2000 Sunfire losing engine power

[mrplane12]

Over the past couple of weeks my girlfriend's car has been gradually losing power. Yesterday I looked into it and found that two of the plugs were completely shot, the electrodes completely burned out. New plugs didn't do it, the idle improved, but still no power. At that point it would rev to about 3500 rpm, then bog down. When matted it would nearly stall out. Today it got worse, it can only run about 2500 rpm and you can only run about 1/4 throttle. My first guess was the catalytic converter, so I pulled it off and gutted it. Nope. So, I decided to run the codes and it said misfire and O2 pre cat O2 sensor. We replaced the O2, but that didn't help either. I moved on to check the compression and it was 195 in all four cylinders. Not sure where else to go from here. The spark is good in all four cylinders as well. Wires are new. Gas mileage is horrible, I'm talking 10 mpg bad. The check engine and service lights are on, but not blinking. I feel like there's a constant rattle in engine and it doesn't seem to be a loose heat shield or anything. All the fluid levels are good, but it is running a little warmer than usual. The car has never run super since she's owned it. About a year ago her timing chain was replaced by a novice and it's had an erratic idle, but good power until now. Could the timing chain have jumped? Any other ideas? Thank you

 

[brothergc]

Over the past couple of weeks my girlfriend's car has been gradually losing power. Yesterday I looked into it and found that two of the plugs were completely shot, the electrodes completely burned out. New plugs didn't do it, the idle improved, but still no power. At that point it would rev to about 3500 rpm, then bog down. When matted it would nearly stall out. Today it got worse, it can only run about 2500 rpm and you can only run about 1/4 throttle. My first guess was the catalytic converter, so I pulled it off and gutted it. Nope. So, I decided to run the codes and it said misfire and O2 pre cat O2 sensor. We replaced the O2, but that didn't help either. I moved on to check the compression and it was 195 in all four cylinders. Not sure where else to go from here. The spark is good in all four cylinders as well. Wires are new. Gas mileage is horrible, I'm talking 10 mpg bad. The check engine and service lights are on, but not blinking. I feel like there's a constant rattle in engine and it doesn't seem to be a loose heat shield or anything. All the fluid levels are good, but it is running a little warmer than usual. The car has never run super since she's owned it. About a year ago her timing chain was replaced by a novice and it's had an erratic idle, but good power until now. Could the timing chain have jumped? Any other ideas? Thank you

You say "a rattle in the engine" ? Is it coming from the harmonic ballencer area ? When the chain was replaced did he replace the tenshioner as well . Yes a timing cain could be the issue and that what I would look into next

 

[Zimgxp]

Check the fuel pressure.

 

[mrplane12]

Thank you for the ideas. Also, would a bad battery cause this to happen? It will crank a few times and start, but it's nearly dead and doesn't hold a charge. I'm not sure if Pontiacs are designed to run off of the alternator only. I know with my 99 Civic I can disconnect the battery and the car will still run fine off the alternator. What do you think?

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[julianotourville]

i also have a pontiac sunfire and i had a similer problem so i replaced the battery and it dident help i replaced the plugs and it dident help so i gave it a full tune up wires plugs airfilter every thing so ever time it lost more and more powere and then it started smokeing and i put it in the shop to see what was going on, i had a blown head gasket went to advanced bought new head gaskedreplaced it and while i was in there changed thermostat and water pump through on a new belt changed the oil about 3 times and now it runs like a champ and doesent miss at all hope this helps.

 

[Zimgxp]

If the compression is good and even across the motor, it probably isn't a head gasket.