Hey guys, I'm new here. My names Jake. I currently drive my parents 1998 Durango with the 5.2 in it. Anyway, they bought it brand new off the lot, and my dad has really taken care of it. Oil changed every 3,000. You cant tell its a '98 its that clean. Well, lately its been not running the same. On cold start it seems a little hesitant to fire over. It seems like the starter has to crank longer than it used to. Still starts ok, but about a minute or 2 after running it will start idling rough. Damn thing sounds like its running a cam!! I gave it a rev to make it stop doing that and my friend said there was some blackish smoke going out the tailpipe, maybe running rich?? Things that have been done..currently has 102,000 miles
Dodge installed a new intake man. gasket around 30k
I believe my dad changed the dist. cap but im not sure. Plugs were done at 75k. Wires are original. The fact that they're original makes me think they are causing the misfire. And the gas mileage is...well its horrible. 11.7mpg on a highway trip
But the thing is, once it's warmed up she runs like normal, except for the nasty gas mileage. But the gas mileage for a 14 yr old 4x4 truck with an old tech engine is what i'd expect. But with the pedal to the floor, it really has nothing..at all. I know it used to haul more *** then it does now. What should we replace?

 

Pre-cat O2 sensors are most likely for the bad mpgs. Also check the IAC and TPS on the throttle body and give it a good cleaning, here are the instructions https://dodgeforum.com/forum/1st-gen...ttle-body.html
I would also do the plug wires, that should have been done with the spark plugs but whatever.

 

start with a tune up, new plugs (copper core champion plugs ONLY), cap, rotor, wires (MSD or mopar performance 8mm wires or better)
plugs are a 30k mile part btw.

if that doesnt take care of it check and clean the throttle body and IAC motor(valve, its located on the back of the throttle body) for the bad gas mileage i would look into the pre cat oxygen (o2) sensor, it controls A/F mixture, you should be able to get 12/13 city and 15/16 highway out of it, or at least closer to it than you are.

 

Sorry to but in, but I just did a tune up on my '03 R/T and I used these: http://www.ngk.com/more_info.asp?AAIA=1413122&pid=3021

Why do you say copper core Champions only?

 

Just cause other people have destroyed (not exaggerating here) these engines using other brands. I myself use E3's and they work great. I haven't had a set of champions last 2000 miles so I gave up on them but other members have had great success with them. My dad has always used ac delco's with great success but those were in gm vehicles.

 

champion plugs are the factory equipment(and the cheapest option i have seen for these trucks), and for a stock motor run the best out of all the brands and types of plugs offered in these engines. most copper core plugs will work acceptably for a normal tune up, but when diagnosing a problem, or trying to get back from a poor run condition it is best to use the original equipment replacement parts.

The NGK vpower plugs are supposed to be designed to create the spark near the outside of the ground electrode (2 sparks say for simplicity sake) however it doesnt(ok it might when they plugs are BRAND NEW, but once they wear in the slightest bit they function as a normal, slightly more expensive plug), this is because the electricity will follow the path of least resistance, the shortest gap between the electrode(center) and the ground, nice way for the company to make extra money at your expense.


adukart, the e3 plugs are another scam, they dont improve anything, they simply spark from the shortest gap between the electrodes(similar to the multi prong plugs that only spark from one of the 3+ prongs once they start to burn/wear in), good way to waste money (almost as bad as tb spacers) but NOT a good way to get any performance of efficiency improvement.

 

Your right on the lack of performance gain, but I noticed a huge difference in cold starts at -20 to -40 below.

 

let them wear in i promise any gains are VERY temporary

 

The IAC valve went bad a few years ago, maybe around 80k miles, im not too sure. The throttle body is spotlessly clean. Another thing it does which is probably a misfire, if i accelerate without letting it warm up enough, i can feel it hesitate and stop accelerating even though im on the gas pedal, and it starts buckin and clunkin..let off the gas and it fixes itself.
Weird thing is, the check engine light never comes on.

 

If the O2 sensor is bad, wouldnt the CEL come on? Im guessing it is the tune up that it really needs. Cruising on the road though, I cant feel it miss, cut out or nothin. Only when its not fully warmed up it will sputter.