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Can cleaning a mass air flow on Ford Taurus 2005 decrease mileage?

I had a check engine light on my 2005 Ford Taurus and my mechanic suggested cleaning the mass air flow. Afterwards, the light was off and the car seemed to drive fine ( it was driving fine even with the check engine light on) But my mileage dropped drastically. On the freeway it went all the way down to 10mpg! Right now around town it is fluctuating a bit, but around 14mpg. Should I have the mechanic check for a loose wire or something not connected properly? Or just replace the darn mass air flow?

I would suggest that you get a new mechanic.
But, first, you should check to see if there are still any trouble codes remaining in the OBD system’s memory. An auto parts retailer (Auto Zone, Pep Boys, Advance Auto, O’Reilly, possibly Napa) will do this, gratis, in the hope that you will buy parts from them.

If there are any trouble codes, please post them in this thread for specific advice.
However, at this point, I DO think that you need a new mechanic, as there is undoubtedly much more to this issue that is apparent right now. For instance…what can you tell us about the car’s maintenance over the past 3 years? If your mechanic is approaching this problem without first bringing the car up to date on maintenance, it could take a very long time before he resolves the problem.

You don’t want to just replace the MAF sensor.They’re not cheap. Instead have your mechanic go for a ride with you with a scanner plugged into the vehicle while monitoring throttle position and Mass Air Flow. Then at some point put accelerator the floor. The scanner will reflect 100% throttle position while at the same time reflect the grams/sec of mass air flow. Then look up the spec for grams/sec @100% throttle position for your vehicle.


thank you both for your timely input. I will take the car to pep boys and get the obd checked. I’ll post again when I have that info. Again, thanks a lot for your help.

MAF refefs to the “mass airflow sensor” . This is the gadget that measures how much air is being fed into the engine. The engine computer then decides how much gasoline is necessary to burn w/ this amount of air. If the MAF is providing inaccurate measurements of air flow, it indeed could cause the computer to inject too much (or too little) fuel.

I’ve never heard of the need to clean a MAF myself, but I’ve nevered worked on fuel injected Fords either. Cleaning the throttle body is common, but I guess I can imagine that sometimes the MAF needs to be cleaned too. Replacing it I imagine is expensive, so try to avoid doing that if possible.

Also suggest to re-check the mpg. 10 mpg on the freeway is far off enough from normal that I’d expect the car to be misbehaving, surging at idle, etc., gasoline smell from the exhaust, and generally not acting normal when driving around town. Since you don’t report any other problem, it is possible you made a mistake in measuring in the freeway mpg. Double check that first.

Is it possible the MAF was cleaned incorrectly? IE, was it cleaned with a solvent that was too strong or did the wire get damaged during the cleaning?

The miles per gallon indicated on the dash is not an actual measurement of gallons/miles. The indicated mpg is just an inferred value. And although the car might actually be using that much fuel it is more likely that an input used to calculate the performance is not operating correctly. And, yes, when the MAF was cleaned it might have been damaged or a connector might not have been properly made. The shop should be happy to confirm that their work was done properly. There’s a good chance that when the OBD II live data is scanned the problem will be seen fairly quickly.

I’m betting it was damaged. And as Rod suggested, I too will bet that a code scan will find a stored code suggesting a bad MAF sensor.

MAF’s do get dirty, especially if you use one of those “permanent” washable, oiled air filters. But even with a regular paper filter, they can and do get dirty. When they get dirty, they usually start to lean out the engine, so you may get slightly better gas mileage. It won’t be much, and to detect it, you would need to keep accurate records of the amount of gas you put in at each refill and the miles driven between each refill. You have to average several refills because one refill will not accurately gauge your mileage.

When you get the check engine light for running lean, if you don’t correct the problem, you run the risk of predetonantion in the combustion chamber and higher combustion chamber temperatures that can lead to burned valves, so you need to address it. The gas mileage will drop back to normal.

But your case is not normal. Since this started right after cleaning the MAF sensor, I suspect that it got damaged and you should be getting a code for running to rich in the near future if you don’t have it already. I’m afraid that once damaged, its an expensive repair.

I would also recommend that you take Tester’s advice seriously too. You really want to know its the MAF sensor before you buy one, they ain’t cheap.

I’ve had a couple problems with MAFs. Usually, the car wouldn’t hardly run at all like a fuel starvation issue. But one simply caused the car to run rich. I’ve cleaned them but never had it correct anything. I’d be more suspect of the O2 sensors causing a rich condition. Only way to tell is to get the codes checked and get a computer on it to see if it is running rich and if so based on what.