Ok.. here we go.. engine is idleing rough blows black smoke when motor is revved up..poor gas mileage.. and get 3 codes coming up..and they r PO171 PO174 and PO300.. i changed the o2 sensor on bank1 didnt help..any suggestions??..
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I had the same problem on my 2001 Sunfire (same car as the Cavalier-different branding) which I was able to fix successfully.
My symptoms were:
-Traction Control OFF light illuminated
-Cooling fan running even if engine cold and it was freezing outside (I also noticed that when the Traction light illuminated, the fan would then begin)
-Rough idle with black smoke when cold
-Poor fuel economy
I have a code reader which produced codes P0130 and P0171. These are error codes for the upstream oxygen sensor (the one under the hood).
I simply replaced the O2 sensor (it took me 10 minutes). I did not reset the check engine light after the repair as I wanted to see what the car would do on its own. The idle was much smoother with no smoke and the cooling fan stopped running unnecessarily. After 1/2 mile down the road, the Trac light went away and the system functioned normally. I tested this by trying to accelerate quickly up a snowy driveway. I also noticed that the acceleration and shifting (auto tranny) were smoother. I reset the check engine light. All is satisfactory.
What was happening to the car before the repair:
P0130 is usually for a bad O2 sensor and P0171 is the sensor detected that the motor was running too lean (but it actually wasn't-the sensor was essentially giving a false lean signal).
The rough idle, black smoke, and poor economy are due to running too rich. In my case, the sensor told the PCM (the car's computer) that the air/fuel mixture was too lean. In response, the computer said "OK, more gas!" That's why it ran rich. This was evidenced on the old O2 sensor as well...it was completely caked with carbon from an excessively rich mixture. This further destroyed the performance of the O2 sensor.
If the check engine light is on, you would need to check the computer for trouble codes first. If the engine is fuel injected, it could be a bad injector. If it has a carb, it could be a sticking choke or an internal leak.
The Effects of Over Revving a motor can be Catastrophic. I do not understand why the government would require someone to do such a test. Normal Emissions Testing is done at High (2100 - 2500) and the Idle (500-900).
Reason for Increased Smoke.... As you increase the internal pressure of the vehicle, you are creating a VACUUM and this is suckking the Oil past the rings, and anywhere else that it is causing the Vacuum.
Efffects of Over Revving van be Premature Failure of the engine (Could cost you $5-$8,000 to replace)... I would ask WHY so high... A Diesel would MAX OUT their RPM @ 4,000.
These people who are doing the test, ask them to show you where it says in WRITING 4,000... That is much higher than in the 4 states I have been certified to be an I/M Inspector
If there is a vac leak or a split in the hose between the intake and the MAF you can get a code for the sensor. The code is saying the data from the sensor is not what it should be, not necessarily that the sensor has failed. Clogged air filter or box could cause a problem too.
Hi there: Black smoke
is caused by excess fuel that has entered the cylinder area and cannot
be burned completely. Another term for excess fuel is "running
rich." Poor fuel mileage is also a common complaint when black
smoke comes out of the tailpipe. Black smoke out the tailpipe is the
least cause for alarm. Excess fuel will usually effect engine
performance, reduce fuel economy, and produce a fuel odor.
How did the fuel get into the cylinder in
the first place? Some of the causes of excess fuel are a carburetor that
is out of adjustment, a faulty fuel pump, a leaky fuel injector, or a
faulty engine computer or computer sensor. If black smoke is present,
check the engine oil as in the white smoke example to make sure excess
fuel has not contaminated it. Do not start the engine if a heavy, raw
fuel smell can be detected in the engine oil. Call your mechanic and
advise him of what you have found.
Hope this helps; also keep in mind that your feedback is important
and I`ll appreciate your time and consideration if you leave some
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Could be a idle air problem. The injector could be leaking when you shut it off ..Try some injector cleaner see if it gets better..The idle air shouldnt run rough just idle real low or sometimes it will get stuck and idle high....Are you losing any antifreeze..If you are the 2.0 SOHC engine bad about leaking antifreeze into the cylinder and makes the engine run rough until it burns it out..See if you can see the smoke coming out when it happens..White smoke indicates antifreeze,,Black smoke indicates fuel..