[Ray!]

Over the Australia Day weekend, we did a five day cruise, where I found the fuel economy of my CRD turning crapola, way higher than before, even when doing a lot of low range driving. The Patrol in all other respects ran fine and showed no signs of having any issues, but on the third day the fuel gauge was dropping like a stone. I couldn't find anything wrong and on the fourth day after filling right up the night before, I decided to check the MAF.

The first thing I noticed was that the air cleaner was the wrong way up, the rubber double lip was at the top (obviously the cleaner was checked at the 60K service, but was put back incorrectly - something I'll point out to the service department). Other than the guts of the MAF being covered in a layer of dust, there was no oil residue or anything else nasty looking within; that said, I used some contact cleaner and gave the unit a good clean to get rid of the dust layer. Back at Moe on our way home, I filled up fully and for the next two fills, monitored the fuel consumption.

Well, I have to say that the clean must have had a real impact. Despite the fact that one part of the trip saw me getting woeful fuel economy, the average for the trip actually came out at around 15lt/100km (around 1400km travelled before final refill). My fuel consumption has hovered around 13.5lt/100km for some time now (just city/highway driving), but after three fills since the MAF clean, I'm now getting about 12.2lt/100km. If that keeps up, I'll be very happy, as that translates to about 11lt/100km if it were a manual transmission.

Interestingly enough, many say that they find their MAF covered in oil residue, yet mine was completely dry, other than for the dust. But given this experience, I'm going to do more regular checks of the MAF, to see if dust gets in with the air filter correctly fitted and what effect regular cleaning has on fuel economy.

The other thing that I think that this shows is that the CRD ECU does work differently and can control even issues with the MAF, where the Di would at times struggle. I think that this bodes very well indeed for the CRD overall.

Cheers

Ray

 

[Grogey]

Hi Ray,

Did you reset the ECU after cleaning the MAF? I found improvement after MAF cleaning and even more after resetting the ECU.

Is the dust you found likely to have been sucked out of the back to front air filter and if so do you think it is an issue having this dust going through your engine.

How do you think The CRD is working differently compared to the Di.?

Cheers,

Grogey

 

[Smokey2.8]

Great news, advise to clean even if it looks 'ok'.
Even notable for the RD28i owners.

 

[Rip'n'Shred]

I'd be careful using contact cleaner. You can buy proper MAF sensor cleaner spray, a bit dearer but more reassurance, not so harsh.

 

[peterowensbabs]

@Grogey how do you reset the MAF?

 

[Rip'n'Shred]

Most vehicles are a certain minimum time of battery disconnected, 1/2 hr should do it

 

[Ray!]

Hi Ray,

Did you reset the ECU after cleaning the MAF? I found improvement after MAF cleaning and even more after resetting the ECU.

Is the dust you found likely to have been sucked out of the back to front air filter and if so do you think it is an issue having this dust going through your engine.

How do you think The CRD is working differently compared to the Di.?

Cheers,

Grogey

I just disconnected and cleaned the MAF. I don't like disconnecting the ECU too much, as it takes about four days to re-learn my driving style. I don't know exactly where the dust came from, but it could have been stuff dislodged over time as the air cleaner is checked. It was not a great amount of dust, just a very fine film. I don't think it would have had any effect on engine wear.

One thing that I've never had with the CRD is overboost, so this aspect is clearly controlled differently with the CRD ECU. Also, with the Dis, when the MAF gets dirty, you usually get power loss at some point, as the ECU goes into limp mode. Now I don't know if the dust on my MAF would have been enough to cause this in a Di, but the increase in fuel usage was something I've never experienced before. So my assumption was that the ECU was just managing the dirty MAF as best as it could, but not going into limp mode.

There must be some other design aspects as well, as the MAF had no oil residue on it at all, which is usually not the case with the Di. But this shouldn't have anything to do with the ECU, I would think.

Cheers

Ray

 

[paul.helm]

I found in the past that when the air cleaner was installed upside down (rubber up), there was dust on my MAF & the EGTs were higher than normal.

After cleaning the MAF & installing the filter the correct was, the EGT's dropped but the perfofmance was crap so I changed the filter & everything was back to normal.

 

[Grogey]

Cheers for that Ray.

As it happened i did not bother with an ECU reset when i cleaned the MAF so I was impressed by the improvement created by doing that in isolation to other changes.

However, recently i left the vehicle with accessories on and got distracted for long enough with a reasonable electrical load to flatten the battery. I disconnected the battery overnight to recharge it with my CTEK.

I was very impressed in the following days and would say the motor is now running better now than at anytime before in the 20,000km i've owned it.

Grogey

 

[Ray!]

That's interesting, as I usually find less get up and go, until the ECU learns once again.

