94 7.3idi accelerating on its own

[wlf89]

i have a 94 idi that i use to haul cows and hay with mostly. i have had the truck about 3 years but doesnt get used to much. few weeks ago when i was hauling load of cows. while pulling a hill about 55mph it suddenly accelerated on its own and i immediatly let off the throttle and it stopped. since then it has done it couple more times. the last time it done it and no traffic was around so i held the pedal constant and it kept picking up speed. went from 60-70mph before i let off and it came back down but not smoothly, kinda came back down in rpms in steps.

im not sure what is causing it, the 4 or so times it has done it seems to always be going 55-60 and higher rpms when pulling hills or a load.

also not sure if related but at higher rpms (tach doesnt work so not sure actual range) just as getting ready to shift gears there is a squeak/squeal im thinking exhaust or turbo joint leak.

other than that it runs good and starts good. no smoke or nothing out of the ordinary.

anyone ever had this problem or ideas whats going on? thanks in advance.

 

[themechanicalford]

Starved for fuel from a low tank. Also going up a hill could have pushed the fuel to the back of the tank. Mine bucks like a wild horse when it gets low and starved like that.

 

[Cubey]

was your tank around 1/4 full when going up the hills and it happened? could be air being sucked in from the fuel pickup "shower head" having fallen off

Do you have a c6 transmission or e4od? tach sensor working is needed for e4od but not c6

 

[Vern]

A few things could cause the starvation "surge". If full tank corrects it (if you can afford it) that's an important clue. "stepping down" tells me recovery is somehow incremental and that pump might be sticky inside, perhaps.

 

[lotzagoodstuff]

Silly question: do you have cruise control? I have seen some older cruise controls go back to "resume" all by themselves. I call this the "keeping you awake" feature

 

[wlf89]

no cruise control. its the 5 speed manual,full tank of diesel. and the fuel pump is the facet duralift, i cant remember the model but its the one yall recommended on here. if it was fuel starvation wouldnt that make it run bad? when this happens its like a gas engine opening up the 4 barrel, it opens up and takes off like its got more power.

 

[lotzagoodstuff]

the fuel pump is the facet duralift, i cant remember the model but its the one yall recommended on here.

The facet pumps are a little suspect for not keeping up with a healthy IDI under load. I'll bet you two drinks that it's related to the pump. Where do you have it mounted, related to being "uphill" from the fuel tanks? I would also take a look at anyplace you could have some blockage, most suspect to me would be the shower heads in the fuel tank(s). Have you had your sending units out and inspected one or both tanks?

Lastly, fill out your signature so we know what year/make/model/miles/etc as it can help to know what you have.

 

[Cubey]

it opens up and takes off like its got more power.

Yep, that's what mild air intrusion does. Heavy air intrusion would make it run badly.

My NA F250 kept doing it in Wyoming on i80 EB, maybe somehow related to the heavy winds since it was reasonably flat.

I don't think my ATS 085 motorhome has ever done it, at least not to my recollection.

 

[IDIBRONCO]

There's also been people who say that the bowl on the bottom of their Duralifts have leaked slightly and allowed air into the system. This sure sounds like air intrusion to me. I don't remember hearing of it being extended for so long, but it's still what I first thought of.

 

[Big Bart]

Two thoughts -

Oil the throttle linkages and the parts on the IP the throttle linkage moves. Perhaps the throttle is getting stuck or the IP is sticking. So you let off a little bit, but it sticks, till you let all the way off And the springs pop it back.

Second inspect, clean, and replace if needed your cdr valve. Perhaps at high rpm you are dripping oil or via blow by you are misting oil into the intake and having a small case of diesel engine run away. It will burn like diesel. It is recommended to clean the cdr every 15k miles. Folks have reported issues and blown head gaskets if too much oil makes it into the intake via the cdr valve.

 

[Brian Wagner]

I can tell you what that little squeal is, your fan belts are getting old and a little loose

 

[jwsfarrier]

I ran a Facet pump in my 89 for a minute. I had similar expieriences. Get rid of the Facet pump!

 

[wlf89]

I can tell you what that little squeal is, your fan belts are getting old and a little loose

i hope not its only 1.5yr old