Question about 2005 Chevrolet Cobalt
I have a 2006 Chevy cobalt with around 53,000 miles on it. I have intermittent misfires, When I start it, my rpms drop down to zero and only have the bells and whistles ( radio, lights etc.) I do not have a check engine light come on. In the past I have had a lean fuel code and the computer was reprogrammed and so far that has been fixed. What could be my problem. the car always starts after a couple of tries and it seems like weather changed affect it, the warmer it is the more often it misfires. please help!!
I can think of a couple of possible things to check.
When is the last time you put in new spark plugs? Ever? Check them. The problem may simply be worn out spark plugs. Likewise, a bad spark plug cable could cause misfires. Yet that is rather unlikely considering your car's low mileage.
Check the connections of all of the rubber vacuum lines which are attached to the top of the engine and which then are attached elsewhere. A vacuum leak due to loose fitting connections can make it hard to start the car. Likewise a vacuum leak can also cause the lean fuel code since the intake manifold no longer generates as strong of a vacuum as it should.
Virtually all cars have a Positive Crankcase Ventilation (PCV) valve located somewhere on the cylinder head cover. The big rubber grommet around the PCV valve is a common cause of vacuum leaks. Check that the PCV valve is making a snug fit inside of this rubber grommet. While you are at it, pull the PCV valve out of the grommet and make sure that it isn't stopped up. A stopped up PCV valve is very unlikely if you have been good about regularly changing your car's oil.
Check that the clamps for the big hose running from the top of the engine to the air filter housing are snug. And, of course, check that the air filter isn't extremely dirty or stopped up with debris.
It is possible that the mass air flow sensor is defective or has gone bad, but I highly doubt this since your car has very low mileage. Besides, a bad mass air flow sensor on any modern car should produce an error code.
A dirty fuel filter or a weak fuel pump could cause starting problems, and might even cause stalling and misfire problems -- especially when driving uphill. Yet I don't think that this is the problem. Just something to keep in mind as a possibility.
It is possible that the ignition module is either defective or has prematurely gone bad. Usually a good sign of the ignition module going bad is an increasing rate of misfires as the engine gets warmed up. Start the car and let it idle and warm up. If the rate of misfires increases as the engine warms up to normal operating temperature, then it is likely that the ignition module is close to completely giving up the ghost.
Finally, make sure that all bolts connecting the intake manifold and air bell atop the intake manifold are tight. Again, the idea is to get rid of vacuum leaks. This is unlikely, but worth checking. These bolts should never be tightened more than the specified torque values.
Well, these are just some common things which should initially be checked. Assuming that the spark plugs and plug wires are good and considering your car's low mileage, I am betting on either a vacuum leak or a failing ignition module. The latter can be tested by a mechanic who uses an oscilloscope to look for missing ignition module pulses.
Posted on Apr 20, 2009
Aveo misfire sometimes when idle or running with the ac on,new spark plugs is installed
Posted on Jun 16, 2009
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Posted on Jan 02, 2017
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