Runaway idle, need advice please
 

So this morning, upon start up, after a few minutes my idle started to climb rapidly in the manner of a runaway diesel. I shut the car down, waited a few moments, and drove the car off (82 300sd) and then parked with the car at a normal idle. Again, the idle began to climb rapidly (only in park) what gives? It does ,for the first time, a tank full of bio diesel (versus diesel) and has been running great on this . . .could this have anything to do with the runaway idle? What might cause this situation, help! Thanks!

how high does it go to?

If it was a run away you would not be able to shut it off without using a Co2 fire extinguisher into the intake or a chunk of wood to block the intake....

it just starts to climb faster and faster, I am able to shut it down with the key -

Does the accelerator move when this happens? I'm wondering if the cruise control actuator connected to the linkage is trying to activate. Had a POS Ford that would do that.

does it keep climbing, or does it peake out?

I just checked and cannot seem to duplicate climbing idle situation. I am going to keep an eye on this and will also check air cleaner, turbo play, and oil consumption, etc. to ensure that I do not have all the elements to create a runaway diesel scenario . . . .thanks!

if it did "peak out" what would that indicate?

If you were able to shut it off with the key, it is not a runaway diesel. So you have no need to check for these elements in your troubleshooting of the problem (although it wouldn't hurt just so you can get to know your car better). Maybe your accelerator linkage needs adjustment. While in drive, the TC+trans presents enough load to the engine to keep the RPM low. When shifted into neutral or park, the load goes away, and the engine will rev higher and higher. It takes a surprisingly small amount of pedal to do this, so if your linkage is adjusted wrong, it could happen.

If it "peaked out" at somewhere around 4800RPM, then the governor in the IP is taking over.

Thanks, just seems odd that linkage adjustment would change overnight like that . . . . have to keep an eye on this !

I just had a problem somewhat like this and it turned out to be the linkage. It only did it on cold mornings. I popped all the linkages off that I could get to and lubed them with white grease. No more problems.
This was on my 91 300D 2.5 Turbo.

thanks, I will try this and see if I get a good result -

Now that I think back I did have a similar problem on mine. On cold mornings the linkage would become stiff and not return to idle immediately when the pedal was let off. It kind of scared me the first cold morning of that winter, I let off the pedal and she kept going for a little bit :P. Once the engine heat rose up to the linkage, it would loosen up and be fine. All it needed was a little more grease.

The most likely cause is a severely worn out Engine Mount. This will allow the engine to shift positions pulling the accelerator cable, and or linkages with it.

My 82 300SD started to do this same thing two days ago....did you find the problem? Is there a simple fix? Is this common?

How high is your idle?