles on it. Does not burn a drop of oil. Idles smooth. Bone stock.

Here's the problem. The car seems quite sluggish and slow.

I've timed 0-60 runs with power braking at various RPMs, after resetting the ECU, etc. and the best I could ever pull was about a 7.1. Typical is lowish 7.3s (60ft's about 2.6 seconds). To me this seems unacceptable since new the car should should pretty close to a sub 6 second. Even 6.2-3 I'd be fine with, but I'm averaging a FULL second slower than that.

My g-tech dyno (actually in my iphone, but reasonable accurate) puts the horsepower at around 180whp using a 4000lbs calculation.

I already checked the ODB reader hoping to find a code (thought the car was running in a safety map/sort of like limp mode. Other cars do this if the knock sensor and or o2 sensors are bad). Unfortunately no codes were thrown :(. Though i guess that is good. haha.

I'm guessing the car just needs a decent tune up.

Can anyone think of a good place to start?

I'm leaning towards,

Spark plugs

Clean MAF sensor

New Air filter

Any other issues with these cars that can affect their performance? I'm fairly confident the compression is good. Perhaps maybe a bad VVT valve? Is there a TPS on these? It almost seems to run more responsive/powerful at 1/2-3/4 throttle. Going WOT isn't working.

If these clean-ups don't do much, i suppose my next step would be to look at purchasing a decent obd datalogger to see what's going on ignition and fuel wise. Perhaps also hook up my wideband o2 and or do a dyno run to see what it's putting down.

This was my first lexus purchase and I know the car is capable of more. Any thoughts would be appreciated!

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Side note. Flooring it gets ZERO wheelspin. I can barely get wheelspin doing a breakstand (and yes i know how to do one). It's the idle-3000rpm power that's really struggling the most. My dad's 540i by comparison is a rocket off the line.

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You should get 0-60 in about 6.1 sec.

When resetting the ECU, it needs some time to adjust for optimal settings, therefore it's not the best momentum to measure performance. No OBD codes and a 1.2 sec degrade (not too bad for a '98 car), can point to a tune-up. Do you know anything about the car's past in terms of maintenance?

So, before getting into the guessing game, go with the obvious tune-up first: clean throttlebody, replace plugs, get new filters. Perhaps 'park' the cleaning of the MAF for a moment, you wouldn't be the first to damage it in the proces.

While your at it, flush and refresh your transmission fluid too.

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Hi Guys, I have a 2000 GS400, it too, became little bit slower with time. i have check eng. light on ( bank 2 sensor 2) but it went away after awhile. I think I am loosing a compression in the engine. Any thoghts ar ideas?

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My 2000 GS at 175000 is still fast, but my wife's RX300 became very sluggish a month ago. It was the MAS airflow sensor - it just needed cleaning and the car has been much more energetic ever since. Could there be a sensor problem that's causing the ECU to detune the engine?? The RX did show a trouble code, but it was quite ambiguous.

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