I have a 2001 Dodge Dakoda that has started running rough. I’ve installed new plugs, with no improvement. It also idles rough, and will stall often. My gas mileage has also dropped by five miles per gallon. I’m thinking it may be the throttle position control may be defective. Am I looking in the right direction?
Scanning for codes is a good first step because guessing is going to get very expensive.
Any Check Engine Light on? What did the old spark plugs look like; black and sooty or clean and tan in color?
Just grabbing something out of the air based on no info, what about a leaking fuel pressure regulator? Remove the vacuum line and see if there’s fuel in it.
Have you replaced the fuel filer recently? That could be an easy and cheap fix if is clogged up.
Correction fuel filter (fat fingers) 
I doubt it is the throttle positioner. It might be a hundred and sixteen different things. How about having it checked to see if you have any CEL codes stored. If so post them back here. Some auto part stores will read them for free. Just get the codes not an interpretation of what it means. They should be in the format of “P1234”
Also how many miles on your car? Has it had regular maintenance performed as listed in the owner’s manual? How long has this been a problem?
Thanks for your reply. I do plan on having the codes checked on it, just haven’t been able to get to shop. Also, I failed to give all the information on the problem. The truck has 130,000 mile and has been serviced regularly. It seems to lug down too low in speed before it shifts down out of overdrive. And the idle rpm has dropped by about 200 rpm. This problem started a few weeks ago. When I changed the plugs, they were black and sooty.
Check engine light was lighted for a few days, but then went out. The plugs were black and sooty. I do plan on taking it to shop for a code reading. Just needing more information so I will be more informed.
Didn’t think about fuel filter. I will check it for sure. Thanks
Add a new air filter onto that list. Did you do the plugs only or wires too? I’d probably do wires as well - esp if they are the original ones.
A 9 year old car may also need new park plug WIRES and other electrical components. Have the entire electrical systme checked out as well as the fuel delivery system; injectors, etc.
The black sooty deposit is dry carbon deposition. That comes from an inappropriately rich fuel mix. An inappropriately rich fuel mix sometimes comes from a faulty fuel pressure regulator (pressur etoo high), but more often comes from a failed sensor. Prime candidates are the upstream oxygen sensor, the mass airflow sensor, and the temp sensor. But there are other possible causes.
As others have stated, attempting to guess before having the stored fault codes read could be expensive and futile. Post the codes here and we’ll advise you on where to look.