2005 Mercury Monterey poor gas milage

Tiny
DON22
  • 2005 MERCURY MONTEREY

Engine Performance problem
2005 Mercury Monterey 6 cyl Front Wheel Drive Automatic 75000 miles

I had the fuel pump replaced, and gas milage dropped 3 miles per gal. Eng analizer say mixture is to rich. Mech reset fuel air mix, but the fuel mixture resets itself to a rich setting after car is restarted. I had it reset again, and drove the van 60 miles and got 25.4 MPG. I stopped, shut the engine off, restarted the engine, and retraced the same route. Gas mileage dropped to 20.4MPG. Mech does not know what to do. Help

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Wednesday, August 19th, 2009 AT 2:05 PM

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Tiny
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Hello -

Can you tell me your engine size in liter and the 8th digit of your VIN?

Sensors that affect an engine to run rich are manifold air temperature sensor, engine coolant temp sensor, O2 sensor and the intake air temperature sensor. Excessive fuel consumption can be a faulty engine coolant sensor.

Have you tried pulling the codes to see what codes are thrown?

If you want to do this yourself before taking it to the mechanic. You can go to Auto Zone (AZ) or O'Reilly's (OR) and for FREE they can pull the codes to the car. Most important: Once they check your codes, if they find something and you don't get it fixed and need to get back with us, please make sure you tell us exactly what the code was, number and all. Example, if the code was E0568 O2 Sensor bad. Then make sure you give us all of that. While there for FREE also they can bring their tester out and check your battery and alternator.

I can advise you on the codes if you receive any. The common sensor for running rich and fuel consumption is your engine coolant temp sensor.I would have that checked out.

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Thursday, August 20th, 2009 AT 12:01 AM
Tiny
DON22
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The eng size is 4.2L. The 8th digit is the #2. I will do as you suggest

don22

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Thursday, August 20th, 2009 AT 8:41 AM
Tiny
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Why would the computer reset itself after it was adjusted to lean the fuel out.

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Monday, August 24th, 2009 AT 9:20 AM
Tiny
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Hello -

There can be several reasons. It can be resetting (which it appears it is) once the key is cycled (on/off) Sometimes the check engine light can come on and once you cycle the key it goes off. The code is still there but it resets the light.

Obviously it is reading a sensor or something that we need to figure out that will keep it from resetting.

Once you do go to AZ or OR and they check the codes. Again, make sure you get all the info on it if it gives codes. The code number, what they say it is etc and give that to me. When they have done that have them clear all codes.

Let me know what you find.

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Monday, August 24th, 2009 AT 10:52 PM
Tiny
DON22
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I had the analizer hooked again last night, and there are no codes. I am going to replace the eng coolant sensor.

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Tuesday, August 25th, 2009 AT 8:42 AM
Tiny
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Hello -

Please let me know what you find out after the replacement

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Tuesday, August 25th, 2009 AT 9:28 PM
Tiny
DON22
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After replacing the cyl head temp sensor, I drove 2 days, 300 miles each. The AC was off, and cruise was on. Speed was 70 MPH, on 4 lane road. Gas milage was 21.8 first day, and 21.2 the second day. The route was the same both days. It seems that the temp sensor was not the problem. There is no eng code.

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Thursday, August 27th, 2009 AT 10:15 AM
Tiny
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Hello -

Well. We still aren't there BUT. It is a little better. Only a little but that is a positive.

Have you had the mass air flow sensor checked and or the Intake air temperature sensor checked?

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Thursday, August 27th, 2009 AT 10:47 PM
Tiny
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Hello -

One last note..........try cleaning the Mass Air Flow sensor with some electrical cleaner. Go easy.


http://www.2carpros.com/forum/automotive_pictures/248015_6_23.jpg


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Thursday, August 27th, 2009 AT 11:07 PM
Tiny
DON22
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I wrote down some reading's from analizer. At idle, 640rpm the eng load is 19%, with a/c on load is 23%. The eng temp reads 16,800 F. The timing reads 22 to 24 degrees. Air sensor, O2 sensor, egr sensor, all check ok. A few of the injectors show they stay open periodically a little longer then the should. Timing and eng load seem high to me. The eng temp used to read 30,000 F before sensor was changed. I also noticed on this last trip that I now go the same MPH at 100 rpm less.

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Sunday, September 6th, 2009 AT 2:00 PM
Tiny
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Hello -

I am going to request the assistance of another moderator on this. Please stand by until they contact you.

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Tuesday, September 8th, 2009 AT 9:44 PM
Tiny
RASMATAZ
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Eng analizer say mixture is to rich. Mech reset fuel air mix, My question is how did he do this-adjust for minimun air or whatever?

