Need help diagnosing a problem with 99 sunfire

I have a 99 Pontiac Sunfire, 2.2, 4 cylinder, with 200,000 miles on it.

My problems started a couple weeks ago. I noticed the temperature gauge showed that the car was running a little higher than normal operating temperature. So I figured I was just low on coolant. I put more antifreeze and the car seemed to run at normal operating temperature for a few days. Note that when I put coolant in the car it smelled really funny when I opened the cap. The same problem came back but this time I also noticed that the temperature fluxuates depending on what I do with the hot and cold air. A few days ago when I started the car there was a significant power loss. It started fine and then when I press on the gas it sputters and takes alot of gas to get going. Today I started it up and drove it around the block and there is still a significant power loss.

Please help me isolate my problem. Thanks.

I would start by finding the coolant leak. There's a good chance that the head gasket is bad, test to confirm. For the smell, coolant needs to be flushed just like every other fluid. After the initial 5 years, it should be flushed every 2 years. When it gets old it becomes corrosive which eats away at everything in the cooling system, including the head gasket.

I would start by finding the coolant leak. There's a good chance that the head gasket is bad, test to confirm. For the smell, coolant needs to be flushed just like every other fluid. After the initial 5 years, it should be flushed every 2 years. When it gets old it becomes corrosive which eats away at everything in the cooling system, including the head gasket.

Recently I've flushed out the cooling system though so I know the coolant isnt old and corrosive.

I would start by finding the coolant leak. There's a good chance that the head gasket is bad, test to confirm. For the smell, coolant needs to be flushed just like every other fluid. After the initial 5 years, it should be flushed every 2 years. When it gets old it becomes corrosive which eats away at everything in the cooling system, including the head gasket.

If that was the first time it was flushed, I stand by what I said. Flushing it at 10 years doesn't put metal back on the head gasket :2cents: Exhaust leaking into the coolant can make it smell different too. Find the leak and fix it, then see if it still overheats. If it stops overheating when you fill the coolant, then the overheating is a result of low coolant.

Have a back pressure test done on your catalytic converter ASAP. The symptoms of raised temp, lost coolant, lost horse power, could be a plugged cat choking your 4 cylinder out.
The raised temp could cause an over heated condition, thus losing coolant.

Have a back pressure test done on your catalytic converter ASAP. The symptoms of raised temp, lost coolant, lost horse power, could be a plugged cat choking your 4 cylinder out.
The raised temp could cause an over heated condition, thus losing coolant.

How does the catalytic converter get plugged?

sure sounds like head gasket leaking.

you will get some slight temp gauge fluctuation caused by heater temp control operation. this occurs as the heater core is a heater exchanger just like the radiator and will remove heat from the coolant when your temp control is on hot. so I think that symptom is normal operation.

The fact that it is running hotter is not normal. I agree with the other post. perform a compression test to confirm bad head gasket (most likely cause of the power loss, running hot and sputtering).

Wondering if the vehicle performs normally over 30-40mph and if lack of power is just when starting from a stop. Trying to rule out a torque convertor stator issue.