Multiple fried MAFs? check this

[KentSzabo]

When I had my MAF replaced on my '02 Golf by the dealer they said they had to modify the wiring harness as well. So I suspect the failures have something to do with the wiring.

[ October 25, 2002, 13:23: Message edited by: KentSzabo ]

 

[BoraTdi]

I got a new connector for the MAF which includes splicing new wires into the wire that GOES to the harness, but it looks like there is a deeper issue.....

 

[BoraTdi]

http://forums.tdiclub.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=3;t=009039;p=2#000041

My latest post re: fried ECU and no-start.

 

[BGUERIN]

I guess the whole MAF issue will never go away.I think everybody has their own theories at why this is happening and I think everyone is so confused about what is happening. We have bad connections,contaminated Maf's, dead mafs, mafs sensitive to vibrations ect....
If anyone really knew the real problem they would be rich. I've gone through three MAFs and my last one has about 75,000Km and it's still great. If the failures were consistent with exactly the same symptoms than we would be able to pin it down. I've even dropped mine 4 feet onto a cement floor with no problem. I believe it's more of a contamination problem. This is what I did to prove this point. On your air filter you have a little black tube comming in from the valves. get yourself a piece of white cotton sheet with the highest amount of thread count(Mom would know what I'm talking about). Take off your whole MAF assembly and put this at the input of the MAF and shove it back into the air box. travel about 100 miles(the car may go into limp mode before this,sine the piece of cotton may be plugged up). When you look at the sheet it is black. This unfiltered air comes from the EGR back to the air box and comes back through the MAf. This is done to burn off excess fumes to gives us cleaner air. Solution...... Take that little hose and place it just pass the MAF assembly(I took out the Tube from the MAF to the EGR and drilled a small hole and screwed in an small hose adaptor and plugged up the hole on the Air box(DO NOT USE SILICONE).
Now do the same test over. Place a new sheet over the MAF and go another 100 miles. Wait till you see the difference what oilly dirt is picked up and what you dont pick up. With this mod I have found no change in the performance BUT I sleep better nighta knowing I dont have this crap depositing on my MAF.

 

[mickey]

The world really needs a kit to adapt an A3 hot wire MAF to the A4 cars.

-mickey

 

[jmur]

BGUERIN, very interesting. Maybe this deserves its own post to attract some more attention. Anyway, I thought that tube was merely the atmosphere dump side for the various vacuum solenoids. I'm surprised to learn that it's a source of contamination. Maybe some of the solenoids have leakage? If so, connecting downstream of the MAF sure makes sense.

 

[BGUERIN]

If I had an easy way of posting pictures of this I would but I have had no luck. If I could send someone the pictures at an E-Mail address at home and they can post it this would be great. You wont beleive the crap after only 50 to 60 miles.

 

[wolfsburg]

I have thought about this and have what I think maybe a solution. Instead of drilling a hole past the MAF and reinserting hose, what about simply letting it hang free (fastening it to something) and using a PVC valve from another car that fits the hose size. Plug the hole in the air box with a plastic valve cover which are available at auto parts stores. Our store in the area, Crappy Tire sells a selection of sizes in a pack so it looks like that there will be one to fit. The only thing I need to find out is the hose size and then I am set. Cost about $8.00 Can.$ and it can be returned to stock in a minute. What do others think of this idea?? Yes pollution maybe increases but saves maybe the MAF. I just replaced the MAF in an out of warranty situation (78,000 km) that VW covered, part only (retail in Canada $500.75!!), but I am grateful for that. I let the dealer do the install, that way I have recourse again. Car had no power and when I disconnected the MAF wire, the car had lots of power again. Replaced fuel filter, told this to dealer and he said MAF is shot and it was. I have done the EGR mod. Car runs fantastic again. 2001 Jetta TDI.

 

[GoFaster]

You folks are all talking about the crankcase vent, right?

 

[wolfsburg]

Go faster: We are talking about ( at least I think so!!)a small rubber hose that goes into the air filter box just below and to the side of the MAF. The other end goes to a "T" one being the N18, EGR vacuum regulator solenoid valve and the other from the "T" going to the N75, wastegate bypass regulator valve. Any comments Go Faster?? We met at a Spring GTG on Racine. Thanks

 

[SkyPup]

That hose is the filtered air intake for the vacuum system, do not remove it, all the pneumatic acutators will be trashed out with filth.

 

[BGUERIN]

Before you come out with the conclusion that its filtered air you are partiallt right. Whats the difference if you install the hose just after the MAF rather than before the MAF. I see what you are saying I would not just let it hang with a PVC valve. The air is just as filtered pre or post of the MAF. Attempt to do the experiment with a high thread count piece of sheet with the hose were it is now ,than using a new cloth reperform the experiment with the hose after the MAF. Like I said I can post pictures of both if someone wants to give me an E-Mail address and they can try and repost on this thread. I can have the pictures sent to someone by Thursday.

 

[wolfsburg]

Skypup: You are right the the hose goes to the filtered part of the air box, but how do you explain what BGuerin has done in his test.Looks to me like the air is flowing to the airbox, but I'm not sure. Will have to make a trip to my trusty diesel mechanic and ask. Maybe your right! Thanks for your input. That's why I am asking these questions beforehand.

 

[wolfsburg]

What baffles me in general is that the Euro spec TDI must surely not have these problems as I cannot imagine the Germans putting up with this. And I am one of them! I asume they have much cleaner diesel at the pumps and maybe not as much pollution stuff. But to get back to the problem at hand. From the above posts I understand that the hose we are talking about moves air in both directions, otherwise the vacuum would not work and going the other way, the sheet from BGuerin would not turn black. My guess is that it moves in one direction, to the airbox and the dirt goes thru the MAF. It would have to suck lots of air to keep a vacuum. Because where else would the dirt on BGuerin's sheets come from. There are no other holes in the filtered part of the airbox. I'm confused...

