teemotang

So I bought my V6 '05 Mustang a month ago, and I noticed a few days later that I seemed to be doing 80mph when it felt I was doing 55ish. Sure enough, I stop and my speedometer reads 25 mph. I cut the engine off and turn the switch all the way off. I turn the switch back on, it reads 25 mph, I crank the engine and it moves back to 20mpg. I cut the engine off, turn it back on and after I crank the engine, it moves back another 5 mph. I do this until it moves to 0 and then it's normal. A few days later, for no reason that I can tell, it reads wrong again, maybe only 10 mph over this time, it's erratic. But it always moves up, then after cranking moves down 5 mph.

A few days after I noticed the speedometer doing this, I had my oil changed. A mile down the road from leaving the oil change place, I see my temp is buried in the red. I pull over, check my fluids and actual heat and it's still cold (drove less than a mile to the oil change place, then another mile after they changed the oil). I call the Ford place, they say probably bad instrument cluster. I go and test, and sure enough it's the same thing, after I crank the engine, it moves back a little bit. I turn the car off and re-crank it about 8 times and each time it moves back to normal a little bit until it's correct. The other gauges I have saw no problems with, mostly the speedometer but sometimes the temp gauge also.

What is this? Anything I can do? Any help appreciated!!!

Avalanch3

Does your car have a tuner on it? Have you tried disconnecting the battery/reflashing your ECU?

157dB

The insturment cluster gets its dats via a high speed can buss.
It could be a bad cluster (must be replaced, cant be repaired)
or its a faulty speep sensor or a bad PCM.
Have there been any OBD codes thrown?

BigGameHunter589

i have the same thing temp gauge wise.. I'm not exactly sure what to do either so I've just been living with it

teemotang

Avalanch3, no tuner that I know of. How would I flash the ECU? I'm not a mechanic, is it something a layperson can do?

157db, if it was throwing ODB codes where would I see them? Or are you talking about it being tested with something? What is a PCM? Is there any way to test which of those could be the problem?

Once, the speedometer just simply stayed at zero when I drove. But mostly it will work just fine, then all of a sudden it will read 5-30 miles per hour more than I'm driving and stay that way (not bouncing, if I'm going 30 it'll read 50 and if I slow to 10 it'll read 30 etc. If I stop it'll read 20) until I cut it off. Each time I crank (something happens when it cranks that makes it move back a little) the car it will move back 5mph.

Obviously, the dealership will charge an arm and a leg to replace the instrument cluster, on top of them being over $300 at a dealership. I have found a 6 gauge cluster, but not sure if it will work with my car as it has 4 gauges. From what I've read some will and some won't.

Someone had said to reset the computer, is that reflashing the ECU? If so, should I do that and how would I?

Thanks for helping me I really appreciate it.

157dB

You could see the codes with a tuner, a MSD dashawk or similar item.
PCM = Powertrain Control Module or the ECU whichever you prefer
calling it.

You can put the 6 guage cluster in there but it will need to
be loaded with the proper 'as built' data. The Stealership
will have to have a hand in the 4 to 6 guage swap.
The insturment cluster is replaced as an assembly and
if you had DiagnosticTroubleCodes set and could read
them it would be easier to diagnose the problem via
an internet forum.

Avalanch3

Don't know if this will work or not, but it is worth a try: Disconnect the battery for about 15-20 min then load it back on.

Don't know if it will help your problem here, seems like the instrument cluster to me. If anyone else can chime in on this, that would be better.

BWfVA

Well my Speedo seems to something of the same thing you are talking about, such as in it seems to roam around some, like one day it will 5MPH off slow and the next time I will check it, it will be off by almost 10MPH slow but it never reads like yours when you cut it off. I have just been dealing with it cause I really dont know what else to do. My compter is completely stock

teemotang

Thanks everyone, I have found a used cluster and will try that. I know from reading forums (thanks by the way!) how to take it all apart to get to the cluster, and have done so to mine. So whereas the stealership wanted $300+ for a new cluster and $150 to install (for 10 minutes work too heh), now I'm gonna have a cluster for $80 and they are gonna charge me $40 to flash. So hopefully when the dust settles, I'll have a working cluster for $120. Thanks so much and will update as to whether it fixed my problem or not.

Edit: Oh, and it was reading buried way past 120 today when driving maybe 50. Farthest I've saw it off by far! And it started off reading correct when I left.

thenatural

Should have taken a picture and gloated. lol im jk