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Discussion Starter #1
Hey YC just wanted to know if anyone else has experienced this? I have a 2010 LT with 56k on it I got a Cel and hard shift going into 2nd more so when car is hot. light is on all the time. tried remove neg batt cable to clear code and with in 5-10 miles cel comes back. Taken it to get read and showed misfire cyclinder 3 check gas cap and also abs system disabled. Only thing my car has is a Hid kit with relay. I changed cyclinder 3 coil pack and spark plug and new gas cap....Thinking it might be an injector......Any help or suggestions??? No I have not went to dealer or mechanic yet. Had cel read at autozone. Thanks in advance


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What was the code or codes?
 

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Tyme516

Let me know if or when you would like to go to the dealer. I can locate one in your area. Unfortunately I am not a technician and can't answer your question but I am here to offer direction and answer other vehicle questions. Just let me know by private message if you need my assistance.

Jackie
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Discussion Starter #4
Coby it was a p303 if I'm not mistaken I misplaced the paper!


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---------- Post added at 08:19 PM ---------- Previous post was at 08:18 PM ----------

Thanks Jackie if I can't resolve on forum ill pm you.


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---------- Post added at 08:37 PM ---------- Previous post was at 08:19 PM ----------

Coby sorry I know it helps if I had the codes but the paper is mia. Definitely said it was the cyclinder 3 misfire gas cap and abs disabled. I've read through the forum and did as others did re: plugs first then coil pack, new gas cap. 99%sure the hid kit would not cause the mis. I do appreciate any insight into this. Thanks again for the help Coby and YC members


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Great. Just let me know. I will be here. Hopefully you can find an answer here on the forum.

Jackie
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Okay, I don't want to down what others said that led you to do what you did, but You didn't eliminate anything with the method you chose. Let me explain. By changing the plug and coil for new ones might sound like a good idea and we all assume that new means it is going to work for sure. We all know that ain't true. Now unless you kept the old parts you can't go back. So I'm going to write this for others that might have the same problem. What you need to know is which part is defective so instead of putting in new parts at random and think you eliminate that piece automatically, here is what you need to do. Since pistons 1&4 work or cycle opposite each other and 2&3 do the same what you should have done is take the plug from cylinder 3 and switch it with a known good plug like 1 or 4, this way after clearing the code and P0303 comes back you know it's not the plug. Then do the same with the ignition coil, if the code comes up P0301 you know you have a bad coil, if it comes up P0303 again you leave it cause that means all your plugs and coils are good and you haven't spent a penny yet. Next move on to injectors and do the same switch injectors between 3 and 1 or 4 , P0303 comes back you have eliminated all these parts at no cost yet leaving you with ECM continuity between coil and ECM connectors. Clean connectors and test again. After all this if P0303 is still present you move on to compression test.

---------- Post added at 10:28 PM ---------- Previous post was at 10:13 PM ----------

By the way for some unknown reason when ECM loses cam-crank correlation for a fraction of a second and doesn't know if it's a faulty crank sensor or faulty cam sensor it sets P0303 code on 07-10. GM techs still don't know why according to bulletins. If it fails for longer, then of course it will give a crank or a cam code. Just so you know.

---------- Post added at 10:33 PM ---------- Previous post was at 10:28 PM ----------

My guess you will find that light blue wire on pin "23" of "P2" rubbing on a metal surface somewhere between ECM and ignition coil #3. Just a guess.
 

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Discussion Starter #7
Hmm lot of info lol I still have old parts but as u said spet $ on plug and cpack. Ill check the wires as u said and move on from there. Thanks I will keep u posted


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Update;
Went to mechanic did compression test, 1,2,4 have 225 cylinder 3 has 150. He said the intake gasket is leaking. @coby does this sound correct?


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---------- Post added at 05:53 PM ---------- Previous post was at 05:52 PM ----------

Covered under powertrain warranty?


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No, but head gasket would. And yes this would be covered under powertrain warranty.
 

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Discussion Starter #10
Thanks coby always there to lend a hand! Always appreciate your help and also all the other YC members! Ill keep you posted. Also sent Jackie from Cust service a msg regarding the above along with dealer info.


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So what did they find?
 

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A burnt valve would do it but these cars aren't known for this problem.
 

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Yes, I have not read anything on that either. The only thing I did was put premium gas in for about a month. Car seemed to run smoother with it than with regular. Tech said to only use regular using the 93 instead of 87 is most likely what caused it. I drive maybe 300 mi per week. 250 for work and 50 local.


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---------- Post added at 04:15 PM ---------- Previous post was at 04:13 PM ----------

I know an hid kit would not contribute lol I was getting some interior dash flicker while installed so I had taken them out. B4 the issue came about.


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High test gas caused a burnt valve? That sounds like a steamy pile of bull to me. How would premium cause a problem? It's not like our cars are recommended to use 87 like the turbo is recommended to use 93. Right?
 

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Discussion Starter #19
Kmac The 93 burns hotter right? I have not the slightest clue like I said I should be getting the paper work in the mail prolly Monday so I will know exactly what was done. I did not see the tech when I picked the car up. I called and asked if it was ready and they said they were just finishing up. I went an hour later and a service rep brought the car around to me and I left. Said they would mail it instead of having me wait for it.


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I found this online and this guy put it much better than I could but confirmed what I suspected.

Nope, not hotter, faster, slower, or any of the things that our local mower repair man keeps telling my co-workers.

It is merely more resistant to self igniting in the presence of pressure, temperature, and hot spots.
But the I found this in the same forum, which seems to be the exact issue.

Some cars had warnings years ago on running high octane fuels as they were set to use regular. The reason given was burning exhaust valves. This was not due to higher temps but to a slightly longer burn time that produced a hotter exhaust gas that caused the exhaust valve to run hotter. My wife's Saturn has a warning like this in the owner's manual and I think Buick may have had it as well.
And this:

There is no correlation between octane and burn speed. Some high octane fuels burn slower (some aircraft blends), some burn faster (car race fuels). Burn rates are a byproduct of whatever gas mix a refinery kicks out of the pipeline that day. As mechtech2 pointed out, the burn rate has no noticable effect on chamber pressures (unless you get into F1 RPM territory, but by then octane ratings are largely inconsequential).

Octane rating is no indication of "energy content" or heat produced by a fuel. Alcohol has a high octane/performance number, but has lower energy content and burns slower.

All one can infer from an "octane rating" is a fuels resistance to detonation. Any other qualities (energy/heat production,burn rate, cleaning ability, etc) are independant of that.
Here's the site where I got all this info, it was an interesting read.

Does premium unleaded burn hotter than regular - Bob Is The Oil Guy
 
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