P0401, P0103, exhaust leak, Low power

I have a 2002 New Beetle that has developed an issue. After driving for a good 20 minutes or so, it will sometimes have almost no power. it will also sometimes do it in a manner that makes the car jerk repeatedly at speed. as if power is coming and going. I only know about the exhaust leak because i saw a column of sooty exhaust come out from behind the engine when i started it, checking this problem. I pinched off the vacuum tube controlling the egr to see what that did, power loss happens less often, it is better but still not fixed. I do not have a vagcom, i only had a generic scanner. it showed me 12g/s at idle for the maf, 24g/s and it didn't really go higher than that as i revved it. I converted that to mg/stroke and it's "in spec" at idle, but the mg/stroke actually drops at higher rpm's. When it loses power while driving it will struggle to go above 3000rpm, and it doesn't even try to down shift. it will always redline in neutral though. This car also has a P0740, and has had it for awhile now.


What exactly are POSSIBLE causes? My theories are stuck vanes, bad maf? (cleaned it), clogged intake? (i was told the egr had been changed before we got it, it used to act like the "turbo doesn't spool", which sounds similar to this.), could a vacuum leak cause it? If the turbo was not always responding, and that is the problem, would there be a code for lack of boost?

The good ole Ross Tech wiki gives some clues.
We see a lot of these being bad wire/connect as the cars get older. The ECU sees what it sees, reports errors. It is not comprehensive.

sober_lime said:

What exactly are POSSIBLE causes? My theories are stuck vanes, bad maf? (cleaned it), clogged intake? (i was told the egr had been changed before we got it, it used to act like the "turbo doesn't spool", which sounds similar to this.), could a vacuum leak cause it? If the turbo was not always responding, and that is the problem, would there be a code for lack of boost?

Click to expand...

There are many 'POSSIBLE' causes.

The car could be going into limp mode which shuts the turbo control off.
Simple test when it happens is turn the car off for a few seconds, re-start, and see it the power is back.

Do you drive the car easy?
If so the turbo can be carbon'd up.
You have to push it occasionally to keep it cleaner.
I use to do a trophy run every day leaving for work and returning when I got on the highway.

If your vacuum isn't producing 20 inches of vacuum the turbo actuator can not be fully pulled.

A hand vacuum pump is the best diagnostics tool but a plane gauge can help.

With the pump you can check it the actuator is starting to move at 3 inches and full at 20 inches.

You can also take the actuator off to check if it' full of rust. There is a VW TSB about this.

While it's off you can also move the arm going into the turbo to see if it's free, moves easily w/o sticking, and moves the full range.

Last, you really need VCDS to properly diagnose this.
Not a generic code reader.
There is a lite version that's free and can do what you need for the basic diagnostics.
See: https://www.ross-tech.com/vcds/download/
Do you have a laptop to run this on?

wonneber said:

There are many 'POSSIBLE' causes.

The car could be going into limp mode which shuts the turbo control off.
Simple test when it happens is turn the car off for a few seconds, re-start, and see it the power is back.

Do you drive the car easy?
If so the turbo can be carbon'd up.
You have to push it occasionally to keep it cleaner.
I use to do a trophy run every day leaving for work and returning when I got on the highway.

If your vacuum isn't producing 20 inches of vacuum the turbo actuator can not be fully pulled.

A hand vacuum pump is the best diagnostics tool but a plane gauge can help.

With the pump you can check it the actuator is starting to move at 3 inches and full at 20 inches.

You can also take the actuator off to check if it' full of rust. There is a VW TSB about this.

While it's off you can also move the arm going into the turbo to see if it's free, moves easily w/o sticking, and moves the full range.

Last, you really need VCDS to properly diagnose this.
Not a generic code reader.
There is a lite version that's free and can do what you need for the basic diagnostics.
See: https://www.ross-tech.com/vcds/download/
Do you have a laptop to run this on?

Click to expand...

It gets a decent amount of full throttle, I don't have a windows laptop, but i might try a mac with boot camp, other's on forum seem to have luck with that. I might try to rent one of those hand vacuum tester's, too.

sober_lime said:

It gets a decent amount of full throttle, I don't have a windows laptop, but i might try a mac with boot camp, other's on forum seem to have luck with that. I might try to rent one of those hand vacuum tester's, too.

Click to expand...

A Harbor Freight MityVac clone does fine for vacuum system checks. Reasonable $, too.

Ok, so i got a vcds lite and connected it, according to it, my maf reads a constant 1275 mg/str. my boost pressure is fairly accurate, creeping about 200 mbar over specified (or requested) at around 3000rpm, but exactly as specified at and around idle. if i unplug the maf it reads as 550mg/str (the default i've seen mentioned) so my vcds itself must be reading the ecu right? Does it sound realistic that my maf is reading that high? My map reads about 985mbar constant, dropping a little with throttle


When i drove it (i originally was just in park in the driveway.) when it was stuck at 1275, the would run very rough at anything above idle. it eventually started to drop (the maf reading0 and it even seemed to reduce WITH engine rpm? but it still never ran right. eventually i just unplugged the maf, and it ran fine with low power, i drove it like that for a little bit. boost got up to at least 2100mbar, and stayed with the expected boost. than i turn the car off than on again with the maf plugged back in, and it stayed at 550, as if it wasn't plugged back in.


It seems i need a multi meter? Is this wiring or the maf itself?


It's also dropping to 0 sometimes when driving too apparently











WAIT, i might have solved it. I did the cage mod mentioned else where on this forum, and than i used zip ties from a few angles, because the connector wouldn't lock on, to hold it all together. the idle reading is still high at about 450, but it's reading perfectly now while driving. My connector had broken bits of the red piece inside of the connector, which could be why the cage mod helped?


EDIT: No, it's doing it still. it seems to only start acting up when warm. i must not have driven it enough originally to tell. I need to get under it