Community Forums

ardbark · 03-25-2012, 11:03 PM

So here's one. I'm driving over Sardine pass the other day (outisde of Logan Utah) and my throttle sticks - almost wide open. With a LOT of braking power I got the rig off the side of the road and shut it down. After cleaning the drivers seat :-) I fired it back up and it immediately went to 2250 RPM, couldn't get it to throttle down. I started and stoped the engine seveal times, same result. After manually playing around with the linkage going into the fuel pump (fuel control?) it settled back down enough to get the rig home.

Lubed all the pivot points on the linkage plus as much of the cable as was exposed, changed the return springs (stiffer) and its better, but it still won't fully return. Idle speed is now at close to 900. If I manually move the linkage it will fully retard and come down to 650 or so, but soon as I touch the throttle it won't return to the full closed position.

Scenario
1996 36' Endeavor, 5.9 12v Cummins

Symptoms

- I did run the cruise control for the first time, a KC 2500 Cruise King, which is a vacuum unit.
- When it was idleing at 2250 I could accelarate but it would only drop back down to 2250, so the throttle cable was moving back and forth through the jacket.
- When it stuck open, after shutting the key off the RPM gauge stayed at 2250. Once I put the key in the start position the tach resets to zero.
- While manually moving the linkage it "feels" like it wants to return to the full closed position but the last 3 or 4 degrees (1/4" of travel?)the linkage "drags"? Sort of feels linke there is a rough spot just before closing? Hard to explain.

Although I changed the springs I don't think they are the culprit. I'm thinking its either something to do with the cruise vauum system not releasing fully or something inside the pump (rack?) all gummed up, but those are just guesses.

If anybody has seen this before or has any ideas I'd be mightly pleased to hear them.

cheers...

Mike Canter · 03-26-2012, 06:16 AM

I had the throttle lever on the throttle body on the motor crack and cause problems like that. It is the lever that the morse cable is attached to. The replacement lever I bought was made differently to prevent that from happening again.

sc3283 · 03-27-2012, 10:10 AM

Can you remove the throttle cable from the injector pump, then move the arm on the pump and work the throttle pedal to see which is the problem?

ardbark · 03-27-2012, 01:34 PM

Quote:

Originally Posted by sc3283

Can you remove the throttle cable from the injector pump, then move the arm on the pump and work the throttle pedal to see which is the problem?

That's a good idea, but since I was scheduled for a full service and have the new Bilsteins installed today anyhow, I turned it over to the pros at the Freightliner shop.

Besides being scary and dangerous the coach was becoming undrivable as the Allison wouldn't drop into gear idling at 950 or 1000. Just to get it in Drive this morning I had to go back and manually retard the linkage so the idle came down enough to make Mr. Allison happy.

Should hear back from the shop later today, I'll post the results.

ardbark · 03-27-2012, 11:03 PM

Got the coach back from the shop this evening. New Bilstiens are heaven on earth, HUGE difference. Along with the shocks and a complete lube/fluid/filter service they also fixed the sticky linkage.

The mechanic was already gone by the time I got there but from what the shop forman told me it had something to do with "too sharp an angle" somewhere. I'll try and touch base with the mech tomorrow and get more info so if it ever happens again I'll have an idea what to do.

I think it is still idling too high, around 775-800 RPM, but at least the transmission will now go into gear. Anybody know what a 5.9B 12v should idle at?

Anywho, the list is getting smaller. We're down to new steer tires (I'm leaning towards BF Goodrich's right now), new windshields (somebody B-B gunned mine over the winter) and a pyrometer, boost and maybe a trans temp guage.

Then we camp. Or RV, or whatever we are calling it these days

ardbark · 03-28-2012, 09:42 PM

Quote:

Originally Posted by ardbark

Got the coach back from the shop this evening. New Bilstiens are heaven on earth, HUGE difference. Along with the shocks and a complete lube/fluid/filter service they also fixed the sticky linkage.

The mechanic was already gone by the time I got there but from what the shop forman told me it had something to do with "too sharp an angle" somewhere. I'll try and touch base with the mech tomorrow and get more info so if it ever happens again I'll have an idea what to do.

I think it is still idling too high, around 775-800 RPM, but at least the transmission will now go into gear. Anybody know what a 5.9B 12v should idle at?

Anywho, the list is getting smaller. We're down to new steer tires (I'm leaning towards BF Goodrich's right now), new windshields (somebody B-B gunned mine over the winter) and a pyrometer, boost and maybe a trans temp guage.

Then we camp. Or RV, or whatever we are calling it these days

On the idle question, checked the ID plate on the 5.9 Cummins and it states 800 RPM idle speed, which is what I am at now. Man, that seems high. When stopped at a red light or whatever I have to brake pretty hard to keep the coach from creeping.

Does 800 RPM idle seem normal for your DP? It's like the coach wants to go all the time, and it feels like I'm always feathering the brakes to keep it in check, at least when it town on 25 mph roads, or going through gutters getting into gas stations or what have you.

cheers...

sc3283 · 03-29-2012, 10:12 AM

Mine is an 8.3 so can't compare to yours but mine idles @ 700ish

Arch Hoagland · 03-29-2012, 12:04 PM

When I hear of stuck open throttle I always wonder if the driver put the vehicle in neutral as a way of controlling the vehicle while they are stopping.

You mentioned "with a lot of braking power" you got off the road.

I'm curious if you put it in neutral when you were trying to stop.

ardbark · 03-29-2012, 01:24 PM

Quote:

Originally Posted by Arch Hoagland

When I hear of stuck open throttle I always wonder if the driver put the vehicle in neutral as a way of controlling the vehicle while they are stopping.

You mentioned "with a lot of braking power" you got off the road.

I'm curious if you put it in neutral when you were trying to stop.

Nope. I was able to get her slowed down enough with the service break to get off the main canyon road, onto a secondary road, stopped and into neutral. Its only then, when the tach went straight to 2250 that I fully realized what had happened.

If it had been a run-away situation neutral would be an option, assuming the Allison would even let me put it in neutral running at speed, which I'm not at all sure of.

Arch Hoagland · 03-29-2012, 09:45 PM

I'd be curious too if the transmission would let you put it in neutral while trying to accelerate.
I have the 1000 model.

Does anybody have any info on putting a Allison in neutral while at higher RPM?

sc3283 · 03-29-2012, 09:56 PM

My Allison 1000 will go into N if the shift lever is put into N at any speed or any engine RPM

Arch Hoagland · 03-29-2012, 10:53 PM

@sc3283 Thanks for the info.

Think I'll give mine a try this week as we are headed out on a trip.

ardbark · 04-18-2012, 09:21 PM

Quote:

Originally Posted by sc3283

Can you remove the throttle cable from the injector pump, then move the arm on the pump and work the throttle pedal to see which is the problem?

As an update on this problem it turnes out not to be the throttle cable but the cruise control cable. The CC cable is short, not more than 18 inches and makes a pretty tight turn out of the CC box to the injector linkage. The Freightliner shop claimed to have fixed it by re-routing the cable but that's crap. It's too short to re-route anywhere.

I've proved its the CC cable 3 times now, everything is fine until I set the cruise, then the throttle sticks at whatever speed I set the cruise at. I don't really think it is so much the tight turn, the cable has been on there since 1996, I suspect it just needs lube, which is the next step. Why a dealership couldn't figure this out is beyond me.