Change spark plugs (Good enough?)

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  #1  
Old 11-19-07, 09:05 AM
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Change spark plugs (Good enough?)

2003 Nissan Altima
107,000 miles

Service engine soon light came on.
Went to Auto Zone and got:

P0302
Misfire in cylinder #2

Probable causes:

1- Ignition system fault-spark plug(s), ignition wires, coil
2. Vacuum leak
3. Injector fault
4. High or low fuel pressure

So...I decided to change my spark plugs (which I haven't done yet though) and pour in some injector fluid.

Do I or should I change the coils? Are the coils the same as ignition wires?

What's a vacuum leak? I've recently had an oil/filter change at one of those oil/filter places and they check for leaks...I had none. Does that have anything to do with the vacuum leak? Meaning...I shouldn't worry about it?

What's # 3 and 4? What are ways to know if I have to worry about these as well? And... what are the solutions?
 
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  #2  
Old 11-19-07, 10:33 AM
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It's probably more likely to be the wires or coils than plugs, but the plugs are the cheapest. Ignition wires, aka plug wires, run from the coil(s)s to the plugs; they are a preventive maintenance item, so if they are original, probably wouldn't hurt to change them regardless of whether they are the casue of the current problem. The engine creates vacuum in the intake manifold during operation; that's how the fuel/air mixture is drawn into the cylinders. The manifold has several fittings on it from which a small portion of this vacuum is used to actuate some other components and for sensors, etc. A vacuum leak is usually a vacuum line that has come off a fitting or has split or there is a bad fitting. Often the fittings are plastic and can break. Finding a vacuum leak can be a challenge. You can start be listening for it; a vacuum leak will often cause an audible hissing noise. Side note: Fuel pressure regulators are often vacuum controlled. Might be a good place to start looking.

Injector fault would be a generic term meaning the injector might not be functioning properly. Would need a scanner to run that down.

High or low pressure - more likely low - self-explanatory; the fuel pressure is above or below optimum. Too high could be a faulty pressure regulator; too low, clogged fuel filter or failing fuel pump.

Nissan??? Thought everyone in California drove Porsches.
 
  #3  
Old 11-19-07, 10:37 AM
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I'd replace the ignition wires along with the plugs.

There are a lot of thin rubber lines that connect different sensors and such. A vacumn is pulled thru these lines to operate the different sensors - if a line gets loose, cracked or plugged up it won't allow whatever device it is hooked to, to operate correctly. they are usually fairly easy to replace, just pull off the old ones [one at a time] and replace with new.

New cars don't have carborators, they use injectors to pump fluid into each individual cylinder. If an injector is partial clogged or the fuel pump not delivering the correct pressure it can affect how the engine runs.

Tune it up, put some good fuel injector cleaner in the tank and check/replace vacumn lines first - those are all the cheaper things
 
  #4  
Old 11-19-07, 11:17 AM
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Wow. Thanks guys.

...I meant...my Porsche!

You guys are talking as if I know her! (My Altima). Sad to say...I don't. Before I can understand your language... is there a diagram of some sort you guys can point out to me so I know where all these parts are? I've got my manual, but it only shows so much. I've got the idea on the spark plugs but that's about it.

...and I thought the spark plugs were expensive...I can't wait to find out the cost of the rest of the stuff

Ah...found the coils...is this it?

http://www.autozone.com/R,APP34688/v...ductDetail.htm

If I pop open my hood...I'll see this right?
 
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Old 11-19-07, 12:01 PM
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Originally Posted by DIYaddict View Post
Wow. Thanks guys.

...I meant...my Porsche!
Person I work for has a mint condition, never driven in winter, Carrera.

You guys are talking as if I know her! (My Altima). Sad to say...I don't. Before I can understand your language... is there a diagram of some sort you guys can point out to me so I know where all these parts are?
If you start unscrewing it and water starts coming out, you are undoing the wrong part.
 
