Worse MPG after cleaning MAF?

[ArmArak]

Hi guys,

I was getting pretty bad mileage (13.5 mpg), so I decided to clean my MAF sensor. It was very dirty! Immediately after cleaning I noticed smoother acceleration and a lower RPM for any speed. Previously I would cruise 40 mph at 2k rpm, now, after cleaning, I cruise 40 mph at 1.6-1.7k rpm. The issue is I am somehow getting worse mileage (12 mpg). I just filled up 17.5 gallons yesterday and I had only driven 199.0 miles. Considering I am on 33s that's actually around 216 miles.

What I have noticed is that on startup, there is a stronger somewhat sweet smelling gas smell than before. Will it take a few tanks for the clean MAF to start taking effect? What could be causing the stronger smell? I am going to
replace my 02 sensor soon, could that be the issue?

Thanks!

 

[phattyduck]

Maybe you are just smelling it differently due to the recent weather change?

I'd suggest that 200 miles isn't exactly enough to gauge mileage.

There should be no difference in cruising RPMs between dirty and clean MAF - something else is going on there. Probably just slightly different driving conditions.

-Charlie

 

[Malcolm99]

Firstly, your RPM's remain consistent according to the speed you're going and what gear you're in, at 40mph your RPM's are what they are unless you changed gears or changed gear ratios or tire size or have a slipping tranny or clutch where applicable. 33" tires are big for 4.30 ratio gearing, I have 32.5" tires with 4.30 ratio and it hurt my mileage and performance. I assume you have a v6 4.10 ratio Automatic with no elocker, yes the Front O2 and MAF contribute a lot to good mileage, but my other truck with 33x12.5" and 4.30 ratio also suffered from poor mileage, and winter fuel doesn't help either, try premium if you can afford it for a few tanks with injector cleaner. It's your tires that is robbing you of mileage.

 

[3bears]

check your hose fittings and clamps.

maybe your computer needs to relearn things....after some repairs its a needed step. Whenever I clean the maf or throttle body, I reset computer. Some people say you should reset with change of ownership so computer "learns" your driving style. Who knows ?

Anyway

Several ways to do it, but I just disconnect my negative cable for about an hour, then hook it back up ( instructions say only half hour needed). Of course with this way you will have lost your radio presets. That does not bug me to reset them, I know it bugs others, but I only have a few .
There is also a method where you pull a relay...someone else can chime in on that method and you dont disconnect battery or loose your radio presets.

 

[ArmArak]

Maybe you are just smelling it differently due to the recent weather change?

I'd suggest that 200 miles isn't exactly enough to gauge mileage.

There should be no difference in cruising RPMs between dirty and clean MAF - something else is going on there. Probably just slightly different driving conditions.

-Charlie

Firstly, your RPM's remain consistent according to the speed you're going and what gear you're in, at 40mph your RPM's are what they are unless you changed gears or changed gear ratios or tire size or have a slipping tranny or clutch where applicable. 33" tires are big for 4.30 ratio gearing, I have 32.5" tires with 4.30 ratio and it hurt my mileage and performance. I assume you have a v6 4.10 ratio Automatic with no elocker, yes the Front O2 and MAF contribute a lot to good mileage, but my other truck with 33x12.5" and 4.30 ratio also suffered from poor mileage, and winter fuel doesn't help either, try premium if you can afford it for a few tanks with injector cleaner. It's your tires that is robbing you of mileage.

Thanks for the response guys. I went through that 200 miles over the course of the last month and a half (Yes, I don't drive much haha) so for sure the smell is not the weather related. I'll keep tracking how the mileage goes as I continue driving because I agree that 200 miles isn't really enough.

The reason I think I noticed the rpm change is because I think I might be making more power throughout the rpm range in total, so at 1.7k rpm I am making the power I used to make at 2k. Do you think it's possible? I be no means am an expert on this haha, but I for sure noticed that change immediately after the MAF cleaning.

As for tires I am running 255/85/r16 Toyo mud tires which are 33.5 inch tires and I am still on stock gearing (2001 v6 auto no e-locker). When I regear will I get better mileage?

Ill try the fuel injector cleaner with some premium fuel next month when I have to fill up again lol.

 

[Malcolm99]

Yes, you can experince a better air fuel mixture for any given RPM's by cleaning the MAF making it feel more responsive and operate more efficiently, resetting the ECU might speed up the relearn process for optimal fuel trims, you being on 33.5" Mud terrains(often heavy as are aftermarket rims) and lifted 3-4" changing drive shaft geometry and wind resistance will rob you of mileage big time, add the fact you have 4.10 ratio gearing will make it worse so it will be kicking down more often on any incline. The smell I notice whenever the front O2 goes is the rotten egg smell with rear window down.

 

[Bad Luck]

The reason I think I noticed the rpm change is because I think I might be making more power throughout the rpm range in total, so at 1.7k rpm I am making the power I used to make at 2k. Do you think it's possible? I be no means am an expert on this haha, but I for sure noticed that change immediately after the MAF cleaning.

It's more likely that you have either gone gone from 3rd to 4th or the torque converter has locked up in 4th gear. Are you driving with ECT power on or overdrive turned off?

 

[ArmArak]

It's more likely that you have either gone gone from 3rd to 4th or the torque converter has locked up in 4th gear. Are you driving with ECT power on or overdrive turned off?

I always drive with ECT off and overdrive on. What do you mean by the torque converter has locked up?


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[Bad Luck]

I always drive with ECT off and overdrive on. What do you mean by the torque converter has locked up?


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Automatic transmissions have a torque converter. All torque converters will slip (or allow for different engine and transmission input rpm's) until the torque converter clutch is applied. Most people mistake the torque converter locking up (torque converter clutch applying) for another shift or gear. In our transmissions (a340) torque converter lockup will occur in 4th gear with overdrive on or 3rd gear with overdrive off. With ECT off and overdrive on my torque converter will lock up around 42-46 mph depending on how much throttle I am applying.

You might benefit from driving with ECT on. Some people with larger tires and stock gearing report fuel economy gains. I on the other hand averaged 1 mpg less with the ECT on, but I have 4.30 gears and 265/70R17 tires.

 

[phattyduck]

Short trips *really* kill mileage too.

I have been getting 18-20mpg on my 17 mile, all highway, zero traffic commute... but if my wife drives is on her 3 mile, all side-street commute it would be the numbers you are seeing.

-Charlie

 

[ArmArak]

Short trips *really* kill mileage too.

I have been getting 18-20mpg on my 17 mile, all highway, zero traffic commute... but if my wife drives is on her 3 mile, all side-street commute it would be the numbers you are seeing.

-Charlie

That’s interesting. I also have a short commute. Twice a week I drive it 7 miles to my internship, all street and heavy stop and go traffic. For the past few months the car has seen basically zero highway miles. I guess I can’t expect too much haha. The smell on startup is the only thing that’s concerning I guess. I’ll change my 02 sensor next weekend and see if I not any improvement or if the smell goes away.


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[3bears]

with those kind of driving conditions and the way your truck is equipped....these trucks SUCK fuel. Also in those conditions the truck is getting no place near running temps and I would not mess with O2 sensors or anything. Take it out on the hiway and BLOW IT OUT, heat it up, get back on the back roads and trails you have talked about in other threads

my experience anyway

 

[Thebeastlives]

I added this recently to the Truck and mpg increased and the truck had a little more power. It cleared the smell on acceleration as well. The stuff ain't cheap but it does work.