My gs400 lexus misfire on the driver side

Question edited for clarity.
Question moved to GS400.

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https://www.google.com/search?q=98+lexus+gs300+coolant+temperature+sensor+location

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controls ignition and any accessories that may be switched on including air con fans.

the title is contradiction
" check light on, no codes."<< totally wrong
scan it one more time with a REAL scan tool this time. (there are DTC errors , or codes as you said)

what does bad idle mean? misfiring, or idle speed too low
or too high? RPM, or
surging?

say what that means please.
and more important is engine hot or cold ? failing.???? or both????
there are over 50 causes.
but can be broken down to simple physics and gauges.
1: engine bad, lost compression.
2: engine cant breath, dirty air cleaner
3: ISC stuck closed or open or just stuck. (bad idle air supply)
4: bad spark, 1 or all 4 (never had a tune in this decade.
5: cam drive, slipped (belt) causing #1 failure.
6: air fuel mix too lean, and causes rpm drop and ISC fails.
7: air fuel mix too rich and misfires.
8: egr stuck open, it misfires and ISC gives up.
9: cat clogged, engine cant breath #2 like.
10: and the vast other reasons for misfire.

we cant drive it, see it or hear it misfire, so.....????

there is a test for all 10, ask. or get car serviced.

Did you ever figured it out on the GS400?

On this website, you find fuse box diagram and description for Lexus GS400 (1998 - 2000)

Lexus GS400 1998 2000 fuse box diagram Auto Genius

Check Engine Light On, P030x Specific-Cylinder Misfire Code A cylinder specific misfire indicates that either compression, appropriate fuel mixture, or spark is missing. Start with a visual inspection, looking for a vacuum leak near the cylinder and any sign of wear on the spark plug wire. Check the compression on the target cylinder to ensure that the engine is mechanically sound. Use a stethoscope to listen to the suspect cylinder's fuel injector. Listen for distinctive clicks and compare to another cylinder.

means u have a misfire on cylinder number 5. whens the last time u changed ur spark plugs?

You describe a 'Misfire' condition. You'll need and OBD!! scanner to retireve any throuble codes stored in the ECU (Engine Control Unit). Once you know which/what code (i.e., P0300 - Random Misfire Detected, or P0302 - Cylinder #2 misfire detected, etc). then you'll know where to go from there - plugs, wires, coil(s), etc.

For 1999 Lexus GS400 4.0L SFI DOHC 8cyl the Flasher is located front seating area, driver side, behind instrument panel, mounted on upper corner of dash.

Hope helps. (remember rated and comment this).

i have a 98 lexus gs400 my battery light came on......do i have to replace my alternator?