MAF Graph Opinions

Hello!
I am just looking for some opinions on my MAF. I thought my car seemed a little sluggish recently (2002 Golf 5spd ALH). It has 225k miles, not sure if MAF has ever been changed.
I ran 2nd and 3rd gear pull, here is the graph:




And boost if anyone is curious

Yup, you've got it figured! New MAF time.

MAF is ordered, thanks!

Looking at those overboosts, I would take a guess you're going into limp mode here and there.

If it went into limp mode, there should be a code stored, right? No codes when I logged these.
I do plan on replacing all vacuum lines and was planning to check the actuator on the turbo next time I have the panzerplate off.
But overall, the car ran perfectly since I've had it, but recently I thought I noticed a little low on power. It is also quite smoky on startup (1 -2 seconds or so), but perfect after that.

What's the book on how to interpret these things?
They look normal to me.
You stomp on the pedal, requests for a bunch of air, air gradually rises to meet demand.
And boost seems about perfect.
But like I said, I really don't know what to look for.

From what I had read, the MAF actual vs specified should be a very close match. Looking at some references now, it does seem that the boost maybe over as well, like enabled said.
Maybe someone can chime in, do the charts in this thread look how they should: http://forums.tdiclub.com/showpost.php?p=2849149&postcount=4
Best reference i could find.

There is also the MAF101 thread that states:

The reading in the actual field should track with the specified field, and should go over 800 mg/H. In reality, the “800” reading needs to be sustained and not decay. This test should be performed under WOT and under a heavy load such as running up a long hill. If it does not the sensor is bad. Replace it.

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http://forums.tdiclub.com/showthread.php?t=148753

OK, I missed something here, sorry!

I was thinking that the first graph had boost (Blue line). Didn't see that it was Requested MAF (duh!). So, yeah, while Actual isn't attaining full max MAF numbers Requested max MAF isn't either. Should get at least 950.

In general one should be able to manage to get RPMs to redline from a stop (not in gear). If you can get there then it's a good bet that the MAF isn't restricting: boost is then likely something to consider.

Again, sorry for not paying closer attention.

I will just replace the MAF anyway for peace of mind, since it's a known failure point. It still does not seem to match what the various thread and reference docs say it should be doing I think.
I remember trying to figure an A/F issue out on a gasser once, what a pain, with the relationship between the MAF and the various O2 sensors. Just because one sensor reading is off, could mean that a different sensor is actually at fault, and nothing is even wrong.

Like I said, I will also replace all the vacuum lines and check the operation of the VNT actuator when I'm at it. I'll also have to check the intake for clogging. The PO told me he never got around to doing that.
I don't have an issue getting to redline, and there seems to be no difference in right after turning the engine off and on, so I don't think this is a full blown limp mode.

I think that you're headed in the right path. While at things I'd also suggest making sure your air intake path is clear- check for a clogged up snowscreen (may or may not have one- there's a relief port that's supposed to open up in cases were a snowscreen is clogged, but I wouldn't rely on it being as functional as a clean snow screen).

UhOh said:

I think that you're headed in the right path. While at things I'd also suggest making sure your air intake path is clear- check for a clogged up snowscreen (may or may not have one- there's a relief port that's supposed to open up in cases were a snowscreen is clogged, but I wouldn't rely on it being as functional as a clean snow screen).

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Good call, will add that to the list. It's getting close to air filter change time as well, so I might do that a little early, too. I don't like to open the housing to check filter if I'm not replacing it.

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Snow screen is at the grill end of the snorkel. The snorkel "plugs" into the air box: don't need to open the air box to remove it (just remove the two 10mm bolts) and then the 10mm nut that'll then be readily exposed holding the end of the snorkel.

Ok, so I did a little bit more work today since I got the replacement MAF.
1. Installed MAF, car had old style.

2. Tried to clean snow screen, it was not present. I do remember the PO mentioning that he tried to clean it and found it gone now.

3. Changed air filter. There was a fair amount of large stuff in there, feathers, leaves etc. So I think I would like to replace the snow screen. Is that possible?

4. Attempted to check turbo actuator. First I found I only have 10 inch hg, upon further investigation, I could hear a housing sound after I shut down the engine. Found the brake booster hose is cracked. I will get a new one. Maybe tonight I'll try to take it up temporarily and see if that resolved my issues.

