I would check the PCV elbow hose to the side of the throttle body for being collapsed and leaking. The code 300 is for a random miss fire, which, if the PCV hose is leaking could cause that code.
P0171 - System Too Lean (Bank 1)
Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.
Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.
You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.
Causes: A code P0171 may mean that one or more of the following has happened:
* The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
* There could be a vacuum leak downstream of the MAF sensor.
Possible solutions include:
* In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
* Inspect all vacuum and PCV hoses, replace if necessary
* Check for a dirty fuel filter and proper fuel pressure
About P0300, basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.
A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.
Symptoms may include:
* the engine may be harder to start
* the engine may stumble / stumble, and/or hesitate
* other symptoms may also be present
Causes: A code P0300 may mean that one or more of the following has happened:
* Faulty spark plugs or wires
* Faulty coil (pack)
* Faulty oxygen sensor(s)
* Faulty fuel injector(s)
* Burned exhaust valve
* Faulty catalytic converter(s)
* Stuck/blocked EGR valve / passages
* Faulty camshaft position sensor
* Defective computer
Possible Solutions:
* If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
* If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.
Test the O2 sensors and keep us updated.
Have you checked to see if the injectors aren't getting any electrical
pulses. My guess would be that the ignition is to blame and not fuel pump. on that
particular engine, the crankshaft position sensor can do exactly what you
are describing, and cause the fuel pump to not work, and also a no spark
condition.
Next time it dies, check for spark if you see there isn't any spark, it's
ignition related. Possibly computer related.
I hope this helps.
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The P0171 and P0174 are running lean codes. The P0300 is multiple random misfire I would maybe do a tune up. Try new spark plugs and wires. But the idling problem also sounds like your throttle positioning sensor is not functioning properly. But should have a code of P0121. But a tune up could even fix the idling problem.
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I'm just looking for a second opinion for comparison.
The rough/erratic idling occurs every time I start the engine after it has been shut off long enough for the engine to completely cool down, but the codes are intermitten. once the engine has warmed up, the erratic idling stops. I have cleaned the mass airflow, and removed the EGR valve and it seems to be operating as it should.
Thank you for the additional infor...I will check that.
Yes the injectors seem to be firing ok. I change the downstream O2 sensor and the P0171/P0174 codes have not came back. Now, all it seems to do is have a very hard time finding idle when started first thing in the morning or when starting after sitting all day. It goes down to approximately 500 rpm, sounds like it is just barely keeping from dying, then increases up to almost 2000 rpm, then back down. It will do this several times before it finally settles in. what baffles me is it will only do this after sitting overnight, or for the 10 hours I'm at work. It won't happen if it has only been sitting for 3-4 hours.
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