Rpm going down the road after tach sensor replacement

[autotech84601]

I found a used new tach sensor and installed due to mine being inop since day one of owning my 89 F350. Since I've never really seen the tach work , what rpm should this idle at and what about going down the freeway at 65? I have 2857516 tires with the zf 5 speed. Any estimates are appreciated. It is a SRW as well. Thanks.

 

[vandy7.3]

What's the gear ratio?

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[autotech84601]

410 I believe according to the tag on the diff. It's the bottom row right? The door shows a 35 as far as axle id.

 

[vandy7.3]

My truck has 4:10's with a zf5 running on 265/75/16's.
I see about 2300rpm at 65 iirc, maybe 2200.
Idle is about 500-600

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[autotech84601]

Hey thanks for the info. Looks like mine is doing the exact same. I was a little worried that the rpms were higher than normal even though it has the over drive but I'll take it. What kind of mileage should I be expecting? I think I'm getting 14 with mostly freeway driving at about 60. I also think that my thermostat is stuck open as I took a temp gun reading after getting of the freeway with four miles of city driving before I checked the temp. Took the cap off and shot a 160 coolant temp. Will mileage improve with higher temps? Thanks.

 

[vandy7.3]

I see anywhere from 11-14 thats combination city hwy and light towing. You might see a little bump in mileage with the truck running at operating temp like it should.
I know the t stat was bad in my truck when I bought it, but haven't really checked mileage since I've put a new one in.
My truck has been tore apart putting a turbo on for a month now, just waiting on injectors...

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[autotech84601]

Do you think I should see more with a turbo? Have a 088 ats on it. Should this have bigger injectors? Still learning tons....

 

[vandy7.3]

If the truck runs smooth and starts good then the injectors are probably fine, im just putting new pop tested ones in mine so I know they are new. And I have other plans for more horsepower. I'm just taking one step at a time.
As far as better mpg with a turbo, perhaps a little better. But that all depends on how you use that go pedal haha

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[autotech84601]

Awesome info. I'm a granny driver, so after thermostat I hope I get a little more. Should I be using an additive for more lubricity for the injection pump and if so what recommendations or where can I read more about it? Thanks again fir dealing with the newbie!

 

[vandy7.3]

Yes you definately wanna run fuel additive. I do in every tank.
I use opti-lube XDP formula, ordered it online at 55$ a gallon and treats like 500 sum odd gallons I believe.
If you do a google search for fuel additive test you will find good info. The test I found showed the XDP formula placed second overall for lubricity behind biodiesel. I believe its better than anything you get at the local parts store.
Other people on here prefer the stanadyne additive which is good too.
But search the additive test on Google and read all about it

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[autotech84601]

Apparently optilube is located 5 miles away from my home.... lucky me! I double checked my rpms at idle and found 750.... to high? What can I do to adjust?

 

[vandy7.3]

Idk if that's too high, but it's higher than mine.
My high idle is around 900-1000. I would say 750 is alright. I've never adjusted mine so Idk how to adjust it really.
Just wait around someone will chime in with more info.
I'm fairly new to these myself but I've done plenty of research on this forum to steer you in the right direction haha

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[autotech84601]

Thanks for the all of the help... very much appreciated.

 

[89Laredo]

idle adjustment is just a screw on the throttle linkage.

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[FarmerFrank]

750 isn't too bad, I tend to like mine in the 750-800 range. They just seem so loud and "clanky" at 600-650