Juandotto

Good night guys from Spain.


I´m going to remove the Mass Air Flow for cleaning with the CRC cleaner for MAF and I see that it´s so difficult to conssent at the flat screew. I´m going tomorrow to buy a new flat screewdriver more lenght.


At the moment, the Maf looks ok and not have any dirty. I think that the previous owner change the air filter when was necessary.


I´ll try to put any fhotographs of my Maf and you see....


Bye

Speedtoys

No such thing as a dirty MAF. (hotwire style)

Do not "clean" it.

They self clean.

You could create a $350 mistake.

Juandotto

Speedtoys, really not clean?????

I have read that cleaning the Maf you can win some horsepower....


My car it's ok in all the things that can be replace: timing belt, new oil and his filter, air filter, water pump, auxiliar belts, brake fluid, coolant fluid, etc.....


But I think that my car should be more poder, because in highway is a bit slow when push the throttle. The drive at low speed is ok, but at high speed it seem that above 4000 rpm doesn't work fine.


I think that cleaning the Maf it get better. But at View the estate of my Mar, without dirty, i doubt......


Thanks!!!

Speedtoys

Hotwire MAF's clean themselves when you turn the car off, they reach about 2000d for a few milliseconds.

Lots of people read lots of things. Welcome to a 928 focused forum.

You should describe your condition with more detail, over 4000 it does, what?

Mrmerlin

based on the color of the white bushing in your crank position sensor it could be time for an intake refresh .

NOTE if its not running well then sending the MAF off for a rebuild would be part of the refresh

Juandotto

Thanks Speedtoys and Mrmerlin.


This afternoon I have take some photos of the wire. I see that looks fine, and I don´t know if clean the Maf with the CRC.


Speedtoys, the car Works ok at low speed. But, for example, i drive at 60 mph in 3º gear. When I push at total trhottle the engine gets rpm very slowly, 3500 rpm, 4000 rpm, 4500 rpm very slowly. I think that my car with 320 hp must be more fast al high speed.


Have Anyone experience in cleaning the Maf ???? and, have obtained good results???


Thanks!!!!!

Speedtoys

...what is your obsession with cleaning a perfectly CLEAN maf hot wire?

They self clean..best case, nothing happens, worse..you need a $350 MAF.

is that translating ok?

dr bob

MAF cleaners are more appropriate for the thin-film sensors than for hot-wire sensors. Car manufacturers moved away from hot-wire sensors when they were forced to extend emissions warranties past 100k miles.

As Jeff (Speedtoys) described, the start cycle for the MAF includes a brief high-temperature burn-off cycle to turn any accumulated deposits on the wire to ash. The subsequent airflow as you start the engine removes the any remaining ash. Each cycle of heating can also let some of the wire itself deteriorate, as it gets red-hot then has ambient-temperature air drawn across it. Kind of like the filament in a light bulb, without the benefit of the oxygen-free argon gas blanket that the light bulb enjoys.

Your pictures of the wire tell us that there is no remaining ash or other deposits on the wire, so cleaning will provide no benefit. Further, the plastic bell above the wire can be easily damaged by solvent-based products such as the CRC MAF cleaner.

------

Depending on how the car is used, you may find that there are other related causes to your perceived power loss at higher engine loads. Virtually all show up with an engine "miss", as cylinders fail to fire due to fuel or ignition problems. If you don't have any engine "miss", there are some factors that affect the tuning.

-- Knock sensors and the cam position sensor must be functioning correctly, or the ignition controller will subtract ignition advance to protect the engine.

-- The switch on the throttle body detects when the throttle is more than about 2/3 open, signalling the fuel and ignition units that there is a higher load demand. This moves the controller to "open loop" control, during which time it will ignore the oxygen sensor in the exhaust and make adjustments for more power.

-- The intake resonance flap needs to operate correctly to generate full power. This flap cycles on initial key-on, so can be tested with a helper cycling the ignition. Watch for the black cap in the middle of the top of the engine intake manifold to rotate 90º and back. If it does that, the flap and controls are working correctly.


If the knock sensors have not been replaced already, they are almost undoubtedly due. Replacement of the rear sensor is possible if you have small hands. Replacing the forward sensor requires removal of the intake manifold. Once you commit to that, the hoses and idle stabilizer valve, and cleaning the injectors becomes part of the project.

