M103 idling economy

[Rahulio1989300E]

My 300E idles at about 600 RPM in Drive...(when at 80C)

The economy gauge say, when I am at a stop light reads right about in the middle, just a tad closer to the black area....

Is this normal? What is your economy gauge reading at idle, in D gear and at operating temp?

Thanks

[Chamorro]

My dad's 300e does pretty much the same my 190e did when it was an auto; the needle hangs out about slightly (i.e. about 1/8) above the "most-economical" reading.

[danwatt]

And when you put it in neutral, the economy gets better, but the rpms increase. Now try turning the air conditioner on.

[Duke2.6]

The "economy" gage is just a vacuum gage. The left side limit of travel is 0.585 bar and the red zone begins at 0.4 bar (1 bar = 14.5 psi/29.5" Hg), so the limit is about 17" and the red zone begins at about 12".

My erstwhile '84 190E five-speed idled on the LH stop. My 2.6 doesn't quite reach the stop because it has more valve overlap (300E has the same camshaft), and it doesn't generate as much idle vacuum (16-16.5" Hg.) Never measured the 2.3 but it was probably around 18".

Reducing revs or increasing load - such as having the auto trans in drive or engagement of the A/C compressor will reduce idle vacuum.

Mercedes eliminated the gage because people didn't know how to use it and many owners were confused by it's readings. I wish they calibrated it in bar so I could read actual manifold vacuum.

Duke

[Rahulio1989300E]

Okay, so should i just ignore it?

When I put it in neutral, it does indeed make the needle pmove closer to the black area of the gauge.

I just wanted to make sure the car was running okay at idle...

so from what I understand, this is normal.....

Thanks!

[Duke2.6]

Though my car doesn't have an automatic, your readings sound normal for an automatic, so yes you can probably just ignore it. Most people do.

Duke

[mercedes rulz]

I drive a 300 ce 1989 and see the same on my Economy gauge. I assumed that since the motors running and the cars not moving thats not good economics. But once I engage and begin to move the needle moves accordingly. It always amazes me to see what speeds I can achieve with a little less pedal (and gas) and a little more patients.