What causes a car to stumble and tries to quit but it just takes spells doing this? I get a P0171 and P0300. I have already replaced the fuel filter, air filter, mass air flow sensor, and cleaned the throttle body with throttle body cleaner. It runs better but still same problem and still same codes. Anyone have any suggestions on what to fix or check?

P0300 - random misfire , P0171 & P0174 lean code's . All of this means you could have a bad vacuum leak ,low fuel pressure ,clogged fuel filter , Mass air flow sensor problem .
Ford 150 P0171 P0174 Trouble Codes vacuum leak water test
Low fuel pressure causing P0171 and P0174 trouble code

code p0300 refers to random/multiple misfires--misfire detected===causes--spark plug/sHT leads--injectors--ignition coil/s---low compression---wiring
code p0171 refers to system too lean, bvank 1===causes--intake/exhaust leak--AIR system--fuel pressure/pump---MAF/VAF sensors---injectors---HO2S sensor
The common thread is fuel so have a pressure test done on the fuel system to check for pump and / or faulty pressure regulator, then progress to injectors.

do u have a oil leak are u putting cheap oil

p0300 is a misfire code. have you replaced the spark plugs?

P0300 Diagnostic Code - Random Misfire
Technical description:--
Random/Multiple Cylinder Misfire Detected:---
Exactly what does this code means:--
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:--
the engine may be harder to start.the engine may stumble / stumble, and/or hesitate.
other symptoms may also be present…There may be rough idle, sputters and stallsand jerks.
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 for this error problem:--
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 vehicle, 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 un-metered air getting past the airflow sensor, or an EGR valve that is stuck open.

Fuel Sys, Driveability, Filters (Air & Fuel)
2006 CHEVROLET COBALT

02/01/2006 ELIMINATION OF FUEL FILLER TUBE FLAPPER DOOR 03/01/2006 ERRATIC FUEL GAUGE READINGS 06/01/2006 USAGE OF E85 FUELS IN GM VEHICLES - REVISED 06/01/2006 L61 ENGINE MALFUNCTION INDICATOR LAMP (MIL)/SERVICE ENGINE SOON (SES) LAMP ILLUMINATED WITH DTC P0171 "FUEL TRIM SYSTEM LEAN" SET 07/01/2006 TOP TIER DETERGENT GASOLINE - DEPOSITS, FUEL ECONOMY, NO START, POWER, PERFORMANCE, STALL CONCERNS - REVISED 07/01/2006 USE OF E85 FUELS IN VEHICLES NOT CERTIFIED BY GM AS BEING FLEX FUEL COMPATIBLE / AFTERMARKET CONVERSIONS OF VEHICLES TO OPERATE ON E85 FUELS 09/01/2006 397.pdf&btitle=2006 CHEVROLET COBALT&yr=2006">GM FUEL SYSTEM TREATMENT PLUS, FUEL SENDING UNIT CORROSION AND FUEL SYSTEM DEPOSITS - REVISED 11/01/2006 940.pdf&btitle=2006 CHEVROLET COBALT&yr=2006">ERRATIC FUEL GAUGE READINGS - REVISED 03/01/2006 USAGE OF E85 FUELS IN GM VEHICLES - REVISED 12/01/2006 TOP TIER DETERGENT GASOLINE - DEPOSITS, FUEL ECONOMY, NO START, POWER, PERFORMANCE, STALL CONCERNS - REVISED 01/01/2007 EMISSION RECALL - ENGINE FUEL INJECTORS - REPLACE 01/01/2007 LSJ, L61, LK5, L52, LL8 ENGINE - REDUCED ENGINE POWER, MIL/SES LIGHT, DTC P1516, P2135, P2138 02/01/2007 MULTIPLE DRIVEABILITY SYMPTOMS DUE TO CLOGGED FUEL INJECTORS, MIL/SES DTCS P0171, P0172, P0174, P0300, P1174, P1175 - REVISED 03/01/2007 MULTIPLE DRIVEABILITY SYMPTOMS DUE TO CLOGGED FUEL INJECTORS, MIL/SES DTCS P0171, P0172, P0174, P0300, P1174, P1175 - REVISED 05/01/2007 MULTIPLE DRIVEABILITY SYMPTOMS DUE TO CLOGGED FUEL INJECTORS, MIL/SES DTCS P0171, P0172, P0174, P0300, P1174, P1175 - REVISED 06/01/2007 <A href="http://arrc.epnet.com/autoasp/data.asp?sid=122357497&uid=s9193090.remote.autorefctr&type=pdf&ff=082000

P0171------ system too lean bank#1
Po174------ system too lean bank#2
For these 2 codes, try cleaning the maf sensor (mass air flow), that is mounted in the big black hose that goes from the air filter housing to the throttle plate, if it is dirty, that will cause those 02 sensors to send a signal to the computor to lean the air fuel mixture. If cleaning it doesn't work, the sensors will probably need changing.
P0300---- Random/multiple cylinder misfire
P0316---- Cylinder misfire at start up---- first 100 revolutions.
On those 2 codes, you have to do some testing to find out why there is a misfire.
Possible causes:
dirty/malfunctioning injectors
weak coil pack
fowling spark plugs/wires
Low fuel pressure

HI
P0300 is multiple misfires.
P0171 is lean burn on left bank 1 means drivers side
02 sensor is faulty. Your vehicle is over fuelling that is why your are getting P0300 code and the rotten egg smell. Good idea is to replace both 02 sensors.

A P0300 code is a random cylinder misfire code and could be caused by a bad plug, plug wire, or fuel injector. The P0171 is bank one o2 sensor is reading lean w/ both of these combined could mean a vacumm leak.. Hope this helps.

the p0171 code is for a fuel system lean code......possible causes are a cracked exhaust manifold.....bad o2 sensor...bad coolant temp sensor fuel pump.....lean fuel can cause the other codes you have for misfires