#146, "codes P0171, P0174 and P0304 LincolnLS V6"

[KevinH2000LSV6]

I own a 2000 Lincoln LS V6 with 60,000 miles that has been running rough and the service engine light has been staying on and flashing occasionaly. I finally retieved codes which are P0171, P0174 and P0304. P0171 & P0174 indicate lean condition and P0304 indicates misfire on cylinder 4. Could the misfire code P0304 be occuring due to the other codes P0171 & P0174 ? Where should I start? mass air flow sensor? It does not look like a simple task to check spark plugs and coils on the LS.

[KevinH2000LSV6]

Is it diffucult to change plugs/coils and how much time should I expect it to take? I know it involves removing the intake manifold.

[shorod]

If you are getting codes for lean condition and misfire on cylinder #4, chances are pretty good plugs and coil are not the issue. If the plug/coil on cylinder 4 was not firing, you would expect a rich condition due to a lack of spark not firing the air/fuel mixture, sending raw fuel into the exhaust. I'd suspect a fuel delivery issue such as a bad/clogged injector, restricted fuel filter, or even a weak fuel pump.

You mention the check engine light (CEL) sometimes flashes. A flashing CEL means a condition has been detected that effects the emissions. The owner's manual will suggest that you drive gently to the nearest dealership to have diagnostics performed as damage to the emission system could occur if you continue to drive the car in that state.

That being said, if it were my car, I'd start by putting a bottle of fuel injector cleaner in your fuel tank and running that for 100 miles or so with the scan tool connected in datastream mode to see if that helps.

Also, it can never hurt to change the fuel filter as that is a maintenance item anyway.

Check the condition and connections of your vacuum lines as well.

-Rod

[KevinH2000LSV6]

I had just changed the fuel filter in the last couple of months. I will try fuel injection cleaner and scan to see if that helps. I also ordered coil for #4 cylinder which should arive on Tuesday. It looks easy to change that particular coil #4 without dis-assembling everything. Thanks for the advice !!

Regards,
Kevin

[shorod]

Umm, I suggested that the problem probably isn't your coil (however, I have been wrong before ). I'd suggest not throwing away (yet) the old coil #4 in case the new coil doesn't fix your issue.

-Rod

[shorod]

I just checked the troubleshooting section on my scan tool for codes P0171, P0174, and P0304.

P0171 - System too lean B1 & P0174 - System too lean B2
Possible causes:
Stuck EGR, vapor recovery system, leaking or contaminated injectors, low fuel pressure or running out of fuel, oil overfill, improper seated oil dipstick, leaking diaphragm or EGR vacuum regulators, leaking gasket, leaking fuel pressure regulator, camshaft position timing, cylinder compression, PCV system, vacuum leak, air leaks, exhaust leaks, fuel system, excessive fuel pressure.

P0304 - Cylinder #4 Misfire detected
Possible causes:
Running out of fuel, base engine problem, evaporative emission purge valve, evaporative emission system, ignition system, fuel injectors, fuel pressure.

The only systems common to all three codes is the fuel system and evaporative emission system.

Of course there's nothing really saying that the misfire and system too lean codes are necessarily related, but is seems reasonable to treat them as if they are related.

-Rod

[KevinH2000LSV6]

I found that the air intake housing was not fully seated near the air filter. The oil change place did not put it back right after checking air filter. I changed the coil on cylinder #4 and I am no longer getting any misfire code and it now runs very smooth. I am still getting codes P0171 & P0174 and it stalls when idling. Added fuel injection cleaner. I might replace the fuel filter again. After the fuel filter change 1-2 months ago it seemed to have more getup and go, but it is a little sluggish now. I am also going to clean MAF with brake cleaner and see if that helps (read about this on another site) Any other suggestions?

[KevinH2000LSV6]

Originally Posted by shorod

I just checked the troubleshooting section on my scan tool for codes P0171, P0174, and P0304.

P0171 - System too lean B1 & P0174 - System too lean B2
Possible causes:
Stuck EGR, vapor recovery system, leaking or contaminated injectors, low fuel pressure or running out of fuel, oil overfill, improper seated oil dipstick, leaking diaphragm or EGR vacuum regulators, leaking gasket, leaking fuel pressure regulator, camshaft position timing, cylinder compression, PCV system, vacuum leak, air leaks, exhaust leaks, fuel system, excessive fuel pressure.

P0304 - Cylinder #4 Misfire detected
Possible causes:
Running out of fuel, base engine problem, evaporative emission purge valve, evaporative emission system, ignition system, fuel injectors, fuel pressure.

The only systems common to all three codes is the fuel system and evaporative emission system.

Of course there's nothing really saying that the misfire and system too lean codes are necessarily related, but is seems reasonable to treat them as if they are related.

-Rod

I had replaced the coil on cylinder #4 and I am no longer getting a miss-fire code. I cleaned the MAF Sensor, secured (wasnt fully seated in the bottom) the air intake housing and added fuel injection cleaner. After driving the last 2 days it is no longer getting any codes and is running great. The only issue I see now is stalling if I let it idle in the dirveway for a few minutes. No codes come up. Could that be idle air control? Thanks for all your suggestions Rob

[shorod]

Have you been present when the car stalled after idling? If so, did the engine race just before stalling, or sputter, slow way down in engine speed, etc.?

