Tach movement?
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From: Maryland
Tach movement?
I was wondering if it is normal for the tach to show movement while at idle. The movement is steady and very slight, you have to really stare at the gauge to see it move. But, I can also hear a very subtle rev when the tach moves. It moves approx. every 2 seconds.
Is this a problem or something normal? The truck runs great???
Thanks,
Mike
Is this a problem or something normal? The truck runs great???
Thanks,
Mike
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From: West Texas
Tach movement?
you had me a little worried at first when you said that you really have to stare at the tach before you notice it.....Wow, could that get old quick!.... I haven't ever noticed my 00 Crew Cab do it, but I will sure keep a look out for it now!
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From: NorCal
Tach movement?
Mine does it too, very slightly. I figure it's because the engine cannot idle at a perfect steady RPM. If you run the diag with the odometer you can watch it constantly changing.
My do*ge cummins at work moves alot!
My do*ge cummins at work moves alot!
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From: Baileyton, TN
Tach movement?
So, Why were you staring fixedly at the tacho, to notice it moved? 
Now you have brought this up, I have to go sit in my truck, and stare like an idiot at a barely moving needle.... Thanks!
Theo
Now you have brought this up, I have to go sit in my truck, and stare like an idiot at a barely moving needle.... Thanks!
Theo
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From: NorCal
Tach movement?
I'm surprised it moves at all, seeing how the oil gauge never moves, the volt meter never moves, and the temp can stay right at the middle no matter how hot it is while driving up a hill, fully loaded with the A/C on ... 
go figure...
go figure...
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Joined: Jun 2003
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From: AZ
Tach movement?
Does it make like a sligh click and change tone of sound when it does this?
If so, mine too.
If so, mine too.
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Senior User
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From: Maryland
Tach movement?
Hey Guys,
Sorry to get you guys looking at your gauges, but I had to ask just to make sure my truck was acting normal. It does not make a slight click prior to the rev though. But alot of vehicles do that as well. especially with the A/C on.
Don't stare too much!
Mike
Sorry to get you guys looking at your gauges, but I had to ask just to make sure my truck was acting normal. It does not make a slight click prior to the rev though. But alot of vehicles do that as well. especially with the A/C on.
Don't stare too much!
Mike
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From: Baileyton, TN
Tach movement?
OK.. I spent time in a snarl up of traffic in Memphis with my eyes glued to the tachometer....
I do not doubt that the persons surrounding me were amused at the sight of me straining down to check on it, however, that is incidental to the point in hand.
YES, my needle does indeed twitch ever so slightly, in a semi rhythmic fashion. The movement is minuscule, but definite, so now I know.. I do not have to do this anymore, so I am happy. I hope you are happy too.
Analysis:
Outside temp - 98º F
Engine temp normal
Transmission temp normal
Engine revs - 650 rpm
Voltage - 13.4 v
Air conditioning on, not cycling at the time
Fan running on medium setting
Radio on
Scanner on
Theo
I do not doubt that the persons surrounding me were amused at the sight of me straining down to check on it, however, that is incidental to the point in hand.
YES, my needle does indeed twitch ever so slightly, in a semi rhythmic fashion. The movement is minuscule, but definite, so now I know.. I do not have to do this anymore, so I am happy. I hope you are happy too.
Analysis:
Outside temp - 98º F
Engine temp normal
Transmission temp normal
Engine revs - 650 rpm
Voltage - 13.4 v
Air conditioning on, not cycling at the time
Fan running on medium setting
Radio on
Scanner on
Theo
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From: Baileyton, TN
Tach movement?
Originally posted by cgl
I'm surprised it moves at all, seeing how the oil gauge never moves, the volt meter never moves, and the temp can stay right at the middle no matter how hot it is while driving up a hill, fully loaded with the A/C on ... go figure...
I'm surprised it moves at all, seeing how the oil gauge never moves, the volt meter never moves, and the temp can stay right at the middle no matter how hot it is while driving up a hill, fully loaded with the A/C on ...
go figure...
The oil guage is a Ford favorite - it is not a gauge, it is a switched display. It can't move.
The volt meter is real, and does let you know if anything is wrong.
The temp gauge is real too - I have seen it up in the red once on my truck, on a hill, towing on a hot day in the mountains. Maybe your idea of fully loaded is not the trucks idea of fully loaded.
Theo
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From: Baileyton, TN
Tach movement?
If you notice in my post on the movement of the tach where I pointed out the AC was not cycling.. That gives a very noticable difference in idle speed and sound. This almost imperceptible movement is not that at all.
Theo
Theo
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From: Western MD
Tach movement?
Actually, with computer controlled injection systems today, the computer is actually measuring and controlling engine speed at idle. So this is a typical feedback control loop - when speed drops a little, the computer commands a little more fuel, when speed goes up, the computer commands a little less fuel. There will always be some slight oscillations around the idle speed even with no loads (fan, A/C, etc) on the engine. We see it all the time here in the engine lab at Mack.
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