Speedometer Not Working Properly, My speedometer jumps mphs very erraticly Options

[RyBegz]

My 2000 Mitsubishi Eclipse GS has baffled the mechanics at the Mitsubishi service department at a local dealer. My car developed a problem shortly after I took it there after a regularly scheduled oil change. It was the first time I took it there because I was fed up with Pep Boys (they replaced my water pump twice in 8 months). Shortly afterwards my speedometer is unable to properly display how my normal speed. It would jump from 0mph to 60mph when I first accelerated. When I drove/drive on the expressway it jumps anywhere from 60mph to 80mph to 100mph in split second intervals. My car would also display a check engine light after the car "jolted" and locked into 3rd gear with the neutral display flashing (know its 3rd gear cause I auto-sticked shifted and saw the gear that it was locked into). I took it to the same service department and they said it was most likely the speed sensors. I waited a week to have them shipped to the dealership. The parts arrived and the head mechanic said he would replace the sensors and that a transmission flush was recommended after they replaced the sensors. I come back after a full-day (10am to 5pm) and they said the speed sensors was not the problem, that they had to call technical service out in California and that it was too late in the day to call. (first off they had all day, second isn't California a few hours behind so their department would still be open?). They said to bring the car back and they would dianosis the problem. Once again I gave the a whole day and said they still haven't figured out the problem and that they were only going to charge me $90.00 (one hour) even though the mechanic worked on it for six. The head mechanic said that it was a wiring issue and they would have to replace wire by wire, until they found the route of the problem. It could be anywhere from two hours to ten hours, he stated. I left with the mechanic giving me a very nasty look. Afterwards it worked fine, it speedometer accelerated with my actual speed instead of needing moving all around. I noticed that the mechanic took out my power adapter out of my cigarette lighter (has three different sockets and is a aftermarket product) and plugged it in. I also noticed that my fuse box cover was removed and put back. Could it have been as simple as a blown fuse. My co-worker who was a pervious mechanic said that I have a 6V fuse and that my cigarette lighter and speedometer could be linked to one fuse and to replace the fuse with a 12V and I can continue to use my power adapter (iPod adapter, radar detector). Another co-worker said it was unsafe, that the wiring could not support 12V. Now the laundry list of questions if you haven't stopped reading.

1) What is the most likely problem?
2) If it is the fuse can I replace the fuse with a 12V and not cause a hazzard while fixing my speedometer problem?
3) The head mechanic stated that he had to replace the speed sensors because that was the first possible problem the computer listed, could he have tried another means first?
4) Is a transmission flush recommended after changing a speed sensor?
5) In your opinion, was the department trying to scam me? (speed sensors, anywhere from 2 hours to 10 hours for replacing the wiring)

I would truely apperciate it if you responded to my post. I have lost some faith in Mitsubishi because of all the problems that were associated with it when I purchased it at 86k (now 118k). I just want the car to last till 200k without any significant problems and sooner or later, I'm about to give up on it, even if I'm $1500 away from paying it off. Thank you for your time and patience (long post sorry) and would be great to hear from someone.

[roughneckeyad]

Im not sure if the fuse can make a speedometer do that. But its possible, if you keep getting short circuits. First thing i thought, if the speedometer keeps jumping like that, it had to be wiring.. corroded wires or something loose. And wiring can be a nightmare and yes can take up to 10 hours, but usualy, if the mechanic is good, it shouldnt take more than 1.5 hours to figure out the problem and replace it. Second, Ur 3rd gear locked? i think thats more important than ur speedo.. it could be from 3 things, speed sensors, or computer, or ur tranny is dying. If it had to do with ur speedo, then you shouldnt worry about it much, if its ur computer, its going to take time to fix all that, and probably expensive with mitsubishi.. if its ur tranny, then flush... BUT DONT FLUSH, UNLESS UR 10000% sure that its ur tranny. Plus dont pay them for the stupid speed sensors because they havent fixed ur problem, and if u already did which i suspect u did, then have them fix the wiring and deduct the price that u paid for the sensors because obviously, it hasnt fixed ur problem. I dont think they're trying to scam you, i just think they're inexperienced.

