Idle "runaway" and other wierd symptom

[Andrew M. Frankli]

Once in a while my '93 IDI non-turbo 7.3 will "runaway"... by that I mean I will accellerate gently and the truck will take off like I floored it for a second. Nothing dangerous, but kind of unsettling. Happens especially when cool - within 2 miles of home. Another thing just started happening too - When idling the truck will idle real "lurchy" - like the engine is going to die than "fires" then almost dies... Did this for 2 minutes. When I revved it the engine sounded smooth, but then did this lurchy idle thing again. Then went away. Anyone ever experienced something like this?? Any ideas?? THanks. Andy

 

[pafixitman]

Air, pump going out, clogged CDR are my top 3 guesses.

Try a healthy dose of fuel conditioner and see if it goes away. Do you have any fuel leaking from the pump?

 

[tuckerd1]

Mine acted similiar once and turned out to be dirty fuel filter. Replaced it and never had the trouble again.

 

[82fordtruck]

mine always does that until the fast idle goes off, then behaves wonderfully.

 

[Russ]

Sounds like air in the fuel lines to me . Are there ANY wet spots near the injectors or fuel lines? If the truck gets air in the fuel system it will rev temporally for a few seconds.

 

[olivera149]

are you seeing any smoke, white or black when its surging or running rough?

 

[Marks Garage]

Mine did it one day and it was the fuel filter.

 

[82fordtruck]

Mine doesn't. I assume his doesn't either. It's like it really wants to be revving over 3k rpm's.

 

[Agnem]

Definitely fuel starvation due to air, or fuel supply issues. Air is the most likely suspect, since you indicate it does this shortly after you leave the house, and probably doesn't do it again for the rest of the trip until you shut it off. Do yourself a favor and R&R your return lines. See my fuel injection servicing article in the Tech Articles at the top of this forum.

 

[82fordtruck]

Maybe ours are different problems, but mine are brand new. I still maintain that this is an IP problem.

 

[82fordtruck]

As far as the "lurchy" thing -

Does it rev itself? Is that what you mean? Or maybe just a rough idle?

 

[Andrew M. Frankli]

WOW! Thanks for all the help...

There are no fuel leaks around the pump, injectors, nor lines. Filter is only a few months old. It kind of does "rev itself", or more accurately, almost dies and then surges to idle speed and then back down to almost dying again. The 6 or 8 times it has done this I have immediately switched tanks just to "do something" and the engine has never died. Next time I will just let it roll and see what happens. Never has this precursed an empty fuel tank; when I run out of fuel it simply dies instantly and that's it. Then switch to the other tank, crank 3 or 4 sets of 30 seconds and I'm on my way. Thanks for all the help, friends. Sincerely, Andy. PS No more smoke than usual when it's doing this. Doesn't seem to be "rough idle", more like water torture!

 

[82fordtruck]

It runs out of fuel??

We do have different problems. I'll stop hijacking the post then.

 

[82fordtruck]

Then I also think you have a return line leak somewhere. That is what is letting the fuel drain back into the tank.