Headgasket?

Tell us more about your air/coolant mixing theory - exactly where and how do you think this is happening?

Think for a minute about the primary ways/places a head gasket could fail. It could fail between two cylinders. The result of this would be backfiring into the intake and inability of those two cylinders to create much compression. Doesn't happen very often - I've had it happen on one car of mine. It could fail exposing the compressed charge in the cylinder to the oil return drains from head to block, or to the lifter valley. That would result in combustible mixture and/or exhaust being pumped into the crankcase. Never seen that happen. It could fail in a way where coolant is admitted to the cylinder, and where the cylinder pressure tries to pressurize the cooling system. That results usually in a lot of steam out the exhaust system, dropping coolant levels - and you can usually smell the antifreeze in the exhaust. It also usually allows coolant to get to the crankcase/oil pan making the coolant look like a mocha milkshake.

If I were in your shoes, I'd 1) pull the plugs and see if any of them look different than the others. That may give you a clue which if any cylinders are particularly affected. 2) If a plug or plugs look different, I'd run cranking compression test on that cylinder and a few others that don't look affected to see how they compare. If a cylinder(s) isn't holding up on cranking compression, then a cylinder leakdown test should tell you if it's rings, valves or head gasket that is the culprit. 3) I'd turn the engine over with all the plugs out and watch to see if any coolant gets ejected from the plug holes. That's a BIG clue as which cylinder is the offending one. 4) You can pressurize the cooling system, and see if that generates cooling leaks INTO the engine. 5) Pull the codes to see if the drivability issues are being caused by something else.

Temp. increases because of a head gasket problem are usually because enough coolant gets lost that the car overheats. If you're not losing coolant, it's possible it's still a head gasket - but if so, that type of failure doesn't happen very often, and overheating usually is not a symptom.

Not to hi-jack the thread.. but I need to run a compression test on one of my cylinders. #1 doesnt seem to be firing correctly and when I pulled the plug it looked like it had burnt oil on it.

To run a compression test, I just get a compression test tool from like Autozone or the like, pull the plug in the offending cylinder and hook the tool up to the cylinder, unhook the coil and crank the engine correct?

Sorry again to hijack.. =]

Also hold the throttle wide open when cranking. However, that won't tell you much without testing some of the ones you think are normal too for comparison. I'd pull all eight plugs and check them all. Also makes it easier on the starter/battery when turning things over.

Perhaps your fan clutch took a dump from vibration due to a balancer that's going bad. Is the balancer wobbling or does it have any of the rubber cracked or looking like it's squeezed out from between the rings?

Temp climbing at idle usually simply means that not enough air's moving across the radiator at low speeds = fan, if all else is well. Generally, head gasket would cause worse problems as revs climb. What kind of temp gauge? If stock, they're worthless. Perhaps you've got a bad balancer and a gauge sending unit that is about to bite it.

Have you pulled codes yet?

check the thermostat. mine did the same thing, it may be sticking

I prefer to use coolant from the car since that's what the t'stat operates in; and I use a thermostat so I can see when it begins to open, and at what temp it's open all the way. I always test t'stats and temp. switches before using them.