jpdocdave

my xj tac and speedo are spiking and dropping at times. spurratic, an a 20 min drive maybe 3 or 4 times. anyone had this. if it was speedo only i'd say speed sensor. i have no add on electronics. i'm a professional mechanic, so i'm gonna cover the basics. just want to see if anyone has had this personally. i will start with grounds, but i think its weird the tac and speedo act up together and thats it. sometimes the speedo acts up alone.

thanks

jpdocdave

bueller?........bueller?........bueller?

9XJSPORT7

Hard to say what it is but ,y brother n laws 92 XJ would randomly cut out and the speedo would not work neither would the tack. We replaced everything including the computer. We ended up just unpluging the speed sensor and that solved the problem it stoped cuting out. So we replaced that and everything worked. Does it cut out and try and stall when it starts acting up? If so try unpluging the sensor and see if that makes a difference

jpdocdave

thanks man, the jeep runs perfect the whole time. the speedo will go up maybe 5 mph, and then fluctuate for just a second, and only recently once or twice they both go almost to zero and then right back, and then work fine. and sometimes the tac mirrors it, sometimes it doesn't.

could the speed sensor screw with the tac? thats the only reason i haven't just replaced the speed sensor. but if someone has had the speed sensor mess with the tac maybe thats all it is.

9XJSPORT7

The tach is not usually wired into the speedo and I don't recall if my brother n laws tach was going up or down I just know his was cutting out and the speedo was off and only worked half the time. You could still unplug it and see if the tach works or not.