[axepert]

When in Neutral, my car's RPM is at 750. When engaged
in "D", it drops to 500 and the car vibrates pretty
badly. Should I ask my mechanic to increase the RPM to
reduce the vibration ? Will this increase the car's
petrol consumption ?

Is there a recommended RPM setting for auto cars ?

[Fuhrer]

this is probably a tuning question. your tuning my be
out..
most car manuals usually tell u at what rpm the car
should idle at. also with a timing light, u can tune
your car to acheieve the recomended timing.
i don't like it & usually tune it up a notch higher to
achieve greater performance. does make a difference in
terms of greater pick up.
i notice it when my mech changed my plug cables &
retuned the car. drove it home & i didn't feel the
same response as i did before...so had it tuned again..
but by doing so, it does somehow consume a little more
fuel..but its well worth it! ; )

[axepert]

Thanks for that Fuhrer. Will check with my mechanic ..

[MASsenger]

axepert, if U are still having the same problem here is some information.

The right idle RPM for an engine will be quoted in the service manual. When 'D` is selected ( auto gearbox ), there will be a slight drop in RPM. This is due to the on load situation. When the car is in `N', there is no load on the engine. As soon as `D' is selected the engine is on load, hence the slight drop in RPM. However an automatic RPM compensator increases the RPM slightly, so that the engine is at it`s best idle speed.

Now since U are not getting this increase in RPM upon gear selection, I would say the automatic compensator is faulty. This is not a big problem, but may be a bit expensive to fix, depending on the make of the car. The quick fix ( and I am not sure if it is cheaper ) is to increase the off load RPM slightly. Now when U engage gear, the drop in RPM will not cause the vibrations. Bear in mind this quick fix does increase fuel consumption.

[anthonywyc]

500 is too low lah...

[g88]

Engine shaking badly and RPM drop till 500 when in "D"....possibility is time to change engine mounting. Alternative might be ECU or tuning problem as been mentioned.

Hope my information help you

[axepert]

Yup, have checked with my mechanic and confirmed that the engine mountings are worn ... thanks anyway guys !

[anthonywyc]

Check your timing also ??

[axepert]

Well, my mech said that since my engine is running on carburetor, the timing can't be raised otherwise it will consume extra petrol ..