Missfire on Cylinder#1

[StuckAgain]

Having an "intermitent" miss-fire-ing sp? on cylinder #1
(starts and stays for a week and a half then goes away for a couple of days)

1999 Chevy Venture
86,000 miles

History:
Feb 2003:Replaced all injectors (1 went bad)

December 2004:Problem above started
Replaced plugs and wires, Plug from Cylinder1 had carbon.

Replaced fuel module (fuel sending died shorted and its not a stand alone item)
Injectors cheked out fine. New fuel pump pressure and volume are fine.

Problem went away for two days, came back.

Mechanics are stummped
They thing it may be a blown head gasket-Maybe Im wrong but there is nothing unusual in the oil or the antifreeze, and I do not believe that would cause an intermitend, non cyclical problem.

Anyone with any ideas?
Please I am all ears (or eyes)

[GMMerlin]

3 things will cause a misfire..loss of spark, fuel or compression.
While it is misfireing, you will need to determine what part of the necessary ingrediants is missing.

[rodeo02]

I would suspect a bad intake manifold gasket. You may have a crack in the gasket for the plemum that feeds that cylinder. Excess air being sucked in will cause a misfire
G/luck
Joel

[nsnell]

Any luck on getting info about this misfire on you 1999 Venture? I am having the same problem, but I think it's on cylinder #3.
Have done the plugs and wires several thousand miles ago but this problem keeps coming back. Sometimes for just a few minutes. But now it's been going on a couple of days.
Thanks,
nsnell

[dddellinger]

Any luck on tracking down the source of your problem? I have a '97 that is doing almost exactly the same thing.

[kidfam]

Originally Posted by dddellinger

Any luck on tracking down the source of your problem? I have a '97 that is doing almost exactly the same thing.

I have a 98 Olds Silhouette in which I changed the plugs a few weeks ago and it is now missing and at times the code says #1 cylinder. I rechecked the gap on the plug and everything checks out.

What did you eventually find out on yours?

[dddellinger]

Originally Posted by kidfam

What did you eventually find out on yours?

Mine turned out to be a head gasket, in the end. It probably started out as an intake gasket problem.
In talking with a friend that has a '01 Venture (and looking around on the web), it seems that the 3.4l engine is known to have intake gasket problems up until 2002 or so. The intermittant misfire is probably caused by that. It might eventually overheat (as mine did) and blow the head gasket.
It seems important to use the new GM intake gasket instead of the commonly available FelPro. I found that GM is actually cheaper than Advance Auto Parts!
I think the intake gasket swap could be done by a competent mechanic in about 4 hours or less. I'd probably add another 2 hours for the head gasket.
Hope that helps.