weird rev thing - Ford Powerstroke Diesel Forum
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Old 01-11-2014, 03:20 PM
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Unhappy weird rev thing

Im new on here as well as new to Fords and Diesels so bear with me on my limited understanding of things. I recently purchased a 2002 F250 7.3L Powerstroke from a small dealership so Im not sure how it was maintained but seems to be in great shape mechanically as well as cosmetically. It has 160,000 miles and after buying it had the oil and tranny fluid done. After hooking up to a average size landscaping trailer with my ATV on it (only time I have pulled anything with it) I was doing 65mph on the freeway. I decided to bump it up to 70mph pretty quickly and all was fine for a couple miles. Then all of a sudden my engine started to rev up by itself and the rpm and speedomoter would also go up and down but the truck was'nt actually speeding up or going any faster. I thought maybe tranny but that wouldnt make my speedomoter go up? Is it maybe a computer thing? Or just freak occurance maybe? Hasnt done it since but kinda scared to pull my 28' fifthwheel with it this summer. Any opinions????
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Old 01-11-2014, 03:22 PM
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Sounds like an electrical issue. Was it raining?
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Old 01-11-2014, 07:44 PM
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No, it was cold out but it was pretty dry.
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Old 01-12-2014, 03:09 AM
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If the engine revved up then you had to speed up. How much are we talking?

If it was just the gauges but the engine speed stayed the same I'd agree on electrical. Otherwise to me it sounds like a lock up issue
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Old 01-12-2014, 04:57 AM
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Sounds like the speed sensor located on the diferential or the wiring to it.
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Old 01-12-2014, 07:24 AM
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The engine definitely revved up and the speedometer also went up with the rpm's but the trucks actuall speed did not change. Closest thing I can compare it to is spinning on ice but that was definitely not the case.
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Old 01-12-2014, 07:33 AM
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Does your truck behave weird taking off from stops, or shifting? By any chance did you notice of the O/D light on your shifter was flashing? To me this sounds like the the trans slipping and the engine revving to compensate. I believe there is a Speed sensor in the transmission too, and the PCM uses that, along with the ABS sensor in the Rear diff for shift calibrations.

Did you feel like the truck was actually speeding up or slowing down?
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Old 01-12-2014, 07:41 AM
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Truck acts completely normal at all times and hasn't done it since but I haven't pulled anything since then either. No dash lights came on either. Truck never sped up with the revving it did seem to feel like it lost power at the time it was doing it though.
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Old 01-12-2014, 11:32 AM
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Again how much did the Rpms and speedo go up?
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Old 01-12-2014, 04:18 PM
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The rpm's went from 2,000 to around 2,500-3,000 and the speedo from 70 to about 80.
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