[Jecht]

ok here after a week or so I noticed my idle gets really rough. last sunday when I went to move my truck the idle was so rough that it was shaking the whole truck. and now it seems to like the engine is lobing at idle now. anything I can do to try and remedy this? could it be the TPS? I noticed the oil is a quart low but wouldnt think that would cause it. dont worry going to get some oil now. air filter is cleanas its a K&N drop in filter I put in this past feb. please help me. I might have to put it in the shop.

 

[kevy002]

My 03 Dak has always seemed to idle a bit on the rough side... i can feel a slight vibration... done it since new... is it normal?

 

[Jecht]

well mine has done it sence I first got it. but it gets worse at times on cold start. I am calling the dealership monday to have it checked. now its idling at almost 500. only have 30,000 miles on it.

 

[xaos]

i've had the idle problem since last summer when I bought the truck, so far this is what has helped.

amsoil ASL 5w-30 - noticed better cold starts and improved performance (moving from mobil 1 syn)
new sparkplugs (keeps idle at 650 for about 1000 miles then goes back down)
had fuel injectors cleaned
tranny flush - did nothing
cold air intake - nothing for idle
89 octane gas - Still testing but increased idle about 50 rpms and stumbles less
cleaned throttle body quickly around plate - helped the tach from moving, still a slight move in it though

When I start up my dakota it will stumble alot on a cold start (10+ hours off)
usually it will jump upto 1K+ to save itself from stalling, after this its fine. I've only has this problem during season change, during summer and winter its fine?

a note on the 89 octane gas, my parents hemi was stalling from 87 octane gas because it wanted 89 octane, my truck started stumbling around the same time, I haven't had time to test the 89 octane gas in my truck but so far it seems better. I've also read something on the 4.7L being semi hemispherical? UPDATE: Buddy Revell pointed out that the new engine is "almost" a Hemi - "the only reason it isn't called a hemi is because the combustion chambers have a wall on one side that makes it look kind of like a flat tire. Other than that everything is in the same arangment. The valve springs are across from each other and the spark plug goes right down the middle." http://www.allpar.com/mopar/47.html

next thing i'm going to do is change out the pcv valve, if this doesn't work its probably a worn out sensor somewhere.

also check your gas cap, mine goes bad every season it seems like so that could be causing a bad idle (vaccuum leak).

edit: idle only drops to 500 when tranny is engaged to reverse or drive, when the engine is still cold it will be at 650 when in drive, but as soon as it warms up it drops to 500rpm, most notably at stops when not moving, if you put it in neutral it jumps upto 650.

edit again: also there is a whine that keeps getting louder it seems from the rear, guessing its the fuel pump? possible weak fuel pump?

 

[xaos]

i've heard the k&N filters can leave a residue in the throttle body, try cleaning it.

edit: i've taken it in to the dealership twice for this problem and they have either told me the 4.7L idle rough and is normal or they can't find the problem

 

[Jecht]

well I cleaned the IAC and the TB and the idle got better. its more above 500. I would say its about 600 or so and when the ac is turned on it goes up to about 800. engine runs alot smoother now and all I can is wow never seen something build up so much carbon. will clean this every oil change.

another question is when is the PCV locared at on the 4.7 2003 model. its not in the regular spot on most engines. guess I am going to have to get a manual.

 

[xaos]

The pcv valve is located on the oil filler tube. Procedures to remove:

First disconnect the hose. Rotate the valve CCW until the locating tabs have been freed at cam lock. Then pull the valve straight out. (it should be facing towards firewall, turn 90 degrees downward)

Testing:
with the pcv valve still attached to the hose and removed from the oil filler tube place your finger over the hole and should notice a strong vaccum, also check for leaks in the hose and near the pcv valve. (engine should be idling)
*If no vaccum is felt from the pcv valve remove from hose and check hose for a vaccum.
** when the pcv valve is removed you should notice a metallic clicking noise when shaken, if not the metal check ball inside is gummed up.

that should be enough to test it, edit: tested this and mine is working fine, make sure the engine isn't to warm because the coolant lines are right above it and its a tight space to work in. (owners manual wants you to replace every 60K miles I believe)

 

[xaos]

I believe the TB is building up all of that due to an oil K&N uses on there filters. I put a cold air intake on my truck with a cone filter and haven't checked the tb since, but when I did all around the TB Plate was a heavy black coating, should check it again. When you cleaned the TB did you actually take it off or did you do what I did and just take a paper towel and wipe where the plate rests?

The 500 I believe is due to the strain on the transmission being engaged but the engine should still be able to hold the 625-650 rpm range, because I've seen it do it. when the ac is on it does go around 750-800 rpms and stays there, so the iac sensor seems to be working correctly? 89 octane gas doesn't let the rpm below 510 so far (stays at top of the 500rpm mark barely) and can't feel the motor as much. I've even seen it jump upto 625 again from 500rpm at a dead stop, so its trying but something isn't working right still.

I've heard the TPS sensor can be off from factory specs, this could explain why the idle drops to 500 because the tps doesn't sense it or gives the wrong voltage making the pcm not respond correctly. If anybody has done the tps mod and has fixed there idle from this let us know.

 

[Jecht]

I only wiped out where the butterfly rests with a terry cloth towel and carb cleaner sprayed on the towel. when I have more time I will take the TB off.

also thanks for letting me know here the PCV was located at. I would of never looked there. a wierd place to put one.