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J-Man
Dodge Dakota
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4/06/2004
16:37:25
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 Subject: Vibration at Idle Problem
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Alright everyone, I was hoping you could all don your thinking caps for a few minutes, and try and help me diagnose an engine problem.
I have a '96 3.9L with 144000 km on it.
My truck runs great, other than this:
When at idle, regarless of whether the engine is cold or warm, it feels like it misses every once in a while. What I mean by that is every half a second or so you can feel a vibration. I can feel it in the stick, stearing colum, it basically just shakes the whole truck. Not really too noticable to look at, but can feel it. There is also a slight tick or tap that seems to be in conjunction with the vibration, but could just be me. Can't tell for sure. It has done this for the two years that I have owned it. Plugs were changed just a couple of months ago, new rotor and cap a year ago, just doesn't seem to fix it. I notice it a little when driving, but nothing like at idle.
Here is what I have thought of so far: Could be a bad injector? I can hear the injectors firing on the drivers side bank, but not really on the pass. side. I haven't tried "stethescoping" them yet, though. Tried injector cleaner, but hear that the store bought stuff doesn't really do anything, so it might not have helped. Could it be a bad O2 sensor? I don't know if they have ever been changed on this truck (most likely not), so they might be due, but would they cause this kind of reaction?
If you guys could help me, it would be most appreciated. I would really like to clear this up, or at least figure out what it is! I have been amazed over the last couple of weeks (since the TB posting madness) at some of the good quality questions and answers that have been showing up. Kudos to everyone on here!
Thanks again,
J-Man
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TuneUP
Dodge Dakota
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4/06/2004
21:02:22
|  RE: Vibration at Idle Problem
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clean you idle air controler, check dist cap, and wires. check plugs, clean or replace your pcv valve there are a lot of things that could cause rough idle but these are easy and if they don;t work check back with the forum.
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J-Man
Dodge Dakota
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4/06/2004
21:43:10
| RE: Vibration at Idle Problem
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Yeah,
I've done all those already, and nothing helped.
Still stumped on what it could be. I have been trying the cheapest and easiest stuff first, but I need some help on figuring out some more ideas now.
Thanks for your help, though. At least someone read throught that huge a$$ post!
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bc/canada
Dodge Dakota
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4/06/2004
22:25:30
| RE: Vibration at Idle Problem
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I have a simmilar thing going on in my 94 2wd. The vibration is in conjunction with a thump somewhere behind the dash on the drivers side. It sounds as if a solid plastic item is swinging freely and bounces/vibrates off a secured point.
Anyway, while at the dealership approx 2 yrs ago a mechanic was ouside and we were chatting. He said that his old truck was the same and it would be a $500cdn job to replace a $0.50 piece so I'm living with it as it does not affect the performance.
Sorry but I don't recall the part or location and am fully aware that this does not solve your problem.
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J-man
Dodge Dakota
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4/06/2004
23:21:59
| RE: Vibration at Idle Problem
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bc/Canada,
Where are you?
I am in BC, too. Prince George, actually.
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TOMZ
Dodge Dakota
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4/07/2004
00:54:21
| RE: Vibration at Idle Problem
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J-man, If the 02 sensor has never been replaced try that first. You need a new one anyway. Also, check your injector sinc and make sure it is at 0 or+.
If I were you and after doing these things it still happened, I'd check for arcing of the wires. Just wait till night, start the engine, open the hood and see if you can see little blue arcs in the engine compartment. You may have to actually"mist" the wires with water to find this. If this doesn,t help look for vacuum leaks, a blown plenum gasket and possibly a compression check.
I hope this helps some. LOL
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cjski
Dodge Dakota
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4/07/2004
05:10:51
| RE: Vibration at Idle Problem
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make sure no plug wires are switched...
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Bob Lincoln
Dodge Dakota
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4/07/2004
08:51:57
| RE: Vibration at Idle Problem
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"If the 02 sensor has never been replaced try that first. You need a new one anyway." Ridiculous. These should not be replaced on time intervals. Mine lasted 190K miles before failing, and it passed emissions easily a few months before failure.
Check for carbon tracking on spark plug insulators, check spark plug gap, and wire condition as described above.
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spt
Dodge Dakota
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4/07/2004
09:55:01
| RE: Vibration at Idle Problem
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Have you checked your motor mounts? If it shakes the whole truck so you feel it, sounds like it may be loose or cracked motor mount. Get under the truck and try tighting the bolts up on the motor mount. I had a similiar problem with my Ford Bronco and this was the problem. Hope this helps.
I am from Alberta, thats a nice area you live in J-man.
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J-Man
Dodge Dakota
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4/07/2004
11:30:43
| RE: Vibration at Idle Problem
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spt,
I am originally from Alberta, just here on work for 8 months. Millet, actually, just south of Edmonton.
Anyway, Thanks for the help guys.
