Is it a wiring problem or sensor problem? - Ford Mustang Forum
 
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post #1 of 6 (permalink) Old 08-06-2011 Thread Starter
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Unhappy Is it a wiring problem or sensor problem?

hello fellow mustang lovers, im a new member so i dont know much about the site. 18 and just got my first stang, 2000 gt though sadly its an automatic but still a pretty bad stang! The only problem is somethings wrong with the speedometer and gas gauge. I could be going 60mph and the speedo will read 30mph. My gas gauge is also off too and stops at a quarter tank. What is the problem? A guy at ford said the diagnostic test would be $90 though wouldnt want to get the test if i knew what was truly wrong.Though the stang doesnt have the stock cluster gauge, but an after market one. Just trying to find some advice from other stang owners.


1989 LX 5-speed, Pacesetter shorty headers, o/r h-pipe, flow 40's, 3.73 gears, CAI, hurst shifter, daily driver
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post #2 of 6 (permalink) Old 08-06-2011
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The reason they want to charge 90$ is because that's an hour labor and for most electrical diag that is what they start at. They'll have to see how many ohms the fuel sending unit is putting out and if that reading is good and the wiring to your cluster is good it's most likely the cluster but there is no way to be positive with out testing.

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post #3 of 6 (permalink) Old 08-06-2011
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Is the speedometer in error all of the time? Need to know how much is it off.

Set the cruise control with traffic. Record the what the speedometer says. Time how long it takes to go a mile on the expressway. The mile markers are perfect for this.

Now you get to have a real world example of those math problems everyone hated in school.

It would also be nice to know if the prior owner has swapped transmissions. My gut tells me this is the case.

If this were a rear end ratio change, say for example 4.10's used instead of 3.27's, the speedometer would read higher than true speed.

If asked to handicap this thread, I would say the prior owner used a transmission from a 04 MY which has a different number of teeth on the OSS reluctor wheel. If true, this can be corrected with a tune.

But what we have to know if an older transmission was used.

Additional helpful information is to know what the PCM "thinks" the car's speed is. This will require an ODB2 scanner that is capable of accessing operational data.

Pictures af the transmission tail shaft would be a great place to start.

As for the gas gauge, my bet is the sending unit was damaged during a fuel pump upgrade/repair. Are you willing/able to drop the fuel tank if need be?

2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.
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post #4 of 6 (permalink) Old 08-06-2011
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someone mightve ****** up the needle positions, similar to another thread i just read. if its an aftermarket guage overlay, i think it's quite possible.

see the calibrating guages thread... or use the search function
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post #5 of 6 (permalink) Old 08-06-2011
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post #6 of 6 (permalink) Old 08-06-2011
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Rabbit, good point. What I was trying to do is find out if it's off by a fixed amount or a fixed percentage. In retrospect, I should have asked for the test to be run at different speeds.

Or even better to cross check the PCM speed with the speedometer.

If it's a needle issue, the difference would be a fix amount.

If it's an electronics or calibration issue, the error amount would be a fixed percentage.

2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.
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