  #6  
Old 11-19-07, 01:11 PM
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Can't say for sure from here, but I'd bet real money it just needs new wires and plugs
Regardless, it's time for new ones anyway so it's a no-brainer...change them

I'm pretty sure your spark plugs are accessible from the top of the engine, but they are deep enough inside to need socket extensions or a special really long socket

Don't forget the anti-seize paste on the plugs threads, and dielectric grease on the plug wire connections/ends
 
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Old 11-19-07, 01:21 PM
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Okay, if that's your coil type, you won't really have plug wires. What you'll see is the top portion of that coil pack assembly (the end with the connector plug on it) sticking up out of the top of the valve cover. To get to the plugs you would unplug the coil pack, remove the retaining bolt and pull up on the pack to remove it. Down in the hole you'll see the spark plug(s).

I wouldn't go replacing the coil packs (@ $70 a whack or so) unless I knew one was bad for sure.

Here's some interesting reading for you:

http://www.nissanforums.com/a33-2000...l-failure.html

Possible warranty work if it's coil pack(s).
 
  #8  
Old 11-19-07, 01:58 PM
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misfire

first off you need to know if engine is still misfiring, it could have been only once or twice but thats enough to trigger sensor and store a tbc ( troublecode ) on computer, anyways, if its still misfiring it will most likely be the coil pack for that cylinder. I wouldnt worry too much about wires or spark plugs, even though if plugs never been replaced before it would be a good idea to do it now, but modern engines can go that long and even longer with original spark plugs, no sweat, carbuteror's fouling plugs days are over, or so i hope
 
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Old 11-19-07, 02:18 PM
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I think it's BEEN misfiring. Can't say for sure. I had SES light come on before (a month ago?...can't remember). I didn't have the code for it yet and after poppin' open the hood and checking (looking) around, the light went off so I ignored it.

Call me nutto, but I just realized the code (TBC?) said "...cylinder #2". Does that mean I'd only have to replace 1 of them? Are they labeled or something? (Yes...I know nothing about cars but how to put gas in it and drive it ). Either way...I should be replacing ALL of them? I just confused myself...

I think it's time I look in my records to see what I have had replaced and what I haven't. At this point, I don't think anything's been replaced, but who knows. I just pay the mechanic. I'm on my own for now. At least my records will be a start before deciding something right? If I just had my spark plugs changed, at least I can go return what I bought and get the other stuff.

BTW: TG...thanks. Except, I read that and it's on Maximas?
 
  #10  
Old 11-19-07, 02:31 PM
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Originally Posted by DIYaddict View Post
Call me nutto...
Well...Okay..."nutto"

 
  #11  
Old 11-19-07, 02:53 PM
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coil pack

well if you've been driving this car you'd notice right away if it's still misfiring, lack of power, poor mpg, engine just not running smooth, you can tell right away more so on a 4 cyl engine, and yes you'd only have to replace the coil pack for that specific cylinder, # 2 in your case.
Now if it is not misfiring anymore just play it by ear, sometimes engine will have a misfire under hard acceleration, not really a big deal if it happens only once or twice , you dont notice it but the computer does.
 
  #12  
Old 11-19-07, 03:05 PM
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Thanks slick...har har har. (I admit, I'm a nutto sometimes though!)

Fergot to mention it's a 4 cyl.

I do believe I feel something. MPG is good. I can't really tell the "power" thing b/c I mostly drive in traffic. But I can tell my RPM's weird. Does that have anything to do with it?

Thanks for the explanation on the specific cylinder. It's starting to make more sense. I think I'm going to play with the pedal here and there and see what happens.

I just wanted to make sure I'd be safe for a couple days before I get my hands on the issue.

Would saying "If it ain't broke, don't fix it", apply here? Or shall I just change all of them while I'm at it?
 
  #13  
Old 11-19-07, 04:23 PM
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swap coils

Swap coils from #2 to #3 and see if code now shows misfire #3 cyl.
 
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Old 11-19-07, 04:37 PM
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Hey! Good idea!
 
  #15  
Old 11-19-07, 07:06 PM
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Doh!

Just got home and it's probably, most likely not the spark plugs b/c I just had them replace this past January

Fuel injector was put in...and the car feels GR8! ha ha...well...that or it's just a mental thing.

Definitely going to return the spark plugs and look into the coils.
 
  #16  
Old 11-19-07, 07:06 PM
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You might just need to push #2 coil/wire back in there...it may just be loose (it's supposed to be tight on the spark plug in there, but you can't see it really, you've just got to push down, make sure it's tight)
 
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