 

[BoraTdi]

After 3 years of TDI fun, I'm burned out on having to do things like PVC-pipe science projects. I never thought I would say "I am considering an ugly Honda Accord" but I am giving it serious thought.

I drive too much to keep playing games with this turd.

 

[jmur]

Here's how I think it works. The pneumatic portion ot the N75 & N18 may be regarded as single pole double throw switches that allow an actuator diaphragm to be either connected to vacuum or atmosphere. The small tube going to the airbox is the atmosphere part of the circuit. Where does the contamination come from? Not the vacuum pump because the flow is toward (into) the pump. It must come from leakage in the actuators. Normally the actuators shouldn't leak but maybe occasionally one does and that may explain why some people have MAF problems and others don't. Whatever, inserting that hose downstream of the MAF seems like a good idea. BTW, if you plug the hole in the airbox, make sure that however it's done nothing can rattle off and take a trip down the intake.

 

[jmur]

Here's another thought. This forum is a worldwide, diverse distributed brain network, sort of like SETI@home except brains instead of computers. That being said, you would think we could figure out this MAF stuff together, right? It's a race SETI vs. TDIclub

 

[Paul @ RP Spec]

Mickey, our own 'Dutch' has designed a circuit to modify the Pierburg MAF signal to adapt it to the later model motors. Check it out @ http://www.geocities.com/tech4tdi/ seems to be a fairly simple circuit, and the response curves are a very good match.

[ October 30, 2002, 04:05: Message edited by: Paul @ RP Spec ]

 

[mdailyups]

Hey Wolfsburg,I have the same problem that you had with lack of power I disconnected the MAF and power came back .My question to you is will I damage my engine if disconnect my MAF until I can afford to repalce it.

P.S. I own a Maroon 99 Jetta A4 TDI

 

[mickey]

Paul: That's the solution! Ditch the A4 MAF entirely and go with something reliable!

This should be in the FAQ. (Maybe it is...I'm like the world's oldest newbie. I never "search." Nor do I ask directions when lost.)

-mickey

 

[mickey]

I assume that the "Pierburg" MAF is the hot-wire one from the A3?

-mickey

 

[BGUERIN]

I started to do the test over again. Again as stated the cloth filter I placed before the MAF is totally contaminated with a black soot. I drove 120 miles and as this filter was trapping the soot itstarted to block the air flow and hence the MAF is in limp mode(no CEL). I will do the same test today with the solonoid hose after the MAF. I attempt to hook up digital pressure meter and drive it like this to see what is happening. I tried to measure the pressure with the car standing still and there is a negative pressure from this hose as you increase throttle. It's very small something like -170mmHG. I'll try to set it up differently as to get better measurements. Whereever this stuff is comming from I feel it is contaminating the MAF. I seem to get a different result since i've changed diesle to Sunoco Gold diesel. The filter is not as black. So maybe using a different type of fuel may be causing this MAF to go dead. I'll keep you posted and should have all results and pictures by Friday.

 

[jjvincent]

I guess you could put an Old Beetle fuel filter in-line with the vent hose that goes to the airbox. No extra holes to put in the intake pipe either.

BGUERIN,
It might be a good experiment for you to do. Since they (the filters) are clear you can see all the contamination that goes through the line and is caught by the filter. This would better isolate where the dirt is coming from.

 

[wolfsburg]

All I use is Sunoco Golf and the MAF still died! It's the best but it still eventually gets covered in a oil coating.

 

[jjvincent]

I'm really confused, so I have a few questions:

1. How does different fuel cause contamination of the MAF?
2. How does dirt migrate through the little vent hose that is plugged into the airbox?

I must be overlooking something.

 

[BGUERIN]

Hey...I'm just as confused as everyone else is with this mysterious black dirt. Do you have a part # for this beetle filter? I'm even thinking of possibly putting in a check valve which I will do over the weekend and see if this stops the dirt from enretring the air box.

 

[jmur]

I'm taking that tube off of the airbox and installing small separate filters for the N75 & N18 valves. These filters are transparent with white elements so it should be easy to identify where the junk comes from. We'll see. Stay tuned.

 

[jjvincent]

I don't know the part number for the filter, but they were used for about every vw beetle, bus, ghia, audi fox, 100LS and Super 90 (with a carb.). I bet most parts houses still have some around. The part number might be 803 201 511E. They can't be any more than a couple of bucks. They are clear and have a paper filter in them. You can get a good look at the dirt they catch. Just remember to put the clear side away from the airbox (so you can see the side of the filter that catches the dirt).

 

[mickey]

1. How does different fuel cause contamination of the MAF?
2. How does dirt migrate through the little vent hose that is plugged into the airbox?

<font size="2" face="Verdana, Helvetica, sans-serif">1. It doesn't.

2. It doesn't.

A4 MAFs fail because they are a crappy design. Good theory...bad execution.

It doesn't matter what fuel you use, or what air filter you use, or how the planets are aligned. If you have an A4, it's a crapshoot whether your MAF will function from one day to the next. That's why adapting an A3 MAF is the best solution.

-mickey

 

[mailman]

I agree with Mickey. If you think about it, in order for an electronic device to survive in such a harsh environment (e.g., thermal cycles, vibration, etc.) it needs to be quite robust.

Or ... maybe the design is fine and the manufacturers just can't build it right.

Either way, may as well keep a healthy stock of TDI MAFs on hand for awhile....