On another issue, I bought a new air filter today and when installing it, found the lid to be quite tight to latch up. So I took the new filter out and compared it to the old one. Lo and behold, the rubber ring (not the one with the dual lip) was nearly twice as thick on the new filter compared to the old one. I wonder if Nissan has discovered that the ring wasn't sufficiently thick enough and was prone to letting in dust?

Cheers

Ray

 

[MAVREX]

Great info Ray, thanks for posting.
My fuel economy has dropped (~50k) since using a K&N around town, but MAF hasn't been cleaned in a while either, might be time considering what dust did to yours, even though mine is Di. Possibly go back to factory nissan air filter as i have noticed nil difference with K&N and could be letting crap in over the top seal.

Thanks.
MAVREX

 

[LittleJohn]

Ray, makes total sense.
Im a truck driver owner, and have been for some 17+ years,
the most economical setup on our trucks are those with the snorkels tucked behind the cab or facing sideways just behind the cab.

We did try with extentions over the cab and over the wind deflerctors, to see if the extra air would
increase economy.. ie more air in the chamber theory etc.

but we did find a drastic difference in a positive way , by just leaving the snorkels,
out of the way , away from the fast turbulant air.
more fuel/more air/ more horsepower/ which was awsome, but
when working for every cent you can muster, it wasn't such a great idea.

I do wish i could spin my snorkel around on my GU now come to think of it,
but its the new factory curvy one, and its shape prevents me fro spinning it backwards.

ps. with the trucks, we are considerring gas injection now, still awaiting anual figures to come through from companies who are trialing it still, both local, and long haul.

 

[Ray!]

John

That's an interesting point. For those that may remember the original Nissan GQ factory snorkle, it flowed in one continuous motion to the roof and finished up above the door, with the inlet facing the roof. This sort of describes what you illustrated. I'll bet Nissan tested the snorkles in a wind tunnel or did CFD analysis to determine the best design and location of the snorkle. Nowadays all snorkles are much the same with the front facing scoop, designed probably with the misguided belief that one gets a ram effect, which simply won't happen.

Cheers

Ray

 

[LittleJohn]

One other thing Ray,
our trucks have dual air filters, one outer, and one inner inside it.
This method is extremely constrictive, for diesels needing freed up horsepower.
the engines just suffocate, litterally...
so what we do is we get rid of the inner filter, and the engines run to their absolute optimum,
( if only i could show you the difference, you'd be amazed),
we use genuine filters, or fleetguard if theys not available., but only till we can get a hold of genuine ones.

So i do believe, if we use Nissan genuine air filters,( aftermarket ones are way way tighter and more constrictive) and do turn our snorkels side on or backward,
your fuel consumption figures will amaze you, that extra litre per 100 is a huge variance when on the highway, or runnin round town.
We may not all be driving to make a dollar like myself , but it all costs us to travell " anually" regardless. we all have bills,bigboys toys, families to feed etc etc , every bit saved counts in the longrun.

 

[Frosty]

Headed to Dick Smith's today and purchased a can of Electronic Cleaning solvent to clean the MAF after reading

this thread and a few others.
Pulled out the MAF under surgical conditions

and to my amazment, thought it look relatively clean. But then sprayed the cleaner on the sensor and wow, the crap that came off, it was unbelieveable

. Mind you the 4bee is a 2002 Gu with 177K. I used a cotton bud to clean the left over residue and it was like looking in a mirror. Heading to the Springs tomorrow, so time & miles will tell how things went. Will let you know.

 

[skamme]

cleaning maf

AT 120k now, the urge to clean my maf has struck. To my surprise, the local super cheap has crc mass air flow sensor cleaner in stock! Cleaned up, now to see if there is any difference. price was $25...
CRC Mass Air Flow Sensor Cleaner - 300G - Supercheap Auto Australia

 

[cabhsv]

I did a maf clean on my CRD the other day first time and have notice that my boost is very responsive now and hits over 16/17psi very easy, and I have noticed it jumps around a little more than before, is this normal after the clean?

 

[mainey88]

I did a maf clean on my CRD the other day first time and have notice that my boost is very responsive now and hits over 16/17psi very easy, and I have noticed it jumps around a little more than before, is this normal after the clean?

Mine does the same but now that I have a 3" exhaust the boost can easily spike up to 22lbs but drops off quickly.

 

[NZUrvan]

One other thing Ray,
our trucks have dual air filters, one outer, and one inner inside it.
This method is extremely constrictive, for diesels needing freed up horsepower.
the engines just suffocate, litterally...

Removing the inner, where genuine inner and outer are fitted, provided slightly faster access to peak revs, where we don't want drivers and operators to go. May be more torque at higher revs, but we want long life and low maintenance costs, so didn't test.

Owner operators with deep pockets and / or vehicles not under warranty or on maintenance plan could give it a try.

 

[davess]

I cleaned the MAF sensor on my 4.5 on the weekend and holycow! It had been a slug on petrol, not wanting to accelerate at all to the point where I was thinking fuel pump or injectors but now it's driving normally.