rpm gauge going crazy

[pimp800]

alright guys im a newbie here. so please help me out here.. here's the deal, today i noticed my rpm gauge was at 3500 at idle,(the truck wasnt reving). so i pulled over and cut the truck off and the needle dropped to about 2500. i crank it back up and go down the road , and my rpm gauge pegs my turbo gauge hit each other. so i get home, pull my dash and adjust the needle by hand back to its proper location and fire it back up and no problems.. went down the road a few hours later and i look at the needle and its doing the same thing.. any help would be greatly appreciated.. by the way its a 6.0 2005 f250..

 

[Zookie400]

sounds like you could have a failed guage, or a wiring issue. the truck was still running fine wich makes me believe the engine harness and sensors are all ok, i bet its an in-cab problem. you need to get your hands on some wiring diags for the truck and see where the signal wire(s) are and get some pinout info.

 

[fordoor]

There was a Broadcast message #3695 from Ford that was specific to 05' speedometer needle bounce. Whether it applies to your Tach. issue, I don't know. It says to "inspect the wiring harness running behind the coolant bottle to the wiper motor for chafing on a brake clip and shorting to ground. If harness damage is found, repair and insulate the damage, and secure away from the clip". Hope this works! Also, WELCOME TO SDD!

 

[caissiel]

On new years eve my RPM gauge went way up to 3500 at idle. I checked my scangauge rpm and it showed normak RPM. When I shutdown the engine, the gauge stays above 2500, This was second time my dash gauges failed in 2 weeks. My boost gauge also stuck to zero while my Scangauge showed Normal pressures. All I can say its dash related, but why does it stick to 2500 while the truck is off. I though it was the cold that did it. My ScanGaugeII let me operate without any worries, one more great use for this gauge. Best Tool I ever bought. I Do have a problem with the Speedometer, it comes down and the engine light comes on and no codes are indicated and can be cleared. I changed the speed sensor on the rearend and it still did it after. Also the turbo gauge problem sets the Codes and so far while the Boost gauge is now in proportion with the scangauge, the code cannot be reset. It Keeps comming back.

 

[caissiel]

Well I went on a 5 hr trip today with my truck, The RPM Gauge was at 2800 when engine not running and up to 4800 Rpm on the Highway. My Boost gauge showed 0 all the way down. And when I arrived the truck kept bucking and could not accelerate. Black and white Smoke filled the street, I think I was running in Limp Mode. So I reprogramed my truck back to stock. All the problems are now fixed, and the Engine light stays off. I think the RPM Gauge stays up at the RPM Indication when engine is shutdown, just like the fuel gauge. I Upgraded my Programer last month and reloaded it to my truck, It realy never operated as usual since, I blamed it on the -30 to -40 Weather here. I think my download did not work well, so the programer skipped some important loads when I reprogramed. I will redownload the updates and try again.

So My Problems were completely programing created.

I never tought it was programing because my ScangaugeII never stop indicating the proper Boost and RPM.