2003 Dodge Dakota that doen't seem to like towing


#1

I have a 03 Dodge Dakota with the 4.7L engine, and I tow a camper which is around 5000lbs. I don’t have a problem while towing, however by the time I get to my destination the engine idle becomes very rough sometimes stalls (need to leave the A/C on in order to keep it from stalling at every stop sign). This goes on throughtout the vacation and until we return, where when I arrive home the engine (idle) is running as always, just fine. Needless to say I was never able to get it in to a repair shop because the problem seems to go away when I return. This has happened about every time I tow the camper. Somebody told me that the throttle position sensor is not working properly, I never investigated. Any ideas??


#2

A throttle position sensor fault would be present all the time.

If you need to have the A/C on (which activates extra cooling fans) the engine must be running too hot, hence the rough idle.

When I say ‘hot’ I don’t mean boiling over.

Have you got a heavy duty rad and oil cooler and tranny cooler in the truck?

After looking at the specs for your vehicle (in the ‘research’ link here), I see the standard rear end gear ratio is 3.21 (made for the best mileage with an empty vehicle like most, if not all vehicles)

Have you got a higher (numbered) gear in the rear end? If not, this will also contribute to a hotter running engine due to extra work when pulling a trailer. (you have three choices) 3.21/3.55 (I would recommend this one) or the 3.92.

A low ‘numbered’ rear gear ratio means the highest MPG rating, but causes problems when towing heavy loads.
A high ‘numbered’ one means less work for the tow vehicle, BUT a bit LESS mpg rating.

Changing gears to get the wanted ratio is usually not recommended, unless a highly skilled tech does the replacement there will be a permanent howl as a result. It must be very fine tuned to be done correctly and that is quite expensive.

4x4s are even more $$ as the front diff must match the rear one.

If your truck doesn’t perform like this when you do NOT tow your camper, then the wind drag from the camper (which is quite substantial) is putting an extra strain on the truck causing the engine to run hotter than it should be.

Does this rough running symptom occur if you tow the camper around close to where you live?
I’m thinking about summertime ambient temperature differences and also varying terrain. (height above sea level included)

My 21’ travel trailer hauler is a used '02 Chev Tahoe 5.3L V8 and 3.73 ratio. I wanted a 2wd truck but couldn’t find a used one with a 3.73 ratio.


#3

That truck is way too small to tow that kind of weight and load. You are probably overheating it and causing damage. Get a bigger truck.

Skip


#4

Skipper may be right. I was checking the tow rating for these trucks (albeit the 2008 models), and the Dakotas with this same engine and 2WD are rated to tow a bit over 7,000 lbs. However, with 4WD they’re rated at only 4,500 lbs. It’s a fairly safe bet that tow rating hasn’t decreased in five years…


#5

SORRY!

NO MOPAR PRODUCT LIKES TOWING,(seems to be a weak link(the transmission)

but the ammcos LOVE when you tow ,extra CASH.


#6

I agree with the overheating scenario. That seems like a lot of weight to me but I’m not that familiar with the specs on these trucks either.
Hopefully this truck has a towing package because an overheating engine is going to overheat the transmission fluid which in turn is going to mean a short transmission life.

You could consider getting the truck scanned (AutoZone, Checkers, etc. will do it free) and find out if any codes related to the ECT sensor or TPS switch being out of range are present. The latter is not likely IMHO; just mentioning it because of your TPS comment.


#7

Thanks for all the input, however I am not yet convinced. I agree that I am towing a bit out of the range of my vehicle, with the 3.55 axle ratio I have the spec shows max towing is 4450lbs (thats Gross Combined weight spec - Curb weight - 150lbs (150lb for driver?? maybe I need to loose some weight?), if I had a 3.92 axle ratio I could tow 5750, thats 1300lbs more. It would seem that if I upgraded axle ratio to the 3.92, that would cause the engine rpm’s to increase at cruising, this then would increase heat, I think this powertrain should be able to take some load since its the same used in full sized trucks. Also I want to clarify that the engine runs like crap when not towing, in otherwords, I drop off the camper at the camp site, and do my sightseeing, ie driving around without the camper in tow, and still runs like crap. I tow the thing back home, park it at the storage facility drive home, and everything is ok, runs smooth as could be, so the issue arises sometime during the trip in tow there and corrects itself sometime during the trip in tow back. This is telling be that there is some module that is learning or adjusting something, and it takes time to correct itself, whether there is a faulty component, or something else is what I am trying to find out.


#8

Well, the clarification actually adds to the mystery.

Do you stop at the same place for gas each time you tow? Exactly when does the problem occur, as soon as you take off with the camper hitched? When exactly does the problem resolve itself, as soon as you unhitch at the storage facility?


#9

Then you need to get the truck scanned as step 1 instead of relying on things like someone told you the TPS is not working properly and which you never investigated.


#10

I am wondering if you are at a higher elevation when you are on vacation? The problem might relate to the lower air density at altitude.

The problem might be in the Idle Air Control system. You might just need to have the throttle body cleaned with emphasis on the idle air passage and the IAC pintle. This may not be the case if the AC does not use a separate air bypass for idle upspeed.

Otherwise, look at the MAP sensor and its vacuum line to the manifold. This is unlikely to be the problem as a defective MAP sensor or its vacuum source will usually cause a lot more problems than just poor idle. However, the PCM gets its ambient air pressure reference from the MAP sensor just before the engine is started.

Hope I am leading you in the right direction.

I suspect that somehow the PCM does not know that the truck is at a higher elevation and so does not adapt to the lower ambient air pressure.


#11

Well, there’s not much else I can add, except regarding the 3.92 rear end.

Yes, the engine would rev higher, the MPG would back off about 2 mpg but higher rpms with the proper heavy duty rad, tranny cooler, etc. would not cause any over-heating.

One thing comes to mind: does your truck have a ‘tow haul’ mode for towing?

Auto or standard? (GM uses a ‘tow haul’ switch in the end of the shifter handle you can set to prevent the tranny from constantly hunting.

If not, use the next gear down from the overdrive.