The tachometer on my Lexus GS300 1st gen (1995) shows ~2k RPM when driving 60-70mph with the released accelerator pedal. Is that a good RPM? The engine, 2JZ-GE, I think, has 6 cylinders. Automatic transmission. 250k miles driven. Tires/wheels P215/60R16 94V.
The idle speed, according to the manual, is 700 +-50 RPM. The actual idling speed is in range between 700 and 1000 RPM.
Engine size really doesn’t play any major part in this scenario and it’s normal to stay at a higher rpm because the transmission is engaged and it’s all based off of gear ratios. If your cars in gear and your moving then your vehicle is not idling just because your foot is off the gas
My understanding is that idling happens only when the automatic transmission is in Park or Neutral. Also I though that when I release the gas pedal while transmission is in Drive, the air stops flowing into the intake manifold, and the RPM should be around idle RPM. Does the car electronically control the throttle body or the idle air valve with the foot off the gas pedal?
It does and it will only be at an idle rpm when stationary . If your driving down the highway there is still a load on the engine and the engine is still mechanically connected to the transmission and the transmission is rotating at highway speed in turn it is rotating the crank depending on gear ratio more than idle speed because the vehicle is not idling at that point
Also no matter what gear your in throttle closed or not air never stops going into the intake.. if it did the engine would stall
Thank you for your answers. This is really helpful!
You may need to clean the throttle body. I don't think it is normal that you get 70 mph with foot off the gas pedal.
I get 70 mph with my foot on the gas pedal. With foot off the pedal, the car continues to drive 70 mph for a while (for example, when going downhill), and it's about 2k RPM, and the transmission is in the Drive (last - 4th - gear).
With foot on the gas pedal, it's about 2.5k-3k RPM when going about 70mph.
Downhill is completely different game.
2k rpms at 70 in a v6 is about right. It's going to be different for every vehicle. 4 cylinder cars rev higher @ 70mph generally around 2.5k +/-, v8's will be lower. For example my Camaro SS revs about 1,600 at 70.
