First Road Trip, a Couple of Issues

In general, you will find that nearly every new car will deliberately over-read compared to actual speed as it has ramifications for speeding offences if it under-read.

Thanks for the advice.

I understand that. My 96 Cobra was dead on. If this one was just a MPH or two off all the way up I could live with it. What I am not comfortable with is that the faster the speed the greater the error. By the time i'm at 70 mph, the speedo is off by over 5 mph.

Stay alert, stay alive.

You clearly have 2 separate problems.

1)From my understanding you have both the factory wheels and gears on the car. The easiest way to see if it's ford's problem is to return the vehicle to factory tune first and retest.

The Spedometer issue is most likely caused by your X-Cal II. Is it possible that the incorrect revolutions per mile is set in your tire diameter? With all the speed sensors in this car it's virtually impossible to have any inaccuracy more than 1% since everything turns at certain ratios unless it's a software error. If you bring it to ford they'll reflash it and you'll lose your tune.

2)There have been many people with the dreaded wet passenger floor problem. The problem is more than a simple wet carpet. In the passenger kick panel there is a 2nd fuse box called a Smart Junction Box or SJB. In other cases the SJB was getting wet and shorting out causing major problems. That one I'd get done by the dealer for sure.

http://www.modularfords.com/forums/2005-mustang/need-some-help-guys-40900.html?highlight=water+leak#post418909

http://www.modularfords.com/forums/2005-mustang/weird-electrical-problem-53430.html?highlight=water+leak

Best of luck and let us know how it goes.

Thanks thump_rrr. The speedo problem existed with the factory tune. I've checked the SCT-X and the tire rotation is set to stock. With the axle ratio set to either stock or 3.55 the odometer is dead on. I spoke to Brent at Brenspeed about it and he thought that it might need a reflash, so I'll have the dealer take a look at it when the car goes in this week for an oil change and to get looked at for the water leak. As for the water leak, I plan to pull the cowl cover today just to get an idea of what things look like under there.

Sending you a PM on this.

Thank you

Thank you both for the job you do for us in the USA. Make sure you bring you butt back safe and ready to rock in the Stang. We cant thank you enough gents.

Gary & Linda Johnson

And THANK YOU for your support!

MarineOne -

The water leak could be a bigger problem. I have been following this issue on a couple of other forums.

I would suggest that you pull your passenger footwell fuse box cover. Probe down below until you can feel under the carpet pad. Is it wet? I have read that some owners have mold growing under there.

I have also read that there is a grommet on the passenger side of the firewall that allows wires to pass through the firewall into the back of the dash. Some say this grommet area is the problem.

Good luck with the problem, and stay safe out there.

I would verify it with something other than the Garmin just to make sure. I have used a handheld Garmin GPS in a few cars when I was the passenger and it always seems to read lower than the car speedometers. It's probably the speedometers that are off. I never tried it in my mustang (I'm never the passenger in it). A Toyota camry and a Ford Focus both read higher speeds on the speedometers than the GPS did.