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So I figured I would ask you guys for suggestions. I recently got a 2008 Chevy cobalt lt coupe(2.2L). It has 127k miles on it and the previous own really did not take good care of it. It has lowered suspension and a cold air intake. I have already replaced the spark plugs, the air filter, the mass airflow sensor, the secondary air injection pump, cleaned the throttle body, i have put complete fuel cleaner and fuel injectors cleaner in it. And its now running fine but it still has some hesitation idling and speeding up. (The car was in pretty bad shape on the inside the air pump that I replaced was half way filled with liquid and rusted the hell out of. And the spark plugs where completely blackened and I could write my name on the throttle body with out dirty it was) what else do you guys suggested I look out? Because I don't really know what else I should work towards fixing on it. Other then maybe the fuel filter which will be a pain sense it's inside the fuel tank. And then maybe the fuel injectors. Other then that what do you guys think? Thank you for anyone that takes the time to help.
 

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I have to laugh every time I hear about a "cold air intake". There hasn't been a hot air intake since the last carbureted engine was produced. 1988? Anyway, it looks like you covered all the bases pretty good. Maybe add new O2 sensors since they are what the computer relies upon to manage the engine properly. Do you have a scan tool to see what numbers the O2 sensors are showing? Blackened plugs and throttle body- was the air filter totally plugged up? Or maybe the PCV valve is loaded with engine blowby oil?
 

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I have to laugh every time I hear about a "cold air intake". There hasn't been a hot air intake since the last carbureted engine was produced. 1988? Anyway, it looks like you covered all the bases pretty good. Maybe add new O2 sensors since they are what the computer relies upon to manage the engine properly. Do you have a scan tool to see what numbers the O2 sensors are showing? Blackened plugs and throttle body- was the air filter totally plugged up? Or maybe the PCV valve is loaded with engine blowby oil?
I don't have a scanner tool but I have had it scanned multiple times and right now the thing I'm worried about the most is I have the P0171 error. So I need to figure out how to fix that. Another thing I'm worried about is how the mass air flow sensor error keeps popping up and the secondary air injection pump error keeps popping up every time I clear it but I replaced those parts and literally had people double check it to make sure I did it right so I am worried that I might have to replace wiring which I'm guessing won't be that fun lol. And I'ma be honest I'm new to all this stuff how would I tell if the PCV valve is loaded with that stuff? But also I'm fairly sure it's because the owner before me never did any mantince and it has 127k miles on it. So that might be the reason it was so dirty.
 

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See this for the P0171 code. P0171 Code - Meaning, Causes, Symptoms (& How To Fix It) It indicates a vacuum leak but may also be other things. A clogged fuel filter/weak fuel pump can be checked by putting a fuel pressure gauge on the schraeder fitting that is on the fuel rail at the injectors. Those other new parts showing codes may be wiring issues. Where is the MAF in relation to the "cold air intake"? Was it positioned correctly? It measures the flow of air and advises the computer. But any leaks downstream from it will cause the lean condition. The PCV system directs crankcase vapors out of the engine into the intake to burned along with the fuel/air. If there is a LOT of blowby, it can upset the mixture and set a code. The Cobalt has no actual old style PCV valve. It has an orifice in the intake at the end of the hose that goes between the valve cover and intake. See it is clear and not gunked up. THIS is a bad case of blowby and means the engine is needing new rings.
When we got our '05 it kept having a lean code. It turned out that some golrilla tried yanking the air bonnet off without loosing the throttle body clamp. That cracked the bonnet and caused a downstream air leak . After epoxying the crack shut the code went away.
 

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Did you happen to perform a compression test yet? You say the previous owner didn’t care for the vehicle. So it’s also possible the engine is worn out. They are also very well know it consume oil and have piston ring issues. Also another thing that comes to mine is the catalytic converter being clogged. That can cause poor acceleration and idling issues when other things like a tune up haven’t fixed it. You’ll usually get a codes for catalyst system being below threshold.

BTW, speaking of carbureted cars, you could still get a Honda Accord in 1989 that was carbed, along with a few other models. Also the Geo Metro was sold in the US with a carbed engine up through the late 90s. Just FYI. I have an ‘87 Accord that I put a Weber carb on along with a shaved cylinder head and performance header. It was quick for what it was back then. It’s sitting now and needs a crankshaft sadly.
 

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Cody I was just guessing about when the last carbureted car was made. I am amused at what they sell to the unknowing public as a performance upgrade. Why would you buy a "cold air " intake when you already have one? And worse, something like a K&N filter that must be cleaned and oiled/replaced regularly. My daughter has a 1995 Firebird Formula. Someone added a K&N that sat where the old air filter box used to sit. It got so dirty being exposed to underhood air it was unbelievable. And a new one was over $50 when it got dirty. I yanked it out and replaced it with the factory air box with it's protected $3.99 replaceable filter. No one noticed the difference.
 

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Yeah those oiled air filters are great when clean. But you need to have a spare to stick in there for the day when you clean it, or don’t drive the car for the day until it dries out. I just change the engine air filter every 1-1.5 years or so. The cabin air filter is another story, I happen to need to change it 2-3 times a year. The humidity here makes them get really nasty.

The aftermarket air intakes work, but you only get the full potential by retuning the PCM. Otherwise it can be a very minimal power boost for most computer controlled vehicles. Some people swear by them. Fun fact, warm air supposedly gives better fuel mileage. Less power, but better fuel mileage. Seems backwards, but if you do some research with the people who try to hypermile, I believe that’s where I found the information.
 

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Fun fact, warm air supposedly gives better fuel mileage
Well, yeah. That is why the old cars had a carburetor that was optinized for operation with 100° intake air. That is the old THERMAC system. That silver tube that ran from the heated air cleaner to the hot air stove on the exhaust manifold. Then when unknowing shadetree mechanics yanked the air cleaner off they ripped the tube apart. They could not find a replacement so they figured they "don't need it". Then came the warmup and driveability problems. Nowadays the ECM is calibrated to manage the engine under all kinds of conditions. And yet people still yank stuff off that they think they "don't need" even when Engineers with masters degrees say they do. I am on a G-body website and I wish I had a buck for every guy that "yanked all that $#*! off" and then posted endless questions about why the car runs so bad. :rolleyes:
 
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