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http://www.youtube.com/watch?v=bFxmoyO3OZg -p0171
The adaptive fuel strategy in the vehicle’s computer constantly monitors the fuel delivery system to make sure the engine is running at an optimum air to fuel ratio, which is 14.7:1. The computer adjusts injector pulse width to regulate the amount of fuel going into the engine. The oxygen sensors relay information to the Powertrain Control Module (computer), informing it of the oxygen content in the exhaust. This information is translated by the computer, and used to determine if more or less fuel is needed. A P0171 check engine light code is set when the computer has reached a rich calibration limit and can not add enough fuel to maintain the correct mixture. Try cleaning the egr.
Possible Causes: 02 sensor???
Fuel System:Leaking or faulty fuel pressure regulator
Plugged or dirty fuel filter or lines
Fuel pump weak or defective check valve
Injectors leaking or faulty
Low fuel pressure or running out of fuel
Leaking EVAP system components
Faulty FRP (Fuel Rail Pressure Sensor)Air Intake System
Vacuum leaks
Contaminated, damaged or faulty Mass Air Flow sensor
PCV valve leak or stuck open
Air induction turbulance caused by wrong filter
Oil dipstick not seated
Air leaks after the Mass Air Flow Sensor (MAF)
Oil coated aftermarket air filterExhaust System
Any exhaust leak before or near the oxygen sensors
EGR System
Vacuum line disconnected from EGR System Module (ESM)
EGR valve, tube or gasket leak
EGR vacuum regulator valve leakingSecondary Air Injection System
Mechanically stuck secondary air injection valve
P0304
http://www.youtube.com/watch?v=XF3f4EaL59kThe misfire detection monitor, a software strategy built into the computer, is designed to detect an engine misfire. The computer can also normally identify the specific cylinder in which the misfire has occurred. A misfire is nothing more than a lack of combustion, which can be caused by poor fuel quality or metering, low compression, lack of spark or unmetered air entering the engine. There are other possible, less obvious causes as well, such as uncommanded Exhaust Gas Recirculatin (EGR), flow. When the misfire monitor detects a misfire, it will trigger the check engine light with the specific cylinder number as the last digit in the P030X code. For instance cylinder 1 misfire is P0301, cylinder 2 is P0302 etc. In this case we are left with a P0304 in the computer memory.Possible Causes: Fuel injectors, related wiring, sensors and computer issues
Running out of gas, or poor fuel quality
Evaporative emissions system (EVAP) concerns: fuel vapors leaking into engine
Incorrect Fuel Pressure
EGR system concerns: leaking EGR valve or restricted ports
Base engine concerns: low compression, valve train problems and timing issues
Ignition system concerns including, but not limited to:
Faulty spark plugs
Faulty coil or related wiring
Ignition module or related wiring issues
Ignition related sensor faults or wiring issuesTurns out you can’t even buy the PCV hose for these cars. Great. Gonna try piecing something together..
you can use a piece of heater hose the same size. take the hose to the auto part store and replace the whole thing. C8-)
good call. gonna do that tomorrow.
the fuel filter wasn’t REALLY clogged (i’ve seen worse) but the stuff that i blew out of it was pretty black and filthy looking.
The engine is running lean, and you are getting a misfire on #4, I’d take a close look at that injector. If it’s restricted or plugged then that would cause the PCM to add fuel to compensate. Can you listen to it using a stethoscope (or the screwdriver trick) and verify it sounds like the others?
Car starts much easier with a clean fuel filter, found a big honkin’ leakin the PCV hose. Case closed.
In would be looking for a vacuum leak, particularly around the PCV valve/hose as that’s a common issue on those vehicles.
Eric has a video on checking for vacuum leaks without the use of a smoke machine –
http://www.youtube.com/watch?v=9CPqbaSg … h5ma49U%3D
I would also recommend stress testing the ignition system on cylinder 4 as well as using a noid light to check the integrity of the injector circuit as well as PCM driver activity. The stethoscope suggestion above is also excellent to see f the injector solenoid is energizing or not.
You also may want to check for adequate fuel pressure, KOEO and KOER, maybe adding a volume test also.
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