Hi Everyone,
I just became the owner of my third Ford vehicle a 1994 Explorer Sport. I also have a 1960 F100 and a 1980 F250, both undergoing engine replacements (too many projects).

The Explorer is a 4.0L 4x4 Sport manual transmission. My tachometer seems to stick just above 2000 rpm until the engine is revved and it drops down to 0 briefly then jumps back to 2000. On occasion it will suddenly begin to work normally but only for a brief time.

The speedometer seems to be reading fast. I did 60mph by the speedo and clocked three consecutive mile markers on the highway and came in at 57 seconds per mile. Granted that is not off by much but when I get the car up to 70mph or so I am passing traffic left and right that is generally doing 75+ so I suspect the difference is incremental based on my own speed and not just a couple miles an hour out of whack.
I wonder if possibly the tranny was replaced in the past and it has the wrong speedo gear.

I have only had this for a couple days and have no shop manuals for it yet.
Is the tach directly driven by a signal from the coil? Is this a single coil setup in 94? I assume the speedo is cable driven from the tranny.

Since this is a manual transmission is there a tach sensor that needs to be replaced or should I look at electrical connections to the coil? No idea how this beast is wired up yet.

Thanks.

 

On the 94, the speedometer is still driven by a mechanical cable even though there is an electronic speed sensor on the same assembly. Tou can trace the cable to the sensor on the back of the transfer case. One nut removes the sensor and there is a plastic gear that can be removed. This may have been changed to correct the speed or you now have larger tires. I would check the odometer first. If it is correct then the speedometer is off. You can get different teeth from 16 to 21. Each tooth larger drops the speed about 5%. If you went from 19 to 21 for example, it would frop the speed about 10%. Gears are about $7.50 from the dealer.

 

When I clocked by mile marker I came just under one mile on the odometer just as the the time came in at 57 seconds instead of 60.
I just put new tires on it and confirmed the tire was the correct size as that was my first suspicion. I know some 94 Ford products used electronic speedometers and was hoping the solution to both problems would be as simple as a sensor.

It sounds like I have two separate problems then eh?

A couple years back someone on this site gave me the formula for calculating the correct number spline speedo gear when I was working on my 60 F100. I cannot find it now though.
It involved clocking time at a set speed between mile markers then applying that number in an equation that told how many splines you needed to adjust to for the gear.

Anybody familiar with this?

Does the tachometer behavior sound like just a sensor problem or a bad tach? It kicks in once in a while for short periods then drops out again staying at about 2100rpm.

Thanks for the response.