Today I noticed something annoying on my 01 UL LS430, The RPM rate drops to around 500 when I set the transmission to "D" along with a slight vibration and strangely. If i change that to P, N. or even Reverse. It jumps back to 700 normally. Above numbers are while no AC/Headlights on. If i turn on the AC, the headlights or the seat heater. those 500 jumps to 700.
What I tried so far:
- Cleaned Air filter, MAF, Throttle body and those throttle upper tiny holes (dunno their name).
- Spark Plugs are brand new, didn't even reach 20.000 km yet.
- Hooked up an OBD2 comprehensive tester and it showed absolutely nothing wrong.
- Un-plugged the MAF sensor while the car is idling and it immediately shut off (Saw it somewhere, that this can determine if the MAF sensor is working or not).