Replacing the cam position sensor can be done without a lot of disassembly. It's mounted to the rear of the front right cam drive housing, next to the engine lifting bracket. The cable routing in that area is important, as the high-current wiring in the main engine harness is clamped to the same bracket where the cam position sensor wiring connector is mounted. The lifting eye bracket needs to be in between the cam position sensor wiring and the engine harness when all is secured.

Before you start replacing parts, get access to a Porsche diagnostic tool or one of the several aftermarket tools to confirm the sensor problems.

Juandotto

Speedtoys, thanks for your answer. I´m not obsession, jajaajjajja...., but cleaning the MAf I thought that was a possibility.


350 $ for a MAF is so cheap. Here, in Spain, a new MAF is 2000 €, and a rebuilt Maf is a 1500 €.


Dr Bob, thanks for your answer!!!! I´ll try to find another failure that you says.


I have decided not to clean the MAF, and research where is the failure, like knock sensors, cam position sensor, etc.........


Thanks!!!!!

Rexxus

hi speedtoys, Merlin and Dr.B.

im at the beginning of my research, just gathering info before I do anything (and I may bring it to a mech but hoping for your thoughts). I’m wondering if my car is running rich and or has sluggish acceleration. The hardest part for me is I’ve never driven another 928 so I’m not sure what it’s supposed to feel like and I’ve owned mine for a summer. So some items about the car;

89 S4 euro
fuel vapour smell coming from back of car. Washer was replaced On hex bolt. The smell is a LOT less but it’s still there. It’s typically after I drive and park in the garage. This might be nothing but it got me thinking today. Does your cabin smell like anything? Mine smells like “old car.” It definitely doesn’t smell like cleaning products, cologne or anything else except stale car. So it got me thinking, is that a lingering fuel smell that’s been penetrating the cabin with the PO for a while? My first thing to check now that a mech changed the washer is the fuel pump in the cabin. I’m assuming it should smell after I drive? And smell strong if I drive with the hatch carpet removed and then jam my nostril into the area? I’ll stop driving first though…

reading Over the forums, it seems it could be a MAF issue, possibly a fuel pump/filter. Air filter was changed recently.

the mechanic who did the PPI said the car drove well so I’m assuming it’s not something that can be missed? Is it obvious to any professional if a car is driving under powered, lean or rich? I mean don’t get me wrong, if I press the pedal down the car goes but it’s not dukes of hazard front of the car goes skyward and my *** is pressed into the floor. I’ve only filled up 3 times since I’ve owned the car so data is a little light but it seems like I get about 550km per tank of gas or about 7.45km/l. That could be wrong though, it’s just one reading.

the vapour issue is definitely the most pressing because it’s stinking up my house and really just ruining the experience so that’s a top priority. This might be an impossible question but how do your cars drive? Twitchy and light acceleration like driving a Yamaha R1 or more cruising with power like a Harley?

Speedtoys

Un plug the O2 sensor with a warm engine, a few minute after starting it

If it suddenly runs better, replace the O2 sensor.

Also, pull the vaccum hoses on the fuel system dampers, and the pressure regulator with the engine then off...do the lines smell like gas? Did gas drip out??

Lets start there.

928NOOBIE

I have used CRC MAF cleaner a few times and always had positive results. I soak it down with about half the can...really get to it. It helps.

Scott Peterson

Above 3500 the "Flappy Valve" is supposed to switch positions for more horsepower at higher rpm.
double check that it is working. or it will fell a little sluggish at higher rpm.

Speedtoys

How did a clean maf get cleaner?

Did you do it on the car? What air filter do you have?

Bosch ot wire MAFs dont suffer the same as kohlman vortex (spelling) for film style.

928NOOBIE

I take MAF off car. I use factory OEM air filter...get from Roger. Even have it installed right way. It does get it cleaner...perhaps there is some residue or something on the wires ...even though they get hot....I douse that sucker too...really give it a good going over...I squirt some on the inside walls of the MAF; outside the small cylinder where the wire is, just to clean off anything that could be hanging around...even though theoretically nothing should be there...but you are there so why not.

Seriously it works better after I do it. I don't do it on a set schedule...just kind of when I remember and if I have some cleaner handy next time I have the MAF off the car. I never see dirt or soiling on the wire...I just do it cause I got good results the first time I tried it. CRC makes a MAF cleaner; I'm using according to CRC the correct thing. I just spray it..I don't stick anything in there...just a good spray.

....let it dry thoroughly of course before putting back in...it dries quickly. I do not spray the electrical connection or anything on the outside of the MAF itself. The electrical connection only gets DeOxit...again usually when I remember and have the MAF off the car.