You may want to disconnect the battery (or pull the fuse to the PCM) for a few minutes so the computer will re-learn all the sensor parameters, etc. With as many sensor readings as you've changed (new coil, corrected air intake hose) your car's PCM may be having a hard time determining what's accurate and it will be a bit slow to adapt to correct readings.

Also, take a look at the EGR system, checking for a bad diaphragm (not sure if the LS is vacuum actuated or electrical) or stuck pintle valve. The EGR should be closed at idle. If it is stuck open, it could cause the car to die during idle, but I would expect it to also make it hard to start.

-Rod

[KevinH2000LSV6]

Originally Posted by shorod

Have you been present when the car stalled after idling? If so, did the engine race just before stalling, or sputter, slow way down in engine speed, etc.?

You may want to disconnect the battery (or pull the fuse to the PCM) for a few minutes so the computer will re-learn all the sensor parameters, etc. With as many sensor readings as you've changed (new coil, corrected air intake hose) your car's PCM may be having a hard time determining what's accurate and it will be a bit slow to adapt to correct readings.

Also, take a look at the EGR system, checking for a bad diaphragm (not sure if the LS is vacuum actuated or electrical) or stuck pintle valve. The EGR should be closed at idle. If it is stuck open, it could cause the car to die during idle, but I would expect it to also make it hard to start.

-Rod

Easy to start & idles normal for 5 minutes, then engine sputtered very briefly and stalled. Disconnected & reconnected battery, then took it for a test drive. Ran smoothly but got instance of code P0171 & P0174 again. Not sure what to look for on EGR, unfamiliar with it. EGR monitor on scan tool didnt detect any codes for EGR. Temp is only 25 degrees, would cool temp affect codes?

[shorod]

The cool temps could effect the way the car idles, and ultimately the codes. If your coolant temperature sensor for the PCM is out of range, it could be doing goofy things to your air/fuel ratio. Does your scan tool have a datastream mode? If so, with the engine cold (like after sitting overnight) hook the scan tool up and monitor the Coolant Temp reading on the scan tool and compare it to the outside temperature. If they are drastically different (like differing by more than 20 degrees) suspect a bad coolant temperature sensor.

I'm not sure if the LS uses a coolant temp sensor (for PCM) as well as a coolant temp sender (for instrument cluster gauge) or a single sensor for both. If it has two separate units, then you will need to be careful if you opt to change it that you change the correct one.

-Rod

[KevinH2000LSV6]

Originally Posted by shorod

The cool temps could effect the way the car idles, and ultimately the codes. If your coolant temperature sensor for the PCM is out of range, it could be doing goofy things to your air/fuel ratio. Does your scan tool have a datastream mode? If so, with the engine cold (like after sitting overnight) hook the scan tool up and monitor the Coolant Temp reading on the scan tool and compare it to the outside temperature. If they are drastically different (like differing by more than 20 degrees) suspect a bad coolant temperature sensor.

I'm not sure if the LS uses a coolant temp sensor (for PCM) as well as a coolant temp sender (for instrument cluster gauge) or a single sensor for both. If it has two separate units, then you will need to be careful if you opt to change it that you change the correct one.

-Rod

The scan tool I'm using does not have a datastream mode. Drove it again and got P0171 & P0174, it also stalled out twice while I was stopped with the car in drive idling

[carlos80]

For some reason Lincoln decided to put a vac. line under the intake manifold i'm almost 100% sure thats where your P0171 and p0174 are coming from, if at all possible try to spray come starter fluid under the intake and see if theres a change in your RPM. As far a a misfire reading rich shorod, it would actually register a lean condition remember the O2 sensor reads oxygen content, not fuel, a misfire would leave a whole lot of unburnt oxygen.

[shorod]

Originally Posted by carlos80

As far a a misfire reading rich shorod, it would actually register a lean condition remember the O2 sensor reads oxygen content, not fuel, a misfire would leave a whole lot of unburnt oxygen.

It depends on what causes the misfire as to whether it will lead to a rich or a lean reading on the O2 sensor. A misfire just means a cylinder failed to fire during the power stroke. This could be due to no spark or an improper air/fuel ratio.

An oxygen sensor measures the RATIO of oxygen in the exhaust with reference to outside air. If an injector is not introducing fuel to a cylinder, the spark plug will not be able to ignite the air, and a bunch of oxygen will be introduced into the exhaust stream, yielding a lean reading. Unburned fuel in the exhaust stream due to proper air/fuel mixture but no spark would yield a decreased ratio of oxygen, hench a rich condition.

-Rod

[KevinH2000LSV6]

Originally Posted by carlos80

For some reason Lincoln decided to put a vac. line under the intake manifold i'm almost 100% sure thats where your P0171 and p0174 are coming from, if at all possible try to spray come starter fluid under the intake and see if theres a change in your RPM. As far a a misfire reading rich shorod, it would actually register a lean condition remember the O2 sensor reads oxygen content, not fuel, a misfire would leave a whole lot of unburnt oxygen.

I will try the starter fluid sprayed near the intake manifold. Thanks for the suggestion. No longer any mis-fire, believe it was caused by a bad coil that I since replaced on #4