[silver03GS]

Don't flush your transmission unless it's your absolute last option to prolong the life of your transmission. It will either help your tranny, or it will destroy it, you can have them drain and change the fluid in your transmission but DO NOT let them flush it. Cause they'll be pushing any metal shavings that are in your transmission back through it and that really can mess it up alot worse. So have them drain it not flush it.

[Aiden J]

for an electrical problem ask your co-workers, friends, and family to ask around about any shops that specialize in electrical diagnostics. if you can find a good shop in your area it shouldn't take them any longer than a few hours to figure out the problem with the speedometer. the last time i had a electrical issue like that the shop found called me and fixed the problem within 2 days. i dropped it off one day and picked it up the next and it was fixed. i paid $180.00 for the service and parts.

transmission flush, um yeah, those are a scam. the best thing to do if your transmission is locking into gear would be change the transmission fluid and your transmission fluid filter. (always change the filter when you change your transmission fluid) if that doesn't do the job your probably looking at a transmission ECU problem which might also explain the other "electrical" issue you were having. taking it into a shop that knows tons and tons about electrical issues can help diagnose what needs to be done next. that is your first mission. if they can't find out whats going on with your speedometer then your looking at a transmission issue. it could be as simple as replacing the transmission ECU, but that it not what i am saying this problem is. this is really a hands on type of issue and you need to take it to someone that knows the heck they are doing. the place you have been taking it to is obviously not the place you need to go to.

[RyBegz]

I really apperciate all of your responses. Not only were they very specific, they were posted in a short amount of time right after my post. Now I actually know what I could be dealing with thanks to all of you.

Aiden J- I never knew about mechnanics that specialize in electrical diagnostics. I will definately search the area and take it to one of those shops instead of the Mitsubishi's service deparment. I wish it was as simple as what you had done. I had the car for a little more then two years and spend $3,500.

silver03GS- Thank you for explaning the difference between a transmission flush and drain. Unfortunately, I should have consulted on this forum sooner because it was already done when the speedometer sensors were replaced. Another $172.46 down the drain.....

roughneckeyad- Now I know all the possible problems that it can be associated with my car locking into third gear. I thought they were experienced because it was specificly a Mitsubishi service department connected to a Mitsubishi dealership but again, I made another bad judgement. Unfortunately the transmission was already flushed.

I will definately consult this forum if I have another problems with my vehicle. Thank you for your input and advice, its been by far the most helpful to date. And I will keep all of you posted on this particular topic to let you know what the problem was.

[RyBegz]

I finally got the speedometer problem resolved. I gave my local dealership one last chance to fix my car by giving them two days. They didn't get started on the first day cause of the owner of the dealership had to service his car (how many mechanic's did his car need?), then they said they wouldn't get started on it till Friday and wouldn't be ready to till Monday because they are closed on the weekends.

I then got in contact with another dealership roughly 50 minutes from where I live in Turnersville, New Jersey. I drove my car up there once and they replaced damaged wiring in the "harness." It speedometer still jumped at speeds in excess of 60mph but at least the check engine light was off, so I could pass inspection. A mile away from the inspection station my car locks into 3rd gear (as previously explained in my first post) and my check engine turns on. I drove it again to the dealership and they replaced all the wiring in the whole "harness." They said the cause was either a shorting of one of the wires or a corrosion issue. Each maintence's bills in Turnersville cost $250 the first trip and $350 the next, which I considered not so bad since the speedometer's that were replaced at the other dealership exceeded the two bills total and that wasn't even the issue. I appreciate the feedback and will post another issue I have under the topic title "Stereo: Anti-theft code issue."

Ultimately I learned to never take my car back to Mitsubishi Pleasantville, NJ and to take it to Mitsubishi Turnersville, NJ, if anyone reading this post is from New Jersey.

[EMC 3000gt]

VSS

Vehicle Speed Sensor. Its something to do with that.