So i recently acquired a '96 F250 460 V8, but its the first of about 10 thats had obdII and all the added crap that goes with it, but anyways I start my list now, when i got this truck the speedo "jumps" but never exceeds current speed, we've replace everything we could think of including ecm, but recently noticed that 1 it still has the factory MAF and the CEL does not Illuminate when started.
no for the kickdown, when you step into the throttle to accelerate it will bog down a little , make foomp kind of noise, and slowly accelerate, we've replace fuel filter and CAT seems clear. please help.

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List of trucks owned; own
'76 Chevy, '78 F Series, '76 Chevy, '77 F Series, '88 F250, '89 F250;
'90 F250, '92 F250, '96 F250, '99 Silverado

 

The ECM (PCM) has nothing to do with the speedometer.
So you have a California truck.

 

I didn't replace ecm, a shop did but it didn't help anyways i think the Mass Airflow Sensor is bad but idk... and as for california i don't know what you mean

 

and the speedo isn't really the concern it's the inability to accelerate

 

Any F250 with a 460 and OBD-II would have to be a California truck other wise it would be OBD-I.

The speedometer may cause the inability to accelerate. Or to be more exact the PSOM output.

 

We have a '92 and tried swapping clusters and had no effect... and we had wires traced at a ford dealer, speed sensor replaced twice once with Aftermarket 2nd was OEM ford part, ecm replacement was aftermarket part ford dealer flashed (oem part was mia in warehouse)

Also looked into to it more the truck came up here (Omaha Surrounding Area) from Arizona.

 

I would check the TPS then.

 

Where is that on the 460? How much do they usually cost?

 

The TPS is at the end of the throttle shaft.


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Cost of a TPS is from $12.78-$39.79 at Rockauto.com:

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Should I just replace the MAF while I'm at it?

 

What is wrong with the MAF sensor?
Why do you ask?

 

I'm not sure there is anything wrong with it since i haven't had a chance to run diags myself...

 

Get a code scanner and check for codes yourself. Obviously throwing parts at the problem has not helped other than lightening your wallet. Continuing to do so is only going to make you more frustrated.

 

Only codes I get only when idling driving for 15 minutes or more and they disappear unexpectedly I have a video of the speedo and here is a bouncy video of speedo (road was pretty rough) https://youtu.be/-8pIf8O0lO4