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Discussion Starter #1
Hello I'm new. I joined the cobalt family about 6 months ago purchasing an 08 cobalt lt with about 90k miles. I'm sitting at 106k today. I've started to get a misfire code P0301. I have a OBD2 tool so I can monitor stuff. I've attached 2 pictures one is while driving 15mph one is idle. Sensor one bounces like crazy at 15mph where as sensor 2 doesn't barely move is this normal?

Funny part is when I run a bottle of Chevron cleaner through it no codes runs great until my next fill up.

I've diagnosed or replaced the following.
Spark Plugs
Fuel Injectors
Coil Packs

Not sure what it could be.
Any help?
 

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You've done your plugs coil pack and injector and it still have a misfire on cyl 1? If that's the case it sounds like a burnt valve. However running chevron through it and it running perfect doesn't go with a burnt valve.
 

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Discussion Starter #3 (Edited)
Yeah that's what I was starting to get worried about is internal damage. The chevron makes the world of difference especially after 2 bottles runs like new no codes for about a week. I have no lose of power but just a rough idle when the code shows up. What something I could test for burnt valve? Compression? How hard is that to replace? I'm mechanically inclined I've worked on v8s for race cars but it's been some years.
 

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Compression test will show it.

Have you done your fuel filter? Personally I'd do a compression test and go from there, I'd check fuel pressure as well.
 

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Discussion Starter #5
Compression test will show it.

Have you done your fuel filter? Personally I'd do a compression test and go from there, I'd check fuel pressure as well.
No haven't changed fuel filter. I guess my obd2 tool doesn't read fuel pressure. I'll see what I can do about renting a cylinder compression tool. See what that turns up.
 

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If it's fine than there's something else wrong obviously but at least it's not mechanical.
 

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Your HO²s appear do be working okay and yes the first HO² is always all over the place while the second holds around .7-.8. What about your coolant is it going down? Sometimes a cracked head gasket will let a drop of coolant in the cylinder and cause a misfire since coolant doesn't burn. Wouldn't explain why it runs good on Chevron though.
 

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Doesn't necessarily mean a burnt valve but leaking valve due not seating right. Mine did the same thing at 115K miles. Drive it on a 2 hour trip 75 mph and off the ramp ran fine for several days. The valve seats were not sealing right. Could be a sticky valve, in any event a valve job did the trick. Had a low cylinder at 80 PSI,the rest around 140/145. After the work all went up to 195 psi. A compression check will tell right away. Can get one at the auto parts fairly cheap, not worth renting.

Coby is right, a bit of leaking rad fluid but if that hasn't moved since, I wouldn't go there. Fuel pressure is also no go as it would affect more than the same cylinder.

From what I've read, Valve and low compression issues related to such are common on these engines. Good fuel, frequent oil changes to get ride of the carbon absorbed by the oil and fuel additive are a must. I know that the oil change timer will go 10K , I'd change it at 5k or 50 % and spend a few $$ to avoid headaches later. You're in for some work but its doable if you have proper tools and some patience or $1500.00, expect to change your cam drive while you're at it. I wrote a post on all this.
 

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Discussion Starter #10
I'll have to find your post. I'm preparing for the worst. I'm reading up on people changing valves but not finding much info. I'm not afraid to dig in just sucks need to make sure i have all parts and tools on hand. Ill work tbrought the night as needed. Whats the total cost of a valve job gaskets and all assumin i hAve tools. I'm going to get the tester tonight or tomorrow and fingers crossed they come out ok so I don't have to do a tear down. Can't you do a test putting oil into the cylinder head to confirm it isn't pistons as well? How much oil?

Thanks!
 

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Definitely won't be $1500. If it were anywhere near just swap the whole motor. Done and done.
 

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Discussion Starter #12
Did pressure test.
Results
#1 85
#2 174
#3 172
#4 180

I have the 2.2 Ecotec is 170s and 180 normal? Anything else I can test to ensure its not the piston and rings? PSI is still holding after a few minutes now.
 

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Not good. Yes the other 3 are normal. Unless you're burning oil like crazy it's probably a burnt valve. Odd that it doesn't act up all the time though.
 

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Discussion Starter #14
Not good. Yes the other 3 are normal. Unless you're burning oil like crazy it's probably a burnt valve. Odd that it doesn't act up all the time though.
Highway I have tons of power no problems only at idle is it crap. I honestly haven't checked the oil and I'm 6k in but still in normal range. Kinda creeped up on me. I run about 500 miles a week or so changing it this weekend. I guess this means a valve job? I need to find a good article see what I should buy make sure I have it all before I start the job.
 

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Not necessarily. But quite possibly. Price up the cost to do the valves and then price up a used engine. I put a used engine into my brother's cavalier for $700 with 80k km on it.
 

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Discussion Starter #17
What can I do to make sure it's not ring related as well? I wouldn't think it would be rings just because it's holding compression right?
 
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