2005 Chevy Impala problems.

[thx997303]

Well since everybody else seems to be soliciting help for automotive problems, I figured I may as well.

Two things. 2005 Chevy Impala.

Doesn't run well at initial startup. Usually takes two attempts to start, then runs like it's got two cylinders for about a minute.

And the other thing, it loses antifreeze extremely slowly. Usually ends up too low to properly cool after 6 months. The notorious manifold gasket has been replaced with the updated metal gasket, so that likely isn't the cause.

I'm thinking the heater core may be weeping, as I occasionally smell antifreeze when using the heater or AC, but I have found no leaked coolant in the cab, and that smell is rather intermittent.

[Hickory]

Could be a blown head gasket leaking anti-freeze into cylinder
causing it to run rough until anti-freeze burns off.

[geargnasher]

3.8L engine? Sounds like coolant seeping into the cylinders on shutdown to me. First thing I'd do (since I have the tool) would be do a coolant pressure test when the engine is cold, see if it loses pressure. Also, you can pull the spark plugs out after sitting overnight and see if there is any moisture on the electrodes. It will be obvious if there is. Some of the 3.8L plastic intake manifolds themselves were an issue, warping underneath the throttle body where the upper intake seals to the aluminum, lower intake. The 3.1 and 3.4 engines have a different design. The EGR passage has two coolant ports next to it, and the coolant will leak across into the EGR, and thus into the intake, on shutdown causing issues like you have. IF your car has that style of intake and engine, the fix is to replace the upper intake plenum with a redesigned Dorman unit, available through O'reilly autoparts and some others. That fixes the warping problem.

I've fixed a lot of intake jobs, so just because the gaskets have been replaced doesn't mean they aren't leaking!

Gear

[44deerslayer]

You could also do a compression test will tell if it is a head gasket if it's not a head gasket look at the water pump weep hole.the water pump could be bad

[thx997303]

The engine is a 3.4

I'll do a compression test when I figure out where my tester got to.

[firefly1957]

Check the short hose above the water pump for a pin hole leak even though it is under the hood you will smell it in the car at times. It is no fun to pull them rear plugs put a bucket under the exhaust at start up a little water is normal in cold weather but if there is antifreeze in it you have a problem.

[Fishman]

I have a 2000 impala with the 3.4. Have you put in new plugs and wires lately. I got a deal on mine with 93k on it several years ago and a tune up fixed all that. Intake gasket leaked, yes. They can determine if the head gasket is leaking quite easily with a simple test.

[thx997303]

New plugs and wires a few years ago in TX.

[GabbyM]

Those engines have a habit of needing a manifold gasket replacement. About every 100,000 miles.
My GF has one sitting in a Pontiac with a thrown rod from hydro locking. Any Chevy mechanic will be familiar with the issue. You’ll need a good fender blanket to keep from scratching the paint as you’ll be leaning over the thing for a couple hours.