Fell on its face when I pushed the trailer button

[mikeintn68]

I was hauling a slide in camper home last night. I was cruising around 70. I came to a very steep hill so I pushed the trailer button. The truck acted like it shifted into second and hit the rev limiter. I almost got ran over. I turned it off and changed lanes but was down to 35MPH before it allowed me to pick up speed.

On the next hill I left the trailer button alone (off) and all the truck would do is 55mph up this hill. I only had a 2100 lb empty slide in on the bed. The truck seems very under powered to me. Had I been pulling a trailer I would have been doing 35.

Other than the power issue it seems to run fine and gets between 17.5 and 15.5 mpg

Does anyone have any comments or suggestions?

The truck is a 2003 3500 crew cab Dually with 140K on it.

[DmaxMaverick]

Your first experience was "overdrive lockout". This makes 4th (direct) your highest gear. Max speed is around 75 MPH at governor, and a bit less on a grade as the fuel tapers off (it gradually slows fueling, rather than being an abrupt cut-off).

The second experience was Tow/Haul (you just went from one tow mode to another). If you don't get off the peddle, it won't upshift out of 3rd under a load, like ascending a grade with a camper in the bed (which happens to have a max MPH of about 55). Keeping it floored keeps it in 3rd.

I suggest reading your owner's manual. It describes how the T/H/OD button works.

Also, high profile loads, like a cab-over camper, are like parachutes. Huge wind drag, which plays a larger part of power demands than moderate weight loading.

And lastly, change your fuel filter. It can exaggerate any of the above if near time for service. It's always a good idea any time you're left scratching your head.

[mikeintn68]

Thanks for the info and I do understand the use of the tow/haul button I was just surprised when it almost caused a wreck. I would think the vehicle was smarter than to dang near shut its self down at 70mph.

Maybe I am expecting too much from this truck as I pull a hill with this camper and Dodges are passing me pulling giant fifth wheels.

[Mark Rinker]

Without more information, it hard to say what your root cause is, but agreed that checking/changing fuel and air filters first is a good idea if you are down on power with a 2003 LB7. Your first scenario sounds more like 'limp mode' - or a plugged fuel filter as DMax has suggested. If you live in salted road regions - I would change the filter regardless of how it looks; they are often salt encrusted and restricting flow at this time of year.

In general, the tow/haul mode is helpful when trailering, especially the grade braking features - for when you are on the other side of the hill.

Search and read in these forums, there is alot to learn about your truck. You shouldn't have to watch many Dodge's passing you in the future. :p

[Kennedy]

Definitely does not sound right. You were being power limited for some reason as ODLO should still allow you to run out to near 70mph if floored.

As mentioned above check/change fuel filter and transmission spin on. Also check crankcase oil level to be certain it is not over full which could indicate injector issues. Most likely a fuel filter if all is well mechanically.

Easy enough to verify with this:

http://www.kennedydiesel.com/images/Dmax-fuel-filter-rest1.gif

[DmaxMaverick]

Your "fell on its face" experience is absolutely predictable. You were running in OD, above the governed speed of the next lowest gear (4th-direct). When you locked out OD, it forced a downshift (which is what the PCM/TCM understood to be your intention). Once in 4th, the engine speed was above governed speed, so naturally, it fell on its face. If it slowed and you were still able to maintain about 70 MPH, your speed was reduced to about the maximum governed speed for that gear. No mystery here. None.

None of this sounds like limp mode. Your second hill experience could be any number of reasons. A plugged fuel/air filter may be a part of it, as the condition you set may have forced it outside its current operation envelope. If you had a limp mode experience, you would have had to stop, turn off and restart the engine to proceed with normal shifting, and you would not be able to maintain 55 MPH in any case (locked in 3rd gear, engine governed at about 2,000 RPM's). An overboost condition will temporarily reduce power and force a downshift from OD, but will resume normal operation within a few seconds of backing off the throttle a bit. This is near impossible in stock trim short of a glitch somewhere in the system. The boost-controlled wastegate and stock (or near stock) fuel rate just won't allow it.

A plugged filter can, and does, cause power reduction. However, it is not abrupt. You will just run out of power before it would normally, otherwise. You were able to get up to 70 before demanding the PCM/TCM change the operating conditions, so you had enough fuel, although you may have been right at the fuel flow limit when the episode began. 55 MPH is about the governed speed limit in 3rd gear. If ascending a grade and fuel flow is restricted, your throttle position to ground speed increase (in this case, none), prevents an upshift.

Change your filters and check for codes. Any power reduction commands will store a DTC in the computer for a while, but not permanently if the conditions don't repeat. You have several cold starts before they clear themselves. If no codes, the experience was driver-induced, with perhaps some help of air/fuel restriction.

[Kennedy]

Why did it drop to 35mph before allowing to pick up speed?

[mikeintn68]

Thanks for the info. I wasnt in Limp mode, Ive been there before when the Neutral Switch failed. Also, if I was in limp mode I should have had a light and there wasnt any. I will have the codes pulled to see what comes up.

The oil level is fine and I will change the fuel filter this weekend. I change it about every other oil change anyway.

Honestly, I have never felt like this truck has that much power when pulling a trailer. I usually pull a single car open car hauler with my street rod on it. I used to pull the same trailer and car with a 1/2 ton Z71 with a 5.3 and I swear it pulled just about as well. I thought with this truck and that load I wouldnt even slow down on a hill. I test drove a Ford with the 6.0 a while back and you could feel a huge difference in power. Is there anything else that will reduce the power? Turbo? Does a chip help?

[Mark Rinker]

There is something wrong with your truck. You should be accelerating up the hills described, with the loads described.

Do you see any black smoke from the exhaust during these situations?

[Kennedy]

Definitely does not sound right. You were being power limited for some reason as ODLO should still allow you to run out to near 70mph if floored.

As mentioned above check/change fuel filter and transmission spin on. Also check crankcase oil level to be certain it is not over full which could indicate injector issues. Most likely a fuel filter if all is well mechanically.



My bet again is that power was being limited due to a fuel delivery issue as noted above. Fuel issues like these are often RPM as well as load/demand related.

[mikeintn68]

No black smoke. The truck runs fine. Fuel milage is about what I would expect. The filter is about a year old (15K) but even when the filter was new the truck didnt have any more power than it does now. Although I am changing the filter today. I will let you know how it does after the change.

What else will cause low power?

[Mark Rinker]

If it is truely 'down on power', the root causes in order of likelihood:

Restricted fuel filter
Restricted air filter
Hugely oversize tires (>10% over stock diameter) with stock 3.73 gearing
All of the above
Low boost (turbo/wastegate/exhaust leak problems)
Low fuel pressure (weak injection pump, high injector return rates, etc.)
Some of the above
Low compression
Dragging brakes
Sun spots, Dutch Elm disease, Global Warming, etc...
None of the aboveMy observations only...

[mikeintn68]

OK,

Changed fuel filter,
Oil and oil filter
Air filter
Transmission filter


Pulled a single car trailer with a Datsun Z on it and on a slight grade the truck would not accelerate. I see guys hauling three cars on these trucks something is wrong.

How do I test the turbo?

[Mark Rinker]

When you couldn't accelerate, what was


Ground speed of truck
Gear
RPMsCan I assume you had the pedal to the floor?