Crown Victoria-- Drop in gas mileage, check engine light

Hi all,

I have a 1995 ford crown victoria police package. 4.6 V8. Over the last two months I noticed a drop in gas mileage. I used to get close to

20mpg and now I get 15. I don't know what is up. The check engine light has been on for about a year now. My car has OBDII (yes, some 1995 fords had OBDII before everyone started putting them in every vehicle in 1996) I received P0401 Exhaust Gas Recirculation Flow Insufficient Detected. After I changed the spark plugs last week I got this error also-- P0171 System Too Lean (Bank 1). unbolted the EGR valve and check for soot but didn't see anything significant. Any ideas? Am I missing something? I have carchip so I've been able to log everythinng in my OBD2 port and reset that engine light...

Thanking you in advance

-J

Reply to
J
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Cheap, easy tip to address most likely P0171 cause: First, check your Baro reading on your car chip if possible. It should read 159 Hz at sea level driving conditions. It should read about 140 to 145 Hz if you were a mile high. I usually see 158 on a properly running Ford where I am. If the number is lower than it should be, do the following... Remove the mass airflow sensor from your intake duct. Disassemble the halves, there should be two tamperproof torx screws, and locate the two sensor elements deep inside the plastic extension that hangs down in the airstream. Clean them with electronic spray cleaner or brake clean, carefully touch a qtip to them without applying any significant pressure, blast with cleaner again, and air dry with light pressure if possible. Now go on a drive. Floor the car for a few extended runs as long as you can safely and legally. Now check the Baro reading again. See if it is higher now. If it is exactly the same, try a few more power runs. The ECM needs to see wide open throttle while under actual driving conditions to infer the barometric pressure. What you are seeing on that data list is the ECM's reported MAF frequency (to put it simplisticly) that correlates to the pressure in the intake duct when the engine is not adding or subtracting any from atmosphere (in theory). It works for Ford, but their MAF design is one that needs periodic cleaning to keep it reporting accurately.

Common P0401 cause on some 4.6, I don't know when this was corrected, but 1995 engines may still have this problem: Remove the throttle body, check the flange surfaces of the throttle body and intake manifold for coked up crud. Clean it out and make sure that the tubing/passage behind the EGR valve flows air freely as well. Then make sure the EGR VSV operates and that the EGR valve does infact open.

Toyota MDT in MO

Reply to
Comboverfish

This is a definition of the P0401 code for a 99 Taurus...should be similar for your car:

"The EGR flow rate test is performed during a steady state when engine speed and load are moderate and EGR vacuum regulator duty cycle is high. The monitor compares the actual Differential Pressure Feedback EGR circuit voltage to a desired EGR flow voltage for that state to determine if EGR flow rate is acceptable or insufficient. This is a system test and may trigger a DTC for any fault causing the EGR system to fail. The DTC associated with this test is DTC P0401. DTC P1408 is similar to P0401 but performed during KOER Self-Test conditions. "

The DPFE module (about $50-ish) is a known common failure on many fords. They get crudded up with exhaust carbon, etc...and get sick. I replaced the flex hoses too...

I suggest you get a subscription to Allldata or get a quality manual (Haines, etc)...there you should find a complete description of how the EGR works and troubleshooting procedures. I've been using Alladata for about 4 years now...pays for itself in $$$ saved every year...not counting the time and aggravation saved!

Best of luck!

--Don Byrer

Don Byrer KJ5KB Radar Tech & Smilin' Commercial Pilot Guy Glider & CFI wannabe kj5kb-at-hotmail.com

"I have slipped the surly bonds of earth; now if I can just land without bending the gear..." "Watch out for those doves..."

Reply to
Don Byrer

EGR valve on these rarely gives a problem. Too much work with too little chance of finding problem w/o doing other things first. Comberfish steered you correctly to clean the MAF and the EGR ports in the intake manifold under the throttle body.

Lugnut

Reply to
lugnut

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