I have an 2002 Dakota with the 4.7 V8 and 210,000 miles. A few months ago the truck began running rough while accelerating - but only during the daytime. In the evening it's as smooth as can be. It's more pronounced if I apply the gas strongly. If I apply gas gradually, it is not apparent. Let me say that it's summer here in SC. That means hot and humid.

I thought about moisture in the fuel tank or dirty injectors. That doesn't fit with daytime / nighttime difference in performance. I still ran two tanks of gas with gas conditioner, and two tanks with injector cleaner. That didn't work.

I'm figuring to do plugs and plug wires next, but wanted to see if the symptoms ring any bells before I do any costly experiments.

Thanks for any suggestions,

Tom

 

Well, if it's really hot out, the incoming air will be hot and can throw your tuning off. Could be just the tune itself, but a it could be due in part to a worn O2 sensor, or IAT sensor or something like that.

Can you explain what you mean by running rough while accelerating? Does it misfire?

 

well you'll be doing only plugs on your 4.7.. do some basic preventive maintenance, change the spark plugs, i would do the o2 sensors as well since they have a service life of approx. 60K miles. they wont always throw a CEL, never the less i dont know of anyone with these trucks that threw a CEL with a bad o2 unless the wire is cut. it would be good to replace your map sensor since they tend to have a carbon build up on them over time and start to read incorrectly. clean the throttle body is also a very good choice. in the long run, it maybe a faulty coil pack ( you have 8, one for each cylinder) but i highly doubt thats the case. good luck

 

By rough I mean there is a definite "lurching" as the speed increases. I'm trying to describe what I'm actually feeling. It can't be heard, but it can certainly be felt in the pedal, wheel and seat. My brother commented on it while riding as a passenger. It doesn't feel or sound like the classic "misfire" I'm used to hearing on older vehicles. Maybe the rifle report and blast of fire from the tailpipe is a thing of the past?

Flooring the pedal does not get past the symptom. But as I said in the first post, gently accelerating does not exhibit the problem. The symptom is evident no matter what speed I begin to accelerate from.

The temp's here lately have been 85 to 95 with humidity from 65 to 75 %. (Let me say that I appreciate how parts of the southwest are much hotter, and how the DEEP south is more humid.) The lows are from 70 to 75.

Tom

 

A coil pack problem should throw a misfire code if it's notable, I'd think.

 

well what i should of asked for first was, no check engine light? start with what i mentioned, spark plugs then clean the throttle body. at 210,000 miles, gonna need some TLC, unless maintained religiously (which nearly everyone is guilty of, even the guy who wipes his cars clean with diapers).

 

There is a check engine light. However, it came on a few months after I bought the truck (new) and two dealers couldn't find what was causing it. Since the truck was running fine and it was a problem to be without it, I didn't pay any attention to the light. In hindsight that wasn't a good move. If something (else) happened that would trip the CEL, I wouldn't alert to it.

I'll do the things that were suggested. If that doesn't work, it's a trip to the garage for a session with an analyzer. I'll post back here with what I find out.

Thanks for the help,

Tom

 

You definitely needed to mention that earlier. Find out the code and let us know.

 

Its time for new spark plugs, if it's lurching it has to do with your throttle body sensors, the iat, and tps, being dirty. If your driving and are coming to a stop and the truck is wanting to stumble or die, then it's an o2 sensor. Best bet, take the truck to a shop, and hook it up to a mt-2500 scanner and run all the sensors and have themm check the voltages, or a drbiii will work also. Spark plugs I would put @ #1 on the to do list.

 

Over the weekend, I changed the plugs. I went with the copper Autolite 3923's after reading several discussions. And I cleaned the throttle body. Man, what a difference. The problem I first described is gone. The truck feels, sounds and operates like it did when it was new. I had an adventure getting the plugs out, but that's another thread.

The condition of the plugs was "extremely worn". The center electrode was burned (?) down to the ceramic on all the plugs. I don't know if the picture is clear enough to see:



The plug on the left is the one that broke (another thread). One plug was sacrificed to get info on the broken plug (same other thread). The gap must be 3/16! I'm amazed that I didn't have more of a problem. Other than what I described in the first post, the truck ran fine.

That would be 206,000 miles on original plugs. I’ve been quite good about changing the oil and filters. Now I’ll be more diligent about the rest of the maintenance.

There were a couple of other things mentioned that I wonder if I should do. O2 sensors and a couple of acronyms I didn't recognize. What would anyone suggest on a motor with this many miles?

Thanks,

Tom