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Mass Airflow Sensor going bad??

Old 07-04-2011, 06:07 PM
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tracyballard
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Default Mass Airflow Sensor going bad??

I have been working on a Service Engine Soon light for a while now. the first time it came on I had Autozone check the codes and I got 0171, 0174, 1130 & 1150. I changed the spark plugs, cleaned the MAF with MAF cleaner and the throttle body with TB cleaner, and also replaced a hose that had a 2 inch long crack in it - the short hose that comes off the PVC valve on the passenger valve cover. I also cleaned and re-oiled my K&N air filter.

NOW - the Service Engine Light Soon light went out for a few days after I did that, but now it's back on (maybe 20 miles with it staying off, and running much better with more power and revving much more easily). I checked to make sure none of my spark plugs had backed out, no problem there, and had Autozone run the codes again - now it's only the 0171 and 0174 codes showing up, which means it's running lean on both banks. So....does that mean the MAF is the problem??
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Old 07-04-2011, 09:24 PM
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cliffyk
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Since it is both banks it is obviously something common the both banks, as is the MAF. Examine it ind see if it has been fouled with dust/grime; K&N filters are known to do this--it's not common with new ones, but it happens--it is more common with cleaned and over-oiled filters.

All you have to do is look at it, the thermistor and heater look quite a bit alike and they should be clean with little to no film or dust accumulation. With the exception of physical damage to the thermistor/heater, and possible damage to the electronics from overloading, etc., there is very little to go wrong with a MAF.

In the absence of fouling they generally either work or they don't.

Here is what the shop manual says about P0171 (P0174 is the same, just bank 2)--work the list from the top down...
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Old 07-06-2011, 09:33 AM
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I cleaned the MAF again with MAF cleaner, cleaned the whole air filter enclosure with brake cleaner and put the K&N air filter in it's proper place - the box that my new Motorcraft air filter came in. That didn't fix the problem, so now I've ordered a Fuel pressure tester to check the fuel pressure before I think about getting a new MAF. it will be a few days before I get the tester, so in the meantime any suggestions are welcome. thanks in advance!!
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Old 07-07-2011, 08:22 AM
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cliffyk
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Are you able to data log either the MAF airflow or MAF voltage PIDs? Their values at various RPMs while at steady throttle would let you know if the MAF is functioning properly.

Also, and you have likely done this already, make 110% certain there are no air leaks in the intake tract after the MAF.

Have you tried disconnecting the battery for 5-7 minutes to force the PCM to relearn the air, and short and long term fuel, trims?
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Old 07-07-2011, 10:23 PM
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Originally Posted by cliffyk View Post
Are you able to data log either the MAF airflow or MAF voltage PIDs? Their values at various RPMs while at steady throttle would let you know if the MAF is functioning properly.
I have no idea how to do that - does this involve having a device to plug into the access port under the dash on the driver's side like when autozone reads the trouble codes?
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