amoney92

I just got a 2005 v6 mustang, and there really is no problems with it, except the speedometer. When we speedometer says i'm going 60, I can tell i'm going faster for one, but my gps says i'm going 73 (which is right). And I'm wondering if anyone has any ideas about why this would be happening?




The odometer is also lying to me, Its about 1/10 of a mile slow, so when i've gone 10 miles I've really only gone 9, or 100 i've really only gone 90, which means I can't really calculate my gas milage accurately. Any ideas?

obxdude018

Ugghhh, for one I hate gps, just detest them, even though they are pretty good about getting your speed correct, possibly there was a gear change done and they never corrected the speedometer and thats why you are off.

amoney92

I'm not a gps fan either, but i ran the car for 3 miles at the same speed and the gps never changed. But assuming that a gear change were the issue, it wouldn't be a big deal to get fixed?

obxdude018

If it is that issue you would need a tuner to change the computer to adjust for that, if you just bought the car you can ask the previous owner if they changed the gears, they possibly could of returned the car to stock to keep their tuner and just forgotten to mention that to you.

Topless89GT

Tuners, different tires and wheels - changed speedo gear. Loose speedo cable.
If you bought it from an individual, I'd call him first.

amoney92

Well I bought it from a private dealer, that has his own business in Dallas. Not sure if he would know or not, Thanks for the input guys!

JimC

What size tires are on the car?

Nuke

Tire and gear changes without restting the PCM values for those will cause the speedometer to be off. You can adjust them with a handheld tuner but if you're going to spend the $$ for the tuner then it only pays to get some custom tunes and take advantage of the potential 15-20 RWHP gain with a CAI & custom tunes.