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Discussion Starter · #1 ·
Hi there,

Before I start this post, I'd like to let anyone who may be reading this that I'm both going to bed right after I finish writing this, and that I'm currently in Texas, about 950 miles from home and catch a bus towards home first thing in the morning, service will spotty and it may take me some time to get back to this thread. Please bear with me.

I just purchased a 2005 Chevy Cobalt with some issues. I expected this, as I got it for 1,000 bucks. These were some simple electrical issues, and an AC leak. All of these except the AC leak have been fixed.

Since I got the car, I noticed that Coolant temperatures get fairly high. The drive home (about 100 miles up i70 West) got the car to 220 degrees, where it entered limp mode and did not have the power to get up the hill. The check engine light came on during this time. I pulled off, let it cool to 180 and started it again. Limp mode gone, check engine light remained on. Upon reading the codes after I arrived home, it claimed P0420, Catalyst system under threshold on bank 1. This code existed twice in the system. Codes are exactly the same. Cleared the codes, replaced the thermostat. It now holds about 189 at idle and high speeds, however temps do climb when under load, the check engine light eventually comes back on and it does lose power during this time.

With that said, does anyone have any other ideas as to what might be the issue here? Car idles great, shifts great, and drives great when running at appropriate temperatures. Another issue I noticed, which may be due to the AC leak, is with the AC on, RPM's jump around between 500 and 1000 RPM at idle but performs fine when its off. AC does blow cold and strong.

I personally am suspecting Water Pump or head gasket, but I've heard it might be possible it has a very stuck pully. The car has 237,003 miles on it as of right now.

Would also like to know what normal operating temperatures are, if anyone knows.

Engine is the 2.2 litre non-turbo.

Any advice is seriously appreciated.
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