2005 3.5SE - Cold start question, possible issue?

[Llarion]

Hi there!

My 2005 3.5SE runs great; but in the last 30-60 days, I've noticed an odd behavior. When the engine is dead cold, the first start of the day or on the way home from work, it has to crank longer than it used to, like 1.5-2 seconds. It's like it's hesitating for a second before catching. Once it has run, even for a minute, it the catches immediately, like brand new. I did a B&G gas additive at the last oil change to remove water from my fuel system; my regular mechanic suspected it might be that; and that did indeed help but only for a couple of days. It's almost a non issue because it always starts, but it's different enough from that way it behaved for 6 years that I'm a little suspicious.

In thinking about what else it might be, I came up with the following hypotheses:

1) Fuel pump failing - when cold, it's taking longer to get it "primed" than it used to, so perhaps the pump is weakening but still functioning.
2) Ignition system - dirty spark plugs, perhaps, or a weakening ignition coil; but it seems like a problem like this would either manifest all the time, or even be a binary state (run/not run at all) in the case of a coil going bad.
3) Intake plumbing - I change my air filter regularly, but could the intake system be somehow gummed up in such a way that it would impact cold starting?

I'm under a really good extended warranty; it's essentially the factory warranty with a $50 deductible, but before I take it to the dealer; I wanted to have some learned opinions, since the problem is so minor as to possibly escape detection. I'm "retentive", so I notice. And I'm a little paranoid that if it's the fuel pump, that it will one day just strand me; so I wanted to head it off at the pass proactively.

Any thoughts or insights would be greatly appreciated! Thanks in advance!

[Llarion]

UPDATE - I think more and more it's the fuel pump; as an experiment, when I got in the car to come home from work; I turned the key to ON and then waited 3-4 seconds before engaging the starter, and then it fired instantly. It's like the fuel pump is needing to prime itself and is taking longer when cold... Any thoughts? Anyone? Bueller?

[DrewH]

I've always been in the habit of giving my car a few seconds after I turn the ignition on. I'd recommend that to anybody since it does give the fuel pump time to build pressure.

How many miles are on your car? It's probably a safe bet to say that if you're rolling around with the original plugs that you should definitely change them. I changed mine at 75k and immediately noticed a difference in the way the car idled/ran. You'll be happy to know that Nissan made that process ridiculously fun.

I would start with that. As far as the fuel pump goes your mechanic should be able to check your fuel pressure to see if it's not pumping at the correct psi. Super simple thing to check and it only takes a couple seconds.

* when my fuel pump died it just plain ol' quit. Fine one day and then the car wouldn't start the next.

[Llarion]

I'm at just over 60K, and yes, it is on the factory plugs. I lost a fuel pump in my 95 Passat, and it was a binary state too... Run, then no run. Is there a particular plug you recommend? And is it safe to assume that by "fun", you meant "ridiculous, unless I know how to defy physics..."

Thanks!!!

[Llarion]

Oh good lord, just saw a how to guide for that; that's WAY past my equipment and ambition level...

[DrewH]

Yeah it's a real treat. Somebody at Nissan is still laughing. I'm impressed by your low mileage but if you plan to change plugs I would recommend either the original NGKs or iridium NGKs. How's your oil consumption?

[Llarion]

I have never once had to even top it up. It's freakish. I change it every 2500-3000 religiously. The times when it's been "yeah, maybe it could use a little", it's been time to change it anyway. It's been the best car I've ever owned by a big huge long stretch. It's worst mechanical failures have been a busted motor mount and one of the A/C hoses let go once, and the stereo ate itself one time. All under warranty. It has a healthy appetite for tires and brakes (My commute to work is 10 miles, 17 stop lights, on Florida pavement which has shell in the aggregate which makes it rough), I'm on my 4th set of tires (just got em, I get 20K out of a set) and 2nd set of brakes (needed fronts at 35K and rears at 45K) It has been as trouble free as I think anyone could ever expect a car to be. On the plugs, it says 100k change interval so I guess I could understand them not having to make it easy.

[DrewH]

Yeah that 100k interval is a joke. It'll run alright but like I said with 25k to go I noticed a difference immediately. Still on your original battery?

[Llarion]

No, got 3 years out of that, bought a DieHard Gold with a three year warranty, and it went at 2y 10mo so I'm on a pretty fresh battery.

[DrewH]

Well based on what you've said that leaves a possible, yet I believe to be unlikely, fuel pump issue or I'm thinking this is an injector issue. Not that something is wrong with them but believe when the car is cold something is interrupting the pulse operation. If you had water in your tank/lines you would have gotten a blinking SES misfire code and if it was enough water the cars performance would be noticeable affected. It's more likely that they and/or your lines could be gumming up a bit. This is a downside of low mileage because fuel isn't pumped as often as normal and particulates are allowed to settle and collect. I would run another fuel system cleaner through before your next oil change and if it doesn't help I would do it again. Just my .02.

[Llarion]

I had one done at the last oil change, and it did actually make things smoother for about three days so it stands to reason... What about the fuel filter? Would that affect things? I don't think thats been done.

[DrewH]

Prepare to scratch your head and wonder..... our car doesn't have one.

[Llarion]

You're kidding!!!! So, the injectors just take the hit if something foreign gets into the fuel??

[DrewH]

There's a unserviceable filter in the tank that you would change when you replace the pump. It's not as fine of a filter as the inline ones of the past but apparently most people weren't changing them enough or at all.