Slight Sputter on Cold Start

[MattB]

On cold (<40 degree) mornings when I start my G20, it will sometimes sputter slightly (<1/2 second) as it comes on. It will also from time to time rev to about 1550 or so on cold start in the morning, quickly down to about 1000, and then quickly back up to 1500 with no sign of an impending stall. There is no other hesitation or anything in the engine. It doesn't do this at any other time of the day, not even when I start it in the late afternoon to go home after having it parked all day. Once warmed up it'll easily go to 5000rpm before shifting, and would go higher if I pushed it. I'm having the car in for some service on Wednesday anyway, so is there anything I should have looked at that could cause this problem? Bad tank of gas maybe?

[elwesso]

I would say maybe the slightest injector leak???

[HeavyDuty]

Since you're going in for service, check to see when the last time you did the obvious tune up stuff (cap, rotor, plugs, wires, fuel filter, pcv valve)

IMHO, have the throttle body serviced, and since you're already right there anyway by that point, clean the egr tube (the large tube on the exhaust manifold that leads up to the throttle body via the EGR valve). There's a very small passage that leads to an AIV valve and they get clogged with gra-doo over time. Just a pipe cleaner & carb spray will get it. Also, there's a cold start bypass underneath the manifold that takes metered air & lets it bypass the throttle body when cold. If it's broken, it stays in the shut mode and the AAC/IACV valve has to work harder to maintain idle. If a combo of this stuff is in need of service/replacement, it can make for a very cold natured SR20.

[MattB]

I would say maybe the slightest injector leak???

Wouldn't that manifest itself on more than just a cold start in the morning though?

[elwesso]

It could just be leaking the tiniest little bit that it floods the cylinder... It wont leak enough for hot start....

[MattB]

That makes sense, but my car only does this in the morning. After 7 hours in cold weather during the day, it never does this when I start it to go home in the evening.

[elwesso]

Hmmm... maybe its that with the cold weather..

Id like to hear some other input on this.....

[MattB]

An Infiniti tech told me that it may be a bad IAC valve. It makes sense considering how much salt, sand and other stuff is on the roads around here-the thing could easily get jammed. The temperatures at night also drop into the low teens to (at worst) negative numbers, so I think something may be getting affected by the extreme cold.