2004 BEW Jetta TDI - Low Power (possible Limp Mode)

irsean · Feb 24, 2011

I have a Jetta that has low power like it's in limp mode. I don't have any diagnostic equipment except a Code Reader (P0102). Did a lot of "low power" trouble shooting. Still need to trace wiring and vacuum to MAF. Replaced MAF.
The things is, when I unplug the MAF sensor, the engine picks right up. Plug it back in, no power (can slowly acc. up to 50 MPH).

Tomorrow I will start tracing wiring but does this sound familiar to anyone (unplugging MAF sensor and problem goes away)?

2004 Jetta TDI 1.9 (BEW)
Tiptronic Trans

PDJetta · Feb 25, 2011

I read here that with the ALH engines if power came back with the MAF unplugged, this indicated a bad MAF sensor. The BEW may be the same.

The ideal thing would be to spring for a VCDS scan tool and then read the fuel and air requested vs. actual amounts and possibly log them.

I would also check the actual vs. requested boost levels.

--Nate

DanG144 · Feb 25, 2011

Buy a new MAF. You need at least that, if power came back with no smoke when you unplugged your MAF.

irsean · Feb 25, 2011

I already replaced the MAF. That's why I'm looking at wiring today but, thanks anyway. I was just hoping soeone would have some insight as to why even a good MAF being unplugged would inprove the cars performance. Maybe I got a bad MAF (it wasn't Bosch).

DanG144 · Feb 25, 2011

When you unplug the MAF, it uses a default air flow number, often 550 mg/stroke on stock ones, higher on most tunes (set by tuner).
Fueling is limited by air flow (among other things), so if your car runs better with the MAF unplugged then the reported air flow from the MAF is lower than the default air flow.

irsean · Feb 25, 2011

I so need to get the VCSD.

jcrews · Feb 25, 2011

Check the heater power supply and reference.

Pin 2 (black/lilac) should be 12V with the ignition on. Terminal 3 should be 5V above common/ground. Pin 5 should be shorted to ground. You may have to have the engine idling to check the 5V source.

DanG144 · Feb 25, 2011

You can try to find someone in your area that has one, and will use it for you.

You might do a google search of this site for towns in your area, and "VAG-COM VCDS" . You can do that by choosing search from the blue ribbon above this thread, then advanced search, scroll to the bottom for the google search.
When you unplug the MAF, does it run normally? No excess smoke?

PDJetta · Feb 25, 2011

irsean said:
I already replaced the MAF. That's why I'm looking at wiring today but, thanks anyway. I was just hoping soeone would have some insight as to why even a good MAF being unplugged would inprove the cars performance. Maybe I got a bad MAF (it wasn't Bosch).

Was it a MAF sensor for the BEW TDI and not an ALH or a gas VW engine?

--Nate

irsean · Feb 25, 2011

MAF sensor is on a BEW (TDI-PD).

Didn't see if there was smoke when MAF sensor was unplugged but the car ran great without it and goes back to limp mode when plugged in. Can't reset limp mode. But it definitely is limp mode (sudden loss of power, accelerates slowly up to 40-50 MPH. No sputtering (leaks in vacuum/turbo).

DanG144 · Feb 26, 2011

If the actual air flow was as low as your MAF was reporting (say from a bad turbo or blocked intake) then it would run better with it unplugged, but smoke badly at high fuel. If it does not smoke at high throttle then you at least have reasonable air flow (and it may even be normal).

If you could borrow the use of a VCDS system, it would help a lot.

Search as mentioned above, Use the VCDS locator tools that are available (but very poor.) This thread gives some options. (Improving all the time.) VCDS locator

And I would post in the regional forum.

JB05 · Feb 26, 2011

Could this be an EGR problem?

irsean · Feb 28, 2011

Just ordered my VCDS system. I wonder how this will run if I put it on a Netbook.

CopaMundial · Feb 28, 2011

irsean said:
Just ordered my VCDS system. I wonder how this will run if I put it on a Netbook.

Will run fine on Netbook, I would even venture to say that's what most people put it on.

Uwe said:
Netbooks rock for VCDS. I can't remember the last time I used a "real" laptop in a car.

-Uwe-

I'd say you could trust his opinion on the matter as he is 'the creator'.

AARodriguez Corp. · Feb 28, 2011

The manual '04 that I have had a turbo with single broken compressor fin, it had low power, no smoke.

irsean · Mar 5, 2011

Got it! Now I get to play with it for awhile. Will be coming back with screenshots. Now, I'm actually glad this happened. Gave me an excuse to buy the thing.

Dimitri16V · Mar 5, 2011

irsean said:
I already replaced the MAF. That's why I'm looking at wiring today but, thanks anyway. I was just hoping soeone would have some insight as to why even a good MAF being unplugged would inprove the cars performance. Maybe I got a bad MAF (it wasn't Bosch).

check the intake past the MAF for leaks. the MAF measures the air and feeds the ECU that info, if the engine is sucking air past the MAF , it will report a lower value to the ECU. I would start with the intake hose elbow in the turbo.how is the air filter ?

Skuller · Sep 30, 2018

2004 TDI BEW Jetta Wagon vacuum at turbo line

The MRS' TDI Jetta has no zoom.
Leaks on turbo hose was fixed with a dog collar, and it worked great (I'm told).
Suddenly runs like there's no boost. Actuator holds vacuum.

I checked the vacuum (mini-vac) at the turbo line while at idle. I figured it would be 2-3 in/Hg.... NOPE! It was at 20, which means at idle the turbo should be producing considerable boost.

Any ideas? A bad N75?

-Skuller

2004 BEW Jetta TDI - Low Power (possible Limp Mode)

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