2002 Ford F150 4.6l automatic, 46000miles.
My speedometer will go up and down, 15-100mph, by itself when I am idling at a light or below 10mph. When the speedometer max's at 100mph, the engine shuts off. Also, I noticed my odometer changes as if I am going the speed the speedometer shows.
I did a search on the forum and found a thread with the same poblem, where you said it was possibly a loosed ground. That doesnt sound right.
here is the original thread:
" Question: 2002 Ford F150 mileage: 140000. My truck started cutting out or stalling when in idle mode and/or when I go to release the clutch to take off. Whenever it did this the mph needle would also “wave around” as I am going down the road. If the truck took off OK and I noticed the speedometer needle would wave around, I would be forewarned about coming to a stop on an incline. This would last a day or two and then go away for 2-3 weeks and then come back to haunt me again. After 4 months of this along with going to four Ford dealers for an answer, this problem came back for good and nobody seems to know what’s going on. Finally, I went through the fuse list. Found the very last fuse that had speedometer on it, along with nothing else that pertained to my truck. Pulled this fuse, wiped out my electronic odometer along with my speedometer needle. Now my truck runs fine. Is it the speedometer sensor? That’s the only logical answer that I have heard. I’ve been there done that with spending money to replace this and that to have my vehicle not get fixed. I am looking forward to your opinion. Thanks for your time.
Answer: We do not think the problem is the speedometer sensor. Check for bad or loose ground connection to the instrument cluster.&Quot;
I'll try this one. Have you checked the sensor at the back wheels. It is located in the middle of the differential houseing on top. Also ckeck the wiring coming from that switch trase it up a ways I have seen them get rubbed by other cables and hoses and break the wire inside. This sensor controls the ABS, speedo and cruse. If speedo is jumping aroun chances are the wire is looseing contack and regaing and that makes it jump also the cruse gets it's signial from the VSS. Check these wires out close 8) NOS