I am pretty sure the O2 sensors are working, cause my mileage is still around 20 with a good mix of city and highway. Something that donned on me this morning is the timing chain. Could there be enough stretch in the timing chain that it throws off the timing ever couple of revolutions? I don't see how the motor mounts would make a difference... The engine vibrates and its hard enough to send it through the truck, it shouldn't matter whether they are tight or not. As long as the engine is still connected to the vehicle, the vibration is going to come through. I will check them though. Anyone know a good test to do that? Could I possibly overtighten them? Like I said, cap, rotor, plugs are all relatively new, and even right after replacement, it was still there. I am going to try tracking down another vacuum leak, but I have my doubts on that one.
Thanks again guys, this is helping a lot. Reassuring me that I have done most of the easy ones first!
Keep 'em coming though!
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dak-jak
Dodge Dakota
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4/07/2004
13:28:59
|  RE: Vibration at Idle Problem
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How about EGR valve and solenoid ?
If has not been replaced recently , may well
be acting up
95 Dak 3.9 auto 3.5 axle only a few mods so far
Ontario
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J-Man
Dodge Dakota
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4/07/2004
13:49:25
| RE: Vibration at Idle Problem
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Don't think I have one. It's a '96.
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spt
Dodge Dakota
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4/07/2004
15:51:49
| RE: Vibration at Idle Problem
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Hope this helps J-Man
If your motor mounts are cracked or loose any movement or vibration in the motor(ie rough idle, miss fires) will be amplified through the whole truck because the motor will not be kept secured to the frame and be able to move more than it should.
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J-Man
Dodge Dakota
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4/07/2004
16:33:12
| RE: Vibration at Idle Problem
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Thanks spt,
I will check those. How many are there? 2 or 4?
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93dak4x4
Dodge Dakota
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4/08/2004
11:37:58
| RE: Vibration at Idle Problem
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i suppose it could be your timing chain stretched, at idle timing could be bouncing around, mine was so loose my timing was jumping all over the place, although it never missed.. you may not have that problem with it being a 96 though....mine is a 93. the motor mount will not fix your problem though, you feel it when it misses and it shouldnt miss, so something else is wrong. if all else fails, go to carquest and get a double roller chain, i paid less then 100 for mine.
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TuneUp
Dodge Dakota
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4/08/2004
14:44:32
| RE: Vibration at Idle Problem
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Have you run a compression check and read the plugs to look for any signs of a problem??
It could also be a bad push rod they don't go out very often but is a possibility.
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J-Man
Dodge Dakota
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4/09/2004
13:16:37
| RE: Vibration at Idle Problem
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Just bumping this hoping Larry might see it as well.
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weener
Dodge Dakota
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4/09/2004
17:48:55
| RE:(Larry) Vibration at Idle Problem
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Not sure if the O2 would cause a bad idle like that or not. And since mileage is ok, they might be fine...
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Greg
Dodge Dakota
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4/09/2004
21:39:03
| RE: Vibration at Idle Problem
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I know I'm not really keen on any of this, but I would bwe willing to bet on the injectors... My truck would idle rough, never really could fix it, fuel injector cleaner would help, but durring engine tear down for the head port and polish I found out why it was running rough at idle... I never would notice it through any of the rpm range other than idle though... Come to find out my injector located on the runner where the IAT was located had leaned out so much that it had actually caused that cylinder to overheat and cracked the head right where the valve seats are... I was slowly leaking antifreeze into the cylinder causing compression to be different in that cylinder, which caused my rough idle... It would kinda miss occassionly as well, so you might want to get you a good set of injectors and see if that doesn't fix it...
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oh my god
Dodge Dakota
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4/09/2004
23:04:02
| RE: Vibration at Idle Problem
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all you guys spittin out all your crap about a problem that cant be fixed, the vibration is due to the fact that the 3.9 6 is based on a V8 and because of that there is an internal balance problem that causes the felt vibvration at idle, want is smooth, next time buy a V8 course then all you whinners will be on here wanting to know why you only get 17 mpg.
then there is dak jak that thinks magnum V6 has an EGR valve, sorry you moron, but no V6 or V8 Magnum has a EGR valve. older non magnums yes but NOT MAGNUMS
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Greg
Dodge Dakota
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4/10/2004
00:08:06
|  RE: Vibration at Idle Problem
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Actually the gen 1 magnums do have an egr valve unless I'm wrong here, which I may very well be, but the 95's down I beleive do have them...
Your v8 idle proposition is partially true as well, with the fact that the sawed off v6ers do have a slight vibration, but not one that almost seems like it's missing and I'm sure he stated to some degree that it's not always done this, which hints that there is a problem somewhere...
Oh just for your matter of fact my v6 (of course moddified) runs very smooth and will beat any stock v8 in the dakotas, except r/t's due to traction problems, i.e. no lsd or good grip tires ; ))
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