First off I would just like to say hello and thankyou to anyone who can help me with my problems with my truck. I'm new to this forum but not new to forums.*

Here's the scoop
I have been dealing with a rough idle since I bought the truck. Its a 2000 dakota 3.9l magnum engine 5 speed manual trans. 4x4 with 147k miles on it.
I will list the new parts I have installed. Some for other reasons and some to attempt to fix the idle.
New clutch
New k&n top hat style air filter(stock intake removed)
new crank position sensor
New iac(ebay cheapy my brother had laying around)
Cleaned whole throttle body
New water pump
New timing chain set with tensioner
New exhaust from collectors back
Both o2 sensors
New belt
Plugs wires cap rotor and coil
it dosnt leak or burn anything and runs smooth while moving down the road
but idling is a whole different story. When I start it cold or warm it always fires right up and idle goes to about 1k rpm sometimes alittle higher and after a few seconds it starts to make a hissing noise and the engine hemies real bad for a few seconds then the hissing subsides and it idles smooth.....until it warms up. Then it gets a loapy idle. Almost feels like it has an aftermarket cam. And sometimes the idle drops way low and it almost stalls. Never had it stall on the road. But just tonight I had it stall for the first time on me in the driveway. Drove fine after the hardest start I can remember getting it restarted. It was hissing like the start hiss the whole drive though thought that was weird. I have reset the computer a couple times when replacing sensors and such but the same p0303 misfire cyl. 3 keeps coming back to haunt me. If I leave the cel on and keep driving in the next 100 miles or less the cel will go out on its own. Then come back. I'm at my witts end with this thing. I've replaced so many parts at this point I'm just hoping to be pointed in the right direction. Thanks again anyone who can help me.

 

Sounds like this may be your problem...'New iac(ebay cheapy my brother had laying around)'. The IAC sensor adjusts the air flow into the TB. A bad one will cause the exact symptoms you're describing.

 

Ok I thought the same thing. Would that cause the hissing noise I'm hearing? And could the spark plug wires not being put back according to the tsb have any effect on this problem? Because I just read about that lastnight and it isn't exactly as they say to do it. Thanks though for all input.

 

It most definitely will cause the hissing sound if the tip if the IAC sensor is not seating properly.

When you replace it with a new one be sure to reset the PCM then start the engine letting it idle (DO NOT REV) and let it come up to operating temp then switch it off and restart.

Do you by chance have a CAI? If so, the hissing sound is going to be louder on start up until the engine warms up enough for the PCM to go into the closed lope mode and also at WOT. Just the nature of a CAI.

 

First i would like to say thank you very much for your help it is greatly appreciated bro. As for the CAI? i dont evn know what that means lol. I put in the new IAC today and i totally didnt follow your directions becasue i forgot to check the forum before i installed it. I put it in and started the truck and it was still idling bad i then took it around the block and it ran ok the idle still stumbled when i pulled it into my drive way and it seems directly related to when im moving slow and turning the stearing wheel. Dunno if that has anything to do with it. I am also hearing what sounds like either valve noise from up under the hood or possibly a spark knock even. But its only under load at idle its quiet as can be. Im gunna try reseting the ecm again and this time following your directions and see if it helps any. Thanks again for all the help!

 

wow CAI is a cold air intake lol. Im dumb! For the answer to your question is kinda. I have a tophat style k&n filter on it.

 

CIA = Cold Air Intake

Now you're starting to describe another possible issue like a blown belly pan gasket. With the engine off, remove the air hat on top of the TB, open the blades and using a flashlight look down inside the intake for excessive amounts or pooling oil in the bottom.

 

Then you are going to hear a lot of hissing from the IAC sensor with cold starts and WOT. Just the nature of the beast.

 

the belly pan gasket had been replaced at one point and when i had the tb off i looked in and there was alot of black carbon but no oil. And it consumes absolutly 0 oil from oil change to oil change. im wondering about the tsb for the coil wire re routing.

 

*Update*
I re-routed the coil wire and it wasnt even close to where it was supposed to be run according to the factory tsb. I changed it accordingly.
I then took the tophat off and flashed a light down the tb and it was dry on the bottom and all around inside there.
I then started it to see if the misfire had subsided and the idle was much better still not perfect but its got 147k on it i wouldnt expect it to. The hissing was there but alot quieter than before.
I took it for a drive and the spark knock or misfire sound is still very evident. No code yet but im thinking that maybe the spark plug may have fouled from driving with the misfire for so long(4-5months). I am letting it cool down now so i can reset the iac like you said i should've when i installed it.

One other question i have is what is the best spark plug and gap for this motor? Im running ngk's like i do in everything i own and i hear alot about autolites or something like that is the best for the engine. Its not pinging or anything with the ngk's but i figure spark plugs are cheap and ill put in the best. Thanks again bro for all the help!