Gas mileage question

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Bigmd

New member
Ok lately been noticing my mileage sucks . I haven't figured out what exact numbers are but it seems on par with my 08 Mustang GT I sold before my runner. I have installed slightly bigger tires 265/75 so i thought that may be a factor. I recently replaced fuel filter and did plugs and wires with seemingly no change. Today I get a CEL along with the vsc lights. I trip to autozone revealed via their scan tool a C1201 and P0171 codes. I googled them and seems a MAF cleaning is what most suggest to do first. I pulled it and sure enough one side is black. Cleaned it and put it back in. The code was cleared at autozone and so far hasn't reappeared. Could this be affecting my gas mileage? If it reappears should I replace the MAF sensor? The C1201 I'm still trying to figure out. Also I replaced the pcv valve and grommet weeks ago. The hose was hard and dry and did notice oil on it today ,so I assumed it was probably leaking. Replaced with new hose. I'm thinking it was part of the problem. Thanks in advance
 
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One more thing to add is the truck has 156000 miles on it and as far as I know the O2 sensors are original.
 
Winter blend fuel hits me hard. Theres additives to keep it from freezing so gas mileage in the winter always sucks.
 
The MAF most definitely will affect your gas mileage. Another factor is if you are finding old cracked hoses you may have a vacuum leak. I'd replace any other hose that looks cracked or worn. You can check for leaks elsewhere by using this technique:

https://www.youtube.com/watch?v=9CPqbaSgcok

Your front O2 sensor might be on its way out. Over time they work less effectively until it throws a check engine light. Then again, replacing it might not do anything.

New spark plugs if worn, plug wires, and running injector cleaners through the gas can also help regain lost MPG's.
 
Thanks for responses . Plugs and wires were done a few months ago. Injector cleaner also. Also replaced the one hose today I'll check for more. So far so good. I'll hold off on sensor until the lights come on again.
 
P0171 is a fuel trim lean code, meaning the computer will be compensating by making the mixture RICHER, this can be a false code if the computer cannot monitor airflow. You could have a vac leak, exhaust leak before the O2 sensor or the maf could be dirty as you found. The computer this the code because it detects too much Oxygen in the exhaust (it doesent check for fuel for those wondering, but determines rich/lean by the presence of O2) so I would not start by throwing o2s at it. Just wait and see what happens after you cleaned the maf.

Is there any other running issues?
 
No issues . Runs fine idles fine. No hesitation. Decent acceleration. Wasn't going to do sensors yet. Next step I would think would be new MAF if it continues . The Maf sensor was all gunked up. I put a filter in a while ago from Burtma Industries. So I'm thinking some of that oil got to it.
 
C1201 is engine control malfunction right? If it is this is normal on vehicles with VSC when the check engine light is on. Basically its just saying that the two arent working together until the problem is fixed.
 
another possibility is IF you have an air filter that requires OIL and if you over oil it that could turn the MAF black.
 
Bigmd said:
Ok lately been noticing my mileage sucks . I haven't figured out what exact numbers are but it seems on par with my 08 Mustang GT I sold before my runner. I have installed slightly bigger tires 265/75 so i thought that may be a factor. I recently replaced fuel filter and did plugs and wires with seemingly no change. Today I get a CEL along with the vsc lights. I trip to autozone revealed via their scan tool a C1201 and P0171 codes. I googled them and seems a MAF cleaning is what most suggest to do first. I pulled it and sure enough one side is black. Cleaned it and put it back in. The code was cleared at autozone and so far hasn't reappeared. Could this be affecting my gas mileage? If it reappears should I replace the MAF sensor? The C1201 I'm still trying to figure out. Also I replaced the pcv valve and grommet weeks ago. The hose was hard and dry and did notice oil on it today ,so I assumed it was probably leaking. Replaced with new hose. I'm thinking it was part of the problem. Thanks in advance
Click to expand...

MAF could definitely be part of the problem. What gears are you running? did you regear when you went to 265/75? I'm about to go to that size myself, and am going to 4.30 (installing elocker, figured why not) One thing that helped me with mileage a lot when I bought my 4runner was replace the spark plugs and clean the MAF. Surprised replacing plugs didn't work for you, hopefully the MAF helps, especially if you said it was black when you checked.
 
Ok throwing 8 codes but 3 of them were the p0171 (pending, completed,and history ) also the c1201 again. The new ones are c1223 antilock malfunction.
C1246 mc pressure sensor. P0420 catalyst system below threshold . I have been noticing the abs lights would come on once in a while while normal driving.then would go off quickly or after I restarted the car. I have done the 1st generation Andy mod. Not sure if that's doing that. I'm running stock 410 gears. Also running the burtman industries oiled filter. That's been on for months.
 
Cleared codes this afternoon and they are back already. Looks like it could be the maf sensor or O2 sensor. Think I'm ditching the filter for a paper filter too. I googled the abs code and it seems that could pricey. Any suggestions?
 
Bigmd said:
Cleared codes this afternoon and they are back already. Looks like it could be the maf sensor or O2 sensor. Think I'm ditching the filter for a paper filter too. I googled the abs code and it seems that could pricey. Any suggestions?
Click to expand...

No advice on the ABS codes other than they are usually paired together. C1223 is just something wrong with the ABS, the other is more specific, fix it and the other should go away. P0420 from what I understand can sometimes be fixed by replacing O2 sensors but usually has to do with Catalytic Converter. I myself threw a P0107 fairly often when I had my old Volant intake on my 4Runner, got rid of it and replaced with a LIGHTLY oiled K&N filter and AirAid intake and haven't had it since. I plan on switching to a good dry filter but seeing as I don't plan on taking it off road until my build is done, I haven't gotten around to it.
 
Bigmd said:
Battle wagon it's an oiled filter from Burtman. When I cleaned MAF it was coated in oil.
Click to expand...

I would clean the MAF again, then replace that filter with a good dry one.

I have the Airaid Jr kit with the Synthamax dry filter and it is very nice, good air flow and nothing gets past it.
 
Thanks guys , definitely going with a dry filter. Most likely will also go ahead and do the o2 sensor and MAF since they are both inexpensive. The abs code on the other hand is not a cheap fix. The limited info I read is you pretty much have to change out the whole brake booster . They go for over a 1000 bucks new. Although I found them used for under 400 on eBay. I also read of peoples brakes freezing up with this code.
 
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