Replaced MAF, VCDS still shows bad

I tested my MAF a few days ago with VCDS and it showed that it was bad. Punched it in 4th gear at around 2000 rpm up to over 3000 rpm. MAF requested was in the 800s but MAF actual was in the 500s. It would sometimes go to 700 but quickly trail off.

I replaced the MAF with the new style from metalmanparts.com. Same result. Power did not increase, so I hooked up VCDS and go the same readings as with the old MAF.

I checked the wire harness and was getting 12V between pins 2/3 and 5V between 3/4. Air filter isn't new, but I blew it out with air. It is a little soiled but not bad.

Any Ideas?

Record the data. Go in 4th gear from 2500 RPM to 3000 RPM. At 3000 RPM it should be 800-900ish.

Post the graph.

Just hooked up VCDS and got this Fault code

1 Fault Found:

16486 - Mass Air Flow Sensor (G70): Signal too Low
P0102 - 35-00 - -

Running data now. I'll reply with a graph.

EDIT: I forgot that i started the car with the MAF unplugged and this is why I got the fault code. I have no fault codes now. 6/30/2009 8:23 AM CST

Yes, it is still showing pretty darned low.

Check the contacts, clean them if you can. You could attempt the "Cage Mod" But it's nothing more than dielectric grease, which shouldn't do much at all really.

Here is a short quip from Ross Tech's Wiki:
http://wiki.ross-tech.com/index.php/16486/P0102/000258

You may end up having to replace the MAF again!

Do you think it is worth it to check for any leaks downstream of the MAF? Also, is there something my car is doing that is hurting the sensors, or was I just unlucky and purchased a defective part?

Is the intake severely clogged up?

I have no fault codes. I forgot that I had started the car with the MAF unplugged, so that is why the code was on there before. It is now cleared and has not shown back up.

As for the intake being clogged, I have no idea. Is the only way to tell that by taking the manifold off? Should i check for leaks in air lines first? Pulling the intake seems like a lot of work if I haven't gone through the more simple items first. After work tonight I am going to try to find any vacuum leaks. About how long does it take to do an intake cleaning?

My car has only gone into limp mode one time and that was about 10 months ago when i was driving in the hills of Tennessee. The only driveability problems I really get are the slow accelerations when i give it 100% throttle, which makes sense by what the VCDS shows with the MAF vs RPM graph.

It takes all of 30 seconds to check the intake. Just remove the hose going into the manifold and take a peek with a flashlight.

oilhammer said:

Is the intake severely clogged up?

Click to expand...

Is this "severely clogged"? haha!

Wow. That's some clogged.

If you thing that's bad, wait until you get that egr valve off. It's probably worse beyond that.

at 75,000 miles i didn't think it would be this bad. Would running a failing MAF for 6 months cause more than normal buildup?

Welcome to the "weak link" in the fuel-air-oil from CCV system! Time for surgery. Your MAF wants to work but can't. I would clean the intake, then try again with the new MAF. Ah, what memories...and I did it at 46K !! You will spend most of your time cleaning the intake manifold. Do a search, lots of help and even gross photos!

And that is why your MAF voltage is always low. ECU does not have the 'intake clogged' logic in its programming. It assumes if the engine is at X RPMs, and the EGR duty cycle is Y, then the MAF flow should be Z. But Z cannot possibly happen if your intake is clogged 80% shut.

Now, you will need to REMOVE the intake manifold to properly clean it. Hot tank is best, but there are other dirtier methods that work as well. Once you get it back together, take it out and drive the crap out of it. It will smoke like a tire fire for a bit, due to the ECU's sudden spaz-out over how to fuel now with this suddenly appearing air and boost it has to work with now. But that's OK, it will settle back down and start working normally again.

BTW, so long as you use ULSD fuel, that level of clogging is unlikely to ever happen again.

I planned on going on a road trip this weekend (~1000 miles roundtrip). Is it ok to drive that far with an intake like that? Will it damage my new MAF sensor in any way?

I ordered the gaskets from tdiparts last night and expect to tear into it early next week. Thanks for all the input! I appreciate it.

IMHO it is ok to drive it you will just be underpowered all the time.

I cleaned my intake yesterday.

Post clean test drive....was like driving a new car! Higher RPM response was terrific. I didn't test with VCDS because it was pouring down rain, but I am sure results of the MAF test would reveal no problem with the MAF anymore.
After being a TDI owner for only 20k miles, I was convinced that maybe they were just a little slow. All I can say is, I probably never would've known the difference if it wasn't for this forum. Thanks!
I am curious as to how much effect the lack of airflow had on my fuel mileage. I'll have to wait a little to test that because my foot's probably gonna be on the floor for a week or so!

Way to go! You are now an official gunk head! Enjoy the new found breathing and power.

Great stuff, glad to see you got to the bottom of the problem. I wouldn't hold your breath on the ULSD thing as we have had it in the UK for some time.
I removed my EGR valve last weekend and was disgusted at the amount of cr*p in side, I guess it was about 3mm thick.
My car is a 2.0 A3 TDI "BKD engine" which has covered 40,000 miles. It has been serviced regularly and I have always used "Millers diesel clean" with every tank full of diesel.
I guess it's keep cleaning those inlet parts for us!!
Regards
Phil.