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Problems and Service Talk about any mechanical problems you are having

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post #1 of 19 (permalink) Old 08-07-2010, 04:00 PM Thread Starter
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Just Bought Used Cobalt, Already Having Problems

Well, it looks like I may have really messed up. I just bought a used 2009 Cobalt LT from Herts Rent2Buy, 34500 miles. I got three things fixed before the 'bumper to bumper' warranty expired at 36,000 but now at 36,400 miles the car has begun to miss very badly. At idle it will sometimes miss so strongly that it feels like it will die, but it doesn't. And it seems that the car doesn't have nearly as much power and pep as it should have.

I took it to the Chevy dealer here and they said that the 'powertrain' warranty didn't really cover everything in the powertrain, that "a lot of sensors and other things aren't covered.' I'm very skeptical of taking a car to the dealer for repairs, they tend to just start replacing things till the problem goes away - and if the parts aren't covered, I could be in for some expensive repairs. I checked with Herts (the car has a 2000 mile warranty from them) but they say that theirs is a 'limited' warranty as well.

I have a very good mechanic here, and am considering just taking it to him to see if he can figure out what could be wrong. But before I do that, I'm wondering, is 36,000 miles too soon for plug wires to need replacing? How about fuel filter? The problem started as a little hesitation and loss of power and has turned into a bad miss. I know it could be thousands of other problems, but those are the easiest I can think of. BTW, the computer isn't reading any problems - Anyone got any ideas of what I could check myself?
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post #2 of 19 (permalink) Old 08-07-2010, 04:51 PM
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The ignition is coil over so there aren't any plug wires....check the plugs and the harnesses going to the coils. If your balt is CA emissions it won't have a replaceable fuel filter but if it isn't than it wouldn't hurt replacing it. I'd also remove and clean the throttle body (4 bolts and a harness) with CRC TB cleaner.

If the miss is bad enough for you to feel it should be throwing a random p0300 code. Are you sure it's a miss? The idle does get crappy on these cars with the a/c running and/or with a high current draw.
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post #3 of 19 (permalink) Old 08-07-2010, 06:05 PM Thread Starter
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No codes

Yeah, I thought I'd be getting a cylinder misfire code also, but nothing - the car's from Georgia, so I don't think it has CA emission stuff - My son's Honda CRX acted this way, but he was getting a misfire indication on the computer and it turned out to be plugs that weren't fully seated (!)

I've tried to watch it when it misses, and the RPM drops by about 500 for a 1/2 sec or so - it seems to me that if it were electrical, I'd see a code, right? Maybe bad gas?
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post #4 of 19 (permalink) Old 08-07-2010, 06:37 PM
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This might not help, but I know when I put my K&N drop in filter, some of the ridges got pushed in on the air intake tube running into the throtle body. I thought something was wrong with the spark plugs. I just went and pushed the dented parts out and it ran fine.
Hope this helps

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post #5 of 19 (permalink) Old 08-08-2010, 01:01 PM Thread Starter
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Well, I can certainly check that - to be honest, I haven't even opened the hood since I bought the car several weeks ago - I just went outside to take a look and it's the strangest underhood arrangement I've ever seen - I suppose all that plastic comes off fairly easily and it'll look like an engine then! :-)

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Originally Posted by bumbleninja View Post
This might not help, but I know when I put my K&N drop in filter, some of the ridges got pushed in on the air intake tube running into the throtle body. I thought something was wrong with the spark plugs. I just went and pushed the dented parts out and it ran fine.
Hope this helps
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post #6 of 19 (permalink) Old 08-08-2010, 01:07 PM
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Quote:
Originally Posted by jsm555 View Post
Well, I can certainly check that - to be honest, I haven't even opened the hood since I bought the car several weeks ago - I just went outside to take a look and it's the strangest underhood arrangement I've ever seen - I suppose all that plastic comes off fairly easily and it'll look like an engine then! :-)
LOL!! Welcome to the world of plastic engine covers!

Try cleaning the MAF -- in the intake tube between the filter box and Throttle body. Use a cleaner for MAFs (Autozone sells, for example) and make sure it's dry before reinstalling it. Another possibility is oil collecting in the PCV hole in the intake manifold. ...a little more is involved in cleaning it though -- not sure how much you know about cars -- will have to remove intake manifold.

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post #7 of 19 (permalink) Old 08-08-2010, 01:23 PM
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100k mile power/train. bring it in...IMO

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post #8 of 19 (permalink) Old 08-08-2010, 01:30 PM
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So you checked the plugs, right?

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post #9 of 19 (permalink) Old 08-09-2010, 10:44 AM
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I'd say bring it in. Some cars these days still need a tune up around your mileage. I have not check this out on the Cobalt yet, as mine is new, but take it in and see if they can diagnose something. That shouldn't cost too much.
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post #10 of 19 (permalink) Old 08-09-2010, 11:29 AM
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think about how you treat a rental car...just saying.

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