sitting in park with engine either warm or cold i slowly push throttle and at around 1700rpm the 5.4 engine on my 97 f-250ld 4x4 will sputter and fall back to 1500rpm or so and holding my foot steady it'll come back to 1700 or so and fall back down and once i go over that it'll run just fine... its just at that one sweet spot that it sputters and stuff.... really weird and sets no codes and i only notice it when its parked at an idle but it does it with engine cold or hot...any tips, ideas or suggestions would be helpful...thanks

 

Throttle position sensor.
Probably has a dead spot.

You'll need to check it with an ohm meter to be sure, it should smoothly change resistance as you move it.

It won't set a code because it's not open or shorted.

if it gets erratic enough it may set a code.

On my 91 I had a "sweet spot" just off idle where the idle would roll like an old detroit diesel until it would finally stall.

 

hey thanks, i have a over the counter book that covers most tests like that and i work at John Deere Imp as a technician so that wont be any trouble to test and replace if required

 

hey i changed the tps cuz it was cheap and it has same issue, 1450 is the spot and has always been the spot, i mistyped it in initial post, hits 1450 and sputters and u can take it up or down and its fine, if u dont take it up it'll fall down a few houndred rpm and come back, its not super easy to hit the spot but u can tell when u go by it slowly, when u rev it u cant tell, any other thoughts?
thanks
jon

 

could be anything from a dirty MAF, to some bad plugs, to some bad coil on plugs.

start cheap and easy and work your way up to the bigger stuff. get some MAF cleaner, be really careful, pull your plugs and inspect them, replace if necessary. test your coil on plugs with an ohm meter.

 

I would bet that if you get hold of a good "scanner" and look at the operating paramenters before and during the issue, it would lead to a suspect fault.
Good luck.

 

sounds like a TPS. And yes, use a good scanner not just a code reader. Something that will give live readouts.

 

apparently you fail at reading, because he already replaced it........

 

I had the same problem. It was a bad boot on a COP. It wasn't malfunctioning 100% of the time, so there were no codes and with a multimeter it read fine, but I swapped it out with a known good cop, and all is well now. Luckily it was COP #2 so it was right at the front, and easy to get to.

 

This kind of issue is really difficult in that not having any scan tools, so this next few ideas is real shadetree.
first does this problem happen when driving? or is only when "revin it up"
Im sure you have disconnected the EGR valve and tried it, did it make any change?
How about the base timing is it at 10 degrees BTDC when you have the spout connector disconnected.
what about the fuel system, have you got a good fuel filter.
Then at last comes the PCM you may have to get a known good pcm to ensure it's ok. Have you been jumping others with the engine running? of course I hope you have never disconnected the battery cable while the engine was running...let me know if you find anything

 

well when driving i dont notice it but it would b really hard 2 actually notice, i suspect in town it may shift when it happens and i cant tell but i really dont know, and i take the rpm's up really slow to notice it and have to hold it right at the spot to make it do it, i dont notice it when i take the rpm's up fast. i havent disconnected the egr to try it... what part should i disconnect to try that? the whole timing bit i havent looked at and am not going to dig that deep into it unless it gets worse and affects the drivability of the truck.... the fuel filter and tank are new within less than a year ago... and im unsure what u mean with the pcm... are u meaning the ECU? engine control unit?? i have done some jump starting with engine running, what farmer doesnt and i have never taken battery cable off while engine running.

 

On the EGR valve there is a little vacume line, just unplug it and then retry running the engine for the surge. The timing is something that should be checked from time to time because as the engine wears it will change the timing (as the timing chain wears the timing changes, usally around 90K miles on up is when you need to start looking at it.) And yes the powertrain control module is aka ECU. good luck