Engine run away HELP PLEASE

[TJMIV]

Have a very good friend with an 04.5 3500 DRW 4X4 automatic & his situation is as follows. Over the last several months when he gets in his truck to go somewhere for the first time that day, @ some point it just takes off full throttle on it`s own. This beast is like a run away freight train until he stands on the brakes. At that point the RPM`S drops & sounds like it`s not even running & throttle pedal does nothing. All of a sudden the tachometer pops back up @ about 800-1000 RPM`S & it runs normal after that. This always occurs before the engine comes up to operating temperature & never has done this after reaching operating temperature. He dropped it off @ a dealership & they told him it was the lift pump & they installed the in tank version. Still does the same thing as before, he had it back over to the dealership & they can`t tell him what`s going on even though he has spent about $2000.00 with them to fix it. Several weeks ago when it was in the low 20`s one morning, he started the truck to let it warm up before he left home & after a few minutes he heard the RPM`S sky rocket, had to run out of his house & cut the switch off as it was sitting there running @ 3500 RPM`S. He bought this truck new & doesn`t want to get rid of it, but this thing has him kinda shook up with the way it`s acting. He`s had enough of the surprise 7000lb rocketship rides. Thank you in advance for any & all help that anyone out there can offer.

 

[seafish]

Diesel engine runaways are caused by oil or oil vapor leaks into the air intake. That beoing said, your friend should STOP driving his truck immediately until he finds the cause of the runs away as it is inherently unsafe to drive a truck that might runaway at any moment. Then I suggest that he remove the turbo to IC pipe and inspect the pipe for oil residue. While somewhat rare, likely the turbo journal bearing and or seals are leaking and allowing oil directly into the intake. If that is the case, a rebuild kit for the turbo, or a rebuilt turbo, will solve the problem of the run away.

 

[BigPapa]

If this were a true run away, shutting the key off wouldn't stop it and nor would standing on the brakes.

There is some electrical or electronic issue behind this.

I agree he doesn't need to drive it until the issue is found.

 

[Wayne M.]

Had a runaway ford 6.4. The deal is this-
Ran fine. Blip the throttle and on the third blip, it would take off. Controlled by the key everytime. I found the crankcase was filled to the valve covers and was pumping into the intake vent whistle at the airbox. This filled the intercooler and polluted the whole intake. The design of the 6.4 IC is that the in side is low. I popped the hose and got a pint of diluted engine oil out. I drained over 40 quarts from the oil pan. Still waiting on a decision to rip this one apart, but obviously an injector line is spraying inside the engine.

This is just food for thought.

 

[mwilson]

Wouldn't that be an electronic throttle pedal??? I know my '06 is, never sure on the 03-04 trucks.

If so, the throttle position sensor could be wasted.......

 

[CBari]

Had a similar but nowhere as severe a problem on the 03 at one time, mine was tied to the apps replaced it and eliminated the problem. It was hard to pinpoint when it would happen but throttle would be unresponsive when it did. I never really raced like this one is doing it would just stay at what ever throttle setting was seen last.

 

[Wayne M.]

The APPS causing a runaway is a long shot. There are multiple scales that validate each other and if one don't reference it'll go limp. Or the MIL will come on.

 

[mweiman]

unplugging the apps and starting it cold may be a cheap way to start troubleshooting. If it doesn't do it I would say that rules out the oil/vapor in the intake theory.
Matt

 

[fox]

Define 'runaway' more.
Is it reving to the moon, or is it redlining like it is governed?
Big differences.
If it goes way higher than the rev limit it is fueled by an outside source, like fuel/oil in the intake, or propane leak by a nearby source.
If it revs to 4,000 by itself it is electronic runaway. Bad sensor somewhere.