What does a sparatic misfire when cold started mean?

[ne0hisda0ne]

I'm sure you all know of my thread about the misfire mystery. If you read it you will know that all it was, was a bad ICM.

So that problem is taken care of, but I've noticed in the mornings lately when I first start my car and reverse out of my driveway. When I put her in 1st and push ever so slightly on the gas (speed limit 30 of course) I can hear a misfire sound, if I get on it though no misfire. It only happens for maybe 20 seconds when close to idle, but slightly giving it some gas. After the 20 seconds I never hear it again until the next morning. I was wondering what would cause a car to misfire like that, would it be my 02 sensors maybe? Would a MAP sensor do this?

[ne0hisda0ne]

Re: What does a sparatic misfire when cold started mean?

vaccuum hose, dirty intake?

[pace2006]

Re: What does a sparatic misfire when cold started mean?

Plugs or wires. Mine did this for about a month before I installed new plugs/wires. It would do it primarily on cold starts after sitting for a day or two. Towards the last few days on the older set, it started doing it on a warmer start, but would once again go away once I gave it gas.

[ne0hisda0ne]

Re: What does a sparatic misfire when cold started mean?

that can't be true...just replaced them all no less than 2 months ago...I hope it's not them...

only when cold started in the morning...when I barely give it some gas..maybe up to 1500 rpms...slight stall but sure it's a misfire....stop and do it again it may happen, may not, after that nothing...never happens again until the next morning...

was told this...

you get missfires if the car is cold and running open loop because it goes off a preset fuel map instead of using the 02 sensors to change the fuel amount.

was also told that I wouldn't even notice it on a non-modded car...but since I have ported heads that it may be why I feel it...

Since I never tuned it to begin with I may need a tune to get rid of it...

that sound right?

[Blizzard242]

Re: What does a sparatic misfire when cold started mean?

Since I never tuned it to begin with I may need a tune to get rid of it...

that sound right?

Before you even mentioned tune, that's what I was thinking. For example.. I was having a slight studder on cold starts/open loop with a slight press of the pedal. Tuned the car better and it doesn't do that at all now.

A little maf tuning would probably take care of that.

[pace2006]

Re: What does a sparatic misfire when cold started mean?

that can't be true...just replaced them all no less than 2 months ago...I hope it's not them...

only when cold started in the morning...when I barely give it some gas..maybe up to 1500 rpms...slight stall but sure it's a misfire....stop and do it again it may happen, may not, after that nothing...never happens again until the next morning...

was told this...

was also told that I wouldn't even notice it on a non-modded car...but since I have ported heads that it may be why I feel it...

Since I never tuned it to begin with I may need a tune to get rid of it...

that sound right?

I don't have ported heads or anything, so I'm not sure how a stock tune would hold up to that. If you want, here is the link to the thread I originally posted:

Misfire After Startup

Kind of a shot in the dark, but what type of plugs did you swap in?