5. How do you test the N75? When I do output tests, they are sequential and the one right before it's the fuel shutoff valve, so it can't be done with the engine running, unless I'm missing something.

6. Tried moving the actuator with my vacuum pump but I did not have a good seal, need to find a better fitting.

I might do a logging run now and then one after I take the vacuum tube to the booster to see if that isn't the major issue here.

Make sure all your vacuum hoses are good. If they are old, just replace them. Ill bet 9 out of 10 N75 valves get replaced when the problem was a vacuum leak from a bad hose.

Yep, was planning on replacing them all eventually. I think I found some good instructions on trying the N75, but first I need to fix the low vacuum problem.

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When you find and fix longstanding boost issues it's always a good idea to drain the intercooler before you put everything back together, just in case oil has accumulated in there.


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Thanks for the tip, Copa! IC is draining right now.

So I temporarily fixed the brake booster hose. I also found that the N75 is working correctly. The vane actuator does not work at all, it does not hold vacuum. I am able to move the rod by hand, not sure how much, though.

So I will order all vacuum hoses and a new actuator, and will see from there.

Is it OK to drive the car as is for now? Or should I leave it parked?

najel said:

Thanks for the tip, Copa! IC is draining right now.

So I temporarily fixed the brake booster hose. I also found that the N75 is working correctly. The vane actuator does not work at all, it does not hold vacuum. I am able to move the rod by hand, not sure how much, though.

So I will order all vacuum hoses and a new actuator, and will see from there.

Is it OK to drive the car as is for now? Or should I leave it parked?

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I would get the vacuum working correctly first before throwing guess parts in it.
This gets expensive quickly.

Measure the vacuum going to the actuator with the car running.
You need at least 20 inches vacuum for the actuator to go to full.
With a vacuum pump the actuator should start to move at 3 inches or so and be at full at 19 inches or so.

The actuator has to hold vacuum also.

wonneber said:

I would get the vacuum working correctly first before throwing guess parts in it.
This gets expensive quickly.

Measure the vacuum going to the actuator with the car running.
You need at least 20 inches vacuum for the actuator to go to full.
With a vacuum pump the actuator should start to move at 3 inches or so and be at full at 19 inches or so.

The actuator has to hold vacuum also.

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Right, I actually got about 20 inhg now at the vacuum out Port of the N75.
However, I attached the Pump directly to the actuator and pumped and nothing happened, it did not build our hold vacuum.

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najel said:

Right, I actually got about 20 inhg now at the vacuum out Port of the N75.
However, I attached the Pump directly to the actuator and pumped and nothing happened, it did not build our hold vacuum.

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OK, if it did not hold vacuum then the diaphragm is bad.
Easier and cheaper to change it then the entire turbo.
When you do change it there is an e-clip holding the rod on the turbo arm.
I found it easy to get off, easy to loose putting it back.
After loosing a few clips somewhere in the area I attached some sewing thread to the next clip to make it easier to find when it flew.

I went to Cal-Ranch and purchased 6 of the E-clips, also affectionately know as Jesus clips.
In my experience the first words out of the mouth when clip goes flying is, "Jesus...."

Thanks, I did see that note in the write up on the other TDI site as well. I read that 1/4" E clips work, so I grabbed a few at the hardware store to have around as spares. But the trick with the thread might be the way to go here!
Also ordered the 10 mm flex head ratcheting wrench (of course not available locally anywhere). I also did not have any luck sourcing silicone vacuum hose locally, they basically were all confused, only have silicone hose in 1/2" and up. So everything ordered from ID parts, should get around to installing it this coming weekend.

najel, IME the easiest way to remove the actuator is from the bottom and I have removed my actuators many times so here is my method:
1. get car up on ramps
2. remove cv joint heat shield
3. remove discharge piping from turbo/pancake pipe
4. remove two 10mm bolts holding actuator to exhaust manifold
5. remove c-clip
6. note length of actuator shaft before replacing vacuum pot
7. attach new vac pot to actuator connector
8. put c-clip back on
9. put bolts back in
10. re-attach discharge piping
11. re-attach cv joint heat shield
12. use vac pump to double-check actuator arm setting
13. with engine warm log N75% at WOT
14. N75% should be near 65% at WOT in third gear

So far so good. I've replaced the vacuum hoses, in the process I broke the Asv actuator. I'll have to give a replacement, for now I should be able to repair it temporarily.

