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Old January 15th, 2010, 10:53 PM   #1
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Default pontiac 3400 v6 problems

well my girlfriends car has some issues and although i can do some diagnosing i still wanted to have it looked at by the pros. however two different mechanics tell me two different things. one tells me the head gasket is bad and the other tells me he thinks the lower intake gasket it bad. so id like to hear some other opinions. so before it cost an arm and a leg to fix it i would like to know for sure what is wrong with it. any help would be appreciated
runs like crap- pulled the code- reads cylinder 2 misfire
i replaced the plug first to see if it would make a difference and it didnt
the plug has power and spark but came out wet
the oil doesnt seem milky
i havent checked yet for pressure from the exhaust in the radiator
and it loses antifreeze
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Old January 15th, 2010, 11:17 PM   #2
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Being a former grand am owner (3400v6, it was a 2000 grand am I souped up a bit, stock radio rims and appearance lol), if it's the heads then usually the oil would get milky.

It seems like a LIM gasket. I would go to www.gaownersclub.com (I'm a member there and visit once in a while) and get a profile and see what the guys say. I'm pretty sure there's writeups there, you don't need any super awesome special tools, just a torque wrench and basic hand tools if I remember right.

I would also run a compression test on cyl.2 and see what it runs compared to the others... and a leakdown test as well. A blown headgasket ought to show up pretty fast then!

p.s. send me a link to the GAOC thread. Thanks!
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Old January 16th, 2010, 06:25 AM   #3
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Does the plug smell gassy? I've seen wires go bad many times, you'll get a weak spark from the plug when checking but not enough to fire the plug when it's running.

Lower intake gaskets are very common, but they normally leak externally, usually drivers side.

At this point, I see this as two separate issues. Running rough/coolant loss. I won't rule out a bad head gasket.
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Old January 16th, 2010, 06:41 AM   #4
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Old January 16th, 2010, 09:53 AM   #5
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I had to replace a head gasket on a Grand Am and it did not have milky oil.

Even if you only need to do the LIM gaskets I would go one step further and do the head gaskets as they will most likely go if they havent already and being halfway there when doing the LIM gaskets I say go for it.

Parts will be about $300-$350 iirc.

Or from what I have heard you can pick up a 3.5 from a G6, Malibu or Aura and swap it in. Then you don't have to tear the motor down just do a motor swap. And the new motors supposedly don't have the head gasket issues. The new motors can be picked up off craigslist starting at $350.

Edit: one more thing if it is a head gasket it is common for the catalytic converter to go bad during or right after a head gasket going bad.

Last edited by firehawk; January 17th, 2010 at 10:20 AM.
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Old January 16th, 2010, 07:15 PM   #6
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Does it smoke at all? Do you see any coolant leaks?

Normally if the head gasket is leaking enough to miss it will have some white smoke out the tailpipe.

I have a 5 gas analyzer at the shop and can tell you for sure if you have a head gasket leaking by checking the cooling sys. for hc's (hydrocarbons).

Check the coil for rusty terminals, also a common problem.
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