hello community. this is my first post and believe me i have done my research here before starting this thread. ok here goes i have a 2000 dodge durango r/t with the 5.9 engine. i just bought it 1 month ago and i paid $3100 for it it has 155000 on the odometer and it needed a lot of work. so far i have changed the following parts due to a cylinder #1 misfire and very rough idle. the tps, iac, pcv valve, distributor cap and rotor (brass) plug wires 7.5mm oem, #1 fuel injector, air filter, cleaned the throtle body and iac port real good. had the battery tested (2 years old) good quality battery. the first set of plugs were denso's then i found the forum and found out that the champion copper was the right ones so i changed them but still the engine is running rough not quite as bad but not as smooth as i would like! by the way i have reset the computer as per this forums instructions serveral different times after sensor replacements and still problems.. after restting the computer no check engine light yet and the idle is a bit smoother but i have a feeling it will come back on.. i also have checked for oil by looking down the throtle body and it is dry. i have sprayed carb and choke cleaner around looking for vacum leaks and found nothing.. i have only ran premium gas since i bought it and have used fuel injector cleaner a few times i also had the mechanic check out the fuel injector wiring and everything is good there.
this is the only problem "rough idle" it runs pretty good as soon as you press the gas and pulls real good with no back firing and starts right up no stalling and shifts right.. my question since i just changed the plugs today and it is running a little better will the computer take a few days to "relearn and adjust to smooth out the idle?

 

This has been a problem with the 5.9 motors, Replacing the spark plugs, cap and rotor, wire set and the lower intake manifold gasket. The problem you may have is either a burnt valve or a crack in the head between the intake and exhaust valves. Sorry it maybe time for a tear down and inspect.

 

update: with addition of new champion copper plugs and resetting the computer the durango ran better for a few miles and cold starts but now check engine light says code p0303 i believe thats cylinder #3 misfire soooooo what now? can this be a clogged cat or 02 sensors causing these misfire situations?

 

If the cat was clogged that engine wouldn't run very well. Perform a compression test on all cylinders and post the readings.

 

today i was able to work on the durango and i changed the #3 plug for a new one (champion copper) and made sure the gap was right the plug i took out looked decent nothing too dark nothing too grey looked pretty normal to me. i also took the plug wires off anf returned them to advance auto they gave me a brand new set the wires are 7mm not 7.5 like i thought, they are autolite pro http://shop.advanceautoparts.com/web...072#fragment-3
the reviews on the wires are good and i dont think they are my problem but i just wanted to make sure possibly my wire routing job is the problem but i think i would see arching at night in the dark? i guess i will take mastertechs advice and do a compression test on all the cylinders. i have to find out if i can rent the tester at autozone or advance auto. i have never done that before i assume that you take the coil wire off so the truck does not start then take the plug out and screw in the gauge and crank it a few times and chart the highest reading for each cylinder? am i right here? somebody help me i think i bought a money pit!!!!

 

Are you only swapping one plug, not a full set?

 

when i first got the d about 1 month ago it was running rough and threw the cylinder #1 misfire so i put new plugs in it they were densos i put all 8 plugs and then i joined the forum and since then i have changed all 8 plugs to champion coppers as suggested then i was getting cylinder #3 misfire so i changed the #3 plug with a new champion copper and put brand new wires on still the same problem rough running and cylinder #3 misfire i will check the compression to all cylinders but i cant do it til this weekend i will post the results when i get them

 

I dunno if the 360 has the same issues with spark hop that my 318 did, but (esp in really hot summer days, and even on brand new wires) if I ran the wires in the factory wire runs down the valve covers on my 318, I got some severe spark hop on 5 and 7. Found out that there was a TSB to re-route the wires, actually running one over the transmission fill tube. After I did this, my misfire and spark knock/hop went away.

Might try inspecting that #3 wire the entire length, and look for white spots along the casing to see if you're getting spark hop to other wires or to ground. Might also reach up inside the wire boot on the plug side with some needle nose pliers, and kind of gently tug the end clip down a little. The plugs on the 318 and 360 are well down inside the head, and I had problems a couple times with the wire "feeling" like it seated on the plug end, only to actually slide up a little and end up making contact only on an edge. Esp after I went to using diaelectric grease on my plug wires (cause you don't usually get that satisfying "snap" when that clip goes over the end of the electrode). When this happened, it would idle well, and seem fine. The code would even clear, and all would be ok. Then I would get in, and part throttle the truck, and it would knock, I'd set a code, and go through it all over again. It wasn't until I inspected the boot of all 8 wires that I found the end clip rolled up into the top of the boot, looking like just the side was touching the electrode end. As soon as I pulled it down, and reseated it, all was well.

This very well could not be the case, but, just a couple little suggestions to look at while you're doing your compression test (since you'll have that wire off anyway, might as well make sure your not over-working yourself for a gremlin that could be easier to trace down).

 

thanks for the suggestion and i will take a look at that this weekend when i do the compression test. i am going to the scrap yard and i am going to pick-up a few things for the D like the ashtray i am missing and the rear window trim piece that is rusting and sending streaks down my hatch door and bumper. while i am there i am going to grab a fuel rail and all 8 injectors and clean them and the rail and place those on the truck and see what it runs like hey you nver know i may have rust in the fuel rail or something but as long as i am there i am going to get as many parts as i can i am also going to grab the pick-up coil, map sensor, and temp sensor.

 

personally i wouldnt trust sensors i found in the junkyard