The bigger issue right now is that the clip on the VNT actuator is rusted stuck, I can't get it to come off. Soaking in PB blaster now. Nothing is ever add easy at it should be.

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najel said:

Nothing is ever add easy at it should be.

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I regular refrain around my place is: "Maximum effort!" Seems that everything has to turn into a battle.

UhOh said:

I regular refrain around my place is: "Maximum effort!" Seems that everything has to turn into a battle.

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I know that feeling.
I changed 2 ballasts in my kitchen light to install LED lights.
Close to an hour.
Everything was open in 2 minutes.
I figured it should have been 20 minutes max.
Car repairs seem just as bad other then routine maintenance.

wonneber said:

I know that feeling.
I changed 2 ballasts in my kitchen light to install LED lights.
Close to an hour.
Everything was open in 2 minutes.
I figured it should have been 20 minutes max.
Car repairs seem just as bad other then routine maintenance.

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Some time back I cleaned the exhaust fans and ducting in my two bathrooms. Messy job. Knocked off one in a fairly short amount of time. Second one, however, was, as the refrain goes, "Maximum Effort." WTH? There was a wasp nest up in there and blocking the exhaust flap. This was, of course, up above some wheel-spoke like thing that wasn't removable- the nest wouldn't come down through it. Poke. Poke. Poke... It would only move around. "Brain storm!" Wet it! Spritz, spritz, spritz... Poke, poke, poke... Yuck! Water and crap everywhere! (I did, however, have some plastic sheeting down- that was done first off, to catch, no wasp nest debris, but the normal crud you'd expect to come out)

In theory things should be fairly easy. In theory reality doesn't exist!

Oh yeah, for car repairs I work really hard to find a way to ensure that the job takes longer! Working on the wife's car I was quite pleased to have gotten a good system in place to drop and reinstall the transmission (clutch job; was also doing a suspension refresh). I was so pleased and excited at how well it worked I forgot to install the clutch fork! Pulled the transmission back out (I'd only just snugged it up to the block), installed the fork and thought: "Ah ha! So, there! Piece of cake!" Get the transmission back to the block (in record [short!] time) only to have Mr Murphy show up (again?). One of the plate's ears, goes around the centering dowels, somehow managed to fold over. I am very thankful that I caught it before I got any further (just going to tighten the bolts). So, I managed to save and then kill a bunch of time. BUT, I didn't injure myself, which one should always feel thankful for/about.

Yeah, there are lots of instances where things just aren't designed with maintenance in mind. Actually, I prefer working on the car much over working on most household appliances and fixtures. On the car, at least, there is often one correct way somethings should be, while the household items seem to be very finicky with getting things adjusted/aligned just right, etc.

UhOh said:

BUT, I didn't injure myself, which one should always feel thankful for/about.

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That is very true, good thing to keep in mind.
Anyway, back to my issue. Everything back together properly, I think I adjusted the actuator properly, it started to move at about 4 or 5 inHG, and bottomed out pretty much spot on at 18. However, i am still seeing an overboost (although now it's more consistent than before). See this chart:

The data are found here if interested.
So what is going on? My theories:

1. Bad MAP sensor? I think it's very very rare for those to go bad, though, right?
2. Need to re-adjust the actuator? Do I make it longer or shorter to lower boost? Can't quite wrap my head around how it functions still
3. The vacuum on the vac in port of the N75 is lower than the system vacuum. At the main port, I meausred 25 inHG, at this line 15 I think. I had to use a generic check valve from the parts store, maybe that's the issue? It's hard to see with the inspection mirror for sure, but I thought the rod goes through full travel.

One other question - is this safe to drive if I keep an eye on boost? I have Scangauge, what max should I shoot for on the MAP sensor?

I drive my car watching the boost gauge every time I take off.
I still have to lengthen my actuator rod to limit the boost spike when I take off.
I can easily get 20# (US) boost and sustain it at mid throttle (or so)
If I ease off the pedal it will drop and stay down 5 to 10#
Vanes probably sticking a bit but I don't think that causes the high boost.