Poor Running Cobalt...Questions?

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As xxch4osxx stated, the after-cat O2 sensor doesn't really do anything except monitor the cat efficacy. If you think it's causing trouble you can get a $5 part on Ebay called a spacer or extender. It threads into the exhaust and the O2 sensor threads into it, pulling the sensor out of the exhaust stream and fooling the computer so it doesn't throw a code. Much less expensive than replacing the O2 sensor or the catalytic converter.
 
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Yea, why all the calls for replacing 02 sensors etc. when the code is for the MAP sensor??? To diagnose the MAP sensor, start the car cold and wait for it to warm up and go into closed loop. When it starts acting up, unplug the MAP sensor which will trip the computer into open loop limp mode. If it instantly runs better, you know it's the MAP sensor.
 
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Originally Posted By: Drew99GT
Yea, why all the calls for replacing 02 sensors etc. when the code is for the MAP sensor???
I was wondering the same thing.
 

FFeng7

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Here's the update to my Cobalt. I installed a new set of plugs and it did not not cure the problem. The old plugs were probably just fine but new ones were fairly inexpensive. I finally got the new map sensor in yesterday and installed it yesterday evening. On the Ecotec the throttle body has to be removed in order to install the MAP sensor. While I had the throttle body off I gave it a good cleanig. It was actually quite dirty probably from the previous owners cold air intake setup and Spectre air filter. I reassembled everything using the new MAP sensor and disconnected the negative battery cable to hopefully clear the check engine codes. So far the Cobalt is running great today. It did have an elevated idle for short while. The people on the Cobalt forums say this is normal after cleaning the throttle body as the computer learns the idle as the throttle body is electronically controlled. So far I believe it to have been a faulty MAP sensor that caused the poor performance. Thank you all for the help.
 
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Originally Posted By: artificialist
Ignition coil packs are a common failure point on Ecotec engines. Waste spark means that cylinder 1 and 4 spark at from one ignition coil circuit, and that cylinder 2 and 3 spark from the other ignition coil circuit. This suggests to me that you need all new ignition coils and boots.
I too was thinking coil pack. This happened to my daughters 2011 Chevy Cruze. Seemed to run fine then at highway speeds it would sputter. Dealer found a cracked coil pack and was replaced under warranty.
 
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