1Uz-Fe Rough Idling And Shutting Off When Engine Is Warm (At Half Temp

[MattLS400]

Good day folks, after having executed a Diagnostic on my 1996 LS400 with a 1UZ-FE engine, no trouble codes are appearing.


FIRST START on a morning (engine is cold) --- The vehicle works beastly perfect in traffic and on highway. No smoke, no rough idling. Normal Idle at 500 RPM

After 20 minutes (when the engine is warm) ----The vehicle begins to rough idle. No smoke.
------------------------------------------------------------When in traffic, it rough idles and the RPM drops below 500RPM and consequently cuts off. UNLESS while in traffic, I put the vehicle in Neutral and Accelerate\ REV till the Tachometer needle reaches at least the 2000RPM mark then I release the acceleration, only then the rough idle stops and idles normally again at 500RPM….and I work it like this “coasting” in traffic. However, if I drive in traffic accelerating under 2000RPM, the rough idle and shutting off would persist.
-------------------------------------------------------------When driving on highway (80 mph and more) which is above 2000 RPM on the Tachometer, the vehicle does not rough idle, it runs smooth. However, If I am driving slowly on the highway (approximately below the 2000RPM) the rough idle and jerking would persist.



POINTS TO NOTE
Mileage-- 120, 000, and stopped there since,
The Speed-O-Meter has stopped working.
The temperature never reaches above half level, it’s always either half or below the half level.

I have changed the following;

all 8 injectors to new injectors 23250-50020
Oil
Engine Crankshaft Sensor changed to new DENSO 90919-05002
Fuel Filter inside of the fuel-tank to new 23300-50060
8 Spark Plugs changed to Platinum DENSO Spark Plugs
Engine Coolant Temperature Sensor
2 Ignition Coils
Fuel Pump inside of the Gas Tank
jumper wire or "direct" run from terminals 3 and 4 in the fuel pump relay

ECU- Capacitors changed and board fully inspected

Nonetheless the problem still persists. Any assistance would be more than greatly appreciated.