Running rich could be caused by the following:

Possible causes include a bad O2 sensor, excessive fuel pressure (bad fuel pressure regulator or plugged return line), leaky fuel injectors, dirty air filter or restricted air inlet, or a defective coolant sensor that prevents the engine management system from going into closed loop mode.

Please be advised that other areas will caused reduced mileage/excessive fuel comsumption instead of the engine management system. Read below

The most Common Fuel Wasters:

A Loose or missing gas caps. 17 percent of U.S. Vehicles have a loose or missing gas cap. This allows an estimated 147,000,000 gallons of gas per year to evaporate into thin air.

Underinflated tires

Faulty thermostats

Worn spark plugs

Malfunctioning engine controls

Poor wheel alignment

Fuel Saving Tip #1: Low Tires Waste Gas
Underinflated tires and incorrect wheel alignment can lead to conditions which increase rolling resistance. This is like driving with the parking brake not fully released, it can cost a mile or two per gallon on a car that normally delivers 20 miles per gallon. Correct tire inflation pressure is critical for good fuel economy, safety, maximum tire life and proper vehicle handling performance.

Fuel Saving Tip #2:Keep your car in tune:
Keeping up with regular vehicle maintenance can improve gas mileage by an average of 4.1 percent. Results may vary depending on the kind of repair and how well it is performed. Ignition misfires are one of the biggest fuel waters of all!

Fuel Saving Tip #3: Keep Your Air Filter Clean
An air filter clogged with dirt, dust and bugs chokes off the air and creates what is called a "rich" mixture - too much gas being burned for the amount of air, which both wastes gas and causes the engine to lose power. Replacing a clogged air filter can improve gas mileage by as much as 10 percent.

Fuel Saving Tip #4: Change Your Spark Plugs
A vehicle can have either four, six or eight spark plugs, which fire as many as 3 million times every l, 000 miles, resulting in a lot of heat, electrical and chemical erosion. A dirty spark plug causes misfiring and that wastes fuel. They need to be replaced regularly.

Fuel Saving Tip #5: Improve Your Driving Habits to Improve Fuel Efficiency:

Avoid quick or 'jackrabbit" starts and stops.

Aggressive driving wastes gas. It can lower your gas mileage by 33 percent on the highway and 5 percent in the city.

Observe the speed limit. Gas mileage decreases rapidly above 60 miles per hour.

Avoid excessive idling. Idling gets 0 miles per gallon. Turn your engine off if you are going to be stopped in traffic for 15 seconds or longer.

Use cruise control because it helps you maintain a constant speed limit.

Use overdrive gears because the engine speed goes down saving gas and reducing engine wear.

Avoid carrying unneeded heavy items in your trunk. An extra 100 pounds in the trunk reduces a typical car's fuel economy by 1-2 percent.

Use air vents to circulate air instead of air conditioning.

Fuel Saving Tip #6: Practice Preventive Maintenance:
Simple preventative maintenance steps that you can do to conserve energy, protect your investment, improve highway safety and benefit the environment include:

Regularly changing your motor oil. Dirty oil can reduce fuel economy up to 1 mile per gallon! To maximize fuel economy, use a 5W-20 or 5W-30 synthetic motor oil.

Keeping your tires properly inflated (32 to 34 psi is about right for most cars)

Taking your vehicle for annual brake inspections (Dragging brakes can waster fuel).

Get your transmission fixed. A slipping automatic transmission can cost you 1 mile per gallon or more. It's the same story if you have a manual transmission with a slipping clutch.

A bad cooling system thermostat that causes your engine to run too cold can reduce fuel economy up to two miles per gallon.

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Tuesday, September 8th, 2009 AT 10:20 PM
Tiny
DON22
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Your answer gave me no idea what to do next, except to check fuel return line. I keep this van in top shape. Regular maintence, tires are filled with nitrogen at recommended pressure. Please read all my replies to see what I have done to figure this problem out. Don22

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Wednesday, September 9th, 2009 AT 9:30 AM
Tiny
RASMATAZ
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Be advised we've given you every possible means and ways that can cause your problem fixing a vehicle over the internet is a lot tougher than actually being with it-This is not a simple fix it can be very costly to figure it out and drag on

Do a fuel pressure check with a fuel pressure gauge and report back with the readings. BTW when was the last tune-up check the plugs condition its due 100K miles-If you're not satisfied with our answers I suggest you request for refund but be advised services been rendered.

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Wednesday, September 9th, 2009 AT 12:03 PM

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