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OK, due to a dropoff in mileage over the last two months or so, I've obtained a product to clean my MAF sensor. I also removed the throttle body and thoroughly cleaned it. All electrical components were removed before I dumped it in a bucket of gas.

This cleaning resulted in a slight increase in mileage-about 1 MPG. The state of tune is fine-the plugs, pcv, and air filter are all new or close to it.

So the question is, does the MAF sensor on my car need replacing? I've got about 174K on it and it came with the car. Does it affect mileage much? I went down about 3 MPG with no change in driving habits.

I'm reluctant to just replace it because of the cost. The local parts puppies run about $139, although a Python (?) brand goes for $91.

Thanks in advance for your advice.

Bob.

(ETA: no CEL and no codes)

I would just keep running with the current MAF sensor. There are a bunch of sensors on these cars that you could just go ahead and change - but probably for no good reason. Unless you just like to spend money. It seems to me that the final air/fuel ratio is determined more by what the O2 sensor reads. Your mileage could be affected by how much ethanol is being put into the gasoline.

Unless the sensor is malfunctioning far out of range, which would call attention to itself very quickly with a SES light, they tend to be black and white, working or not. A MAF sensor can very severely affect your mileage, but only when malfunctioning. Bad mileage leans more towards a post combustion sensor like the oxygen sensor. Every 80-100k for heated oxygen sensors is the recommended replacement interval...is yours in that interval currently?

wjcollier07 wrote:Unless the sensor is malfunctioning far out of range, which would call attention to itself very quickly with a SES light, they tend to be black and white, working or not. A MAF sensor can very severely affect your mileage, but only when malfunctioning. Bad mileage leans more towards a post combustion sensor like the oxygen sensor. Every 80-100k for heated oxygen sensors is the recommended replacement interval...is yours in that interval currently?

02 sensor is new within about 40K, and it's genuine GM. This is puzzling; compression checks out, too, and plugs look fine. I suppose, as above, it could be the amount of alcohol in this gas.

wjcollier07 wrote:Unless the sensor is malfunctioning far out of range, which would call attention to itself very quickly with a SES light, they tend to be black and white, working or not. A MAF sensor can very severely affect your mileage, but only when malfunctioning. Bad mileage leans more towards a post combustion sensor like the oxygen sensor. Every 80-100k for heated oxygen sensors is the recommended replacement interval...is yours in that interval currently?

thats not entirely true, they can be off enough to effect performance and economy, but not far off out of spec for the pcm to set a DTC.


what kind of mileage are you getting?

Wes wrote:
what kind of mileage are you getting?

About 18 overall. From the time the car was new and until recently, it got about 21 overall.

Yes, Wes, that is very true, its that very reason we keep them clean. The build up on the filament causes that small inaccurate reading to occur, decreasing efficiency.

Dillon, I assume you have a scantool? It would be good to watch the live data to see if something is out of range. A/F ratio, MAF flow readings abnormally fluctuating, Oxygen sensor not switching fast enough, etc.

Has your area recently introduced ethanol or maybe using it more widely than before? I've noticed pretty large changes in mileage from station to station...do you always use the same station?

wjcollier07 wrote:Yes, Wes, that is very true, its that very reason we keep them clean. The build up on the filament causes that small inaccurate reading to occur, decreasing efficiency.

Dillon, I assume you have a scantool? It would be good to watch the live data to see if something is out of range. A/F ratio, MAF flow readings abnormally fluctuating, Oxygen sensor not switching fast enough, etc.

Has your area recently introduced ethanol or maybe using it more widely than before? I've noticed pretty large changes in mileage from station to station...do you always use the same station?

No scantool, just a code reader. I'll ask around. I have switched gas stations recently. Hmmmm.

But all CA gas is crap anyway. Whenever I go to Nevada, I fill up and get about 15% better mileage on the way home.

92; bonneville se, 3.8 mpfi. no blower
engine diffcult to start and blogs and backfires when throttled. I diconnected maf and runs alot better.
I have sprayed carb cleaner in port and probe on maf with no improvement, i have also replaced maf with used one with no change. Could the problem be with the o2 sensor or another sensor? Or maybe I
didn't clean it properly? I ckecked ecm codes after my post procedures, still have code 34.

Please start a new thread.

Bob Dillon wrote:OK, due to a dropoff in mileage over the last two months or so, I've obtained a product to clean my MAF sensor. I also removed the throttle body and thoroughly cleaned it. All electrical components were removed before I dumped it in a bucket of gas.

This cleaning resulted in a slight increase in mileage-about 1 MPG. The state of tune is fine-the plugs, pcv, and air filter are all new or close to it.

So the question is, does the MAF sensor on my car need replacing? I've got about 174K on it and it came with the car. Does it affect mileage much? I went down about 3 MPG with no change in driving habits.

I'm reluctant to just replace it because of the cost. The local parts puppies run about $139, although a Python (?) brand goes for $91.

Thanks in advance for your advice.

Bob.

(ETA: no CEL and no codes)

After doing 110mph on I78 going from NJ to PA im sure it was my fault but....
I Honestly would just go ahead and replace it, I just went through a rough patch with not only my Mass Air flow sensor but my camshaft sensor as well i had them both replaced(she wasn't starting before i had them replaced) and notice a huge difference from where i was beforehand sensors are definitely expensive i spent 126.00 on my maf from Auto zone replaced it myself but my friend and i replaced the camshaft sensor together and i put in a K&N Reusable air filter i spent about 350 or so. If its not causing problems it's up to you.

Bob, if you can do get a Tool on that car and see if the MAP, MAF and O2 are within range... Even tho the O2 was new thats not to say it can't be having issues as well...

On a side note, it doesn't get as cold here, but the 03 is doing 22 Mpg City, The 95 Bonneville with the 97 harness and PCM is doing 26 average and thats mostly city..

The van with its cam is doing roughly 18-20...

all of this on 87 fuel with 10% Ethanol... A good scan could lead you in a better direction..

How the heck did I miss that??

Time to throw the Master at this....