Crazy speedo, & CEL goes on, & off HELP!

[Jason94sport]

I drove my X to NYC, from FL, some 1200 miles. After about 800-900 miles of straight driving I began to have a problem. I had my cruise set at 70. All of a sudden my Check Engine light went on, then went off, then went on & off for the next few hours. The speedo also was jumping up & down the whole time. Like I would be going 65, & it would jump to 55, back to 65 then 70 then back to 65 etc etc. The truck wasn't going any faster or slower though. My Tach was also not moving as this happend. It was steady at about 2200 rpm in 5th gear. It also happend with the cruise off. When I got to NYC, & was driving around regular streets shifting gears, the truck was fine. No CEL, or erratic speedo. I also drove a few miles on a local HW, & also had no problems. It concerns me though., because I have to drive the X back to FL next week. Speed sensor comes to my mind, but it would happend all the time. Any ideas what it could be?? I have about 64K miles, & I have replaced most of the sensors months ago, & never had a problem like this.

 

[TPLYNCH]

Speedo gear may be going. As for the CEL, unless it was happening at the same time as the speedo jumps, I doubt they're related. CEL probably an O2 sensor going off. Extended driving may have heated them up too much and they threw a code..... My Escort has done that, especially during the summer. Cruise at a steady speed, CEL comes on. But if I take my foot of the gas and let the engine coast for a few seconds, it turns off. Been doing it for years. Have not had any trouble.

 

[Jason94sport]

It was happing at the same time. So far it has stopped. I don't have access to a code scanner. I have a good one at home, so I don't see the need to buy one locally in NY just for this. I guess I will have to see what happens when I drive the 1200 miles back to FL.