’03 Jetta has lost power

I have a 2003 Jetta that has me stumped. It has 220k miles on it, all of them mine, and until now has run like a champ. Recently it has started having problems maintaining speeds and climbing hills. It had a new timing belt at 190k, it has new filters all around. The boost has been checked, as have fuel injectors and their timing. The MAF was replaced less than 2k miles ago. The EGR and intake have been removed and cleaned in the last 1K miles. It’s throwing no codes. I live in UT and there are some decent changes in elevation from city to city but when it can’t climb a hill at more than 25 MPH, I get frustrated. It seems to be worse on the commute home when it’s ~100F.

I think the next step is to pull the catalytic converter off and see what happens but perhaps that’s not a good next step? Looking for suggestions.

Got VAGCOM?

Is it smoking when it bogs down? If not it is getting as much air as it needs to burn the fuel. The question then is why is not enough fuel going into the engine?

There are only a handful of reasons why that can be the case -- either fuel is precluded from going in (e.g. restriction in the line causing excessive vacuum), the pump is failing to deliver the fuel being asked for, or the computer is not asking for the fuel (e.g. restricted airflow somewhere and the computer is cutting back the fuel.)

Tell us more; what is MAF requested and actual? Can you get a value for both over 800 on Vagcom with a full-throttle run in 3rd and 4th gear from 2,000 RPM to at least 4,000? What is boost and is it steady or does it spike and cut back (MAP, or manifold absolute pressure) on the same run?

I know you recently changed your fuel filter, but thats where I would try next. Maybe a bad filter, o-ring, T-Stat.

Genesis said:

Got VAGCOM?
-I don't have a VAGCOM, maybe that should be next.
Is it smoking when it bogs down?
-It is not smoking when it bogs down.
If not it is getting as much air as it needs to burn the fuel. The question then is why is not enough fuel going into the engine?
There are only a handful of reasons why that can be the case -- either fuel is precluded from going in (e.g. restriction in the line causing excessive vacuum), the pump is failing to deliver the fuel being asked for, or the computer is not asking for the fuel (e.g. restricted airflow somewhere and the computer is cutting back the fuel.)
Tell us more; what is MAF requested and actual? Can you get a value for both over 800 on Vagcom with a full-throttle run in 3rd and 4th gear from 2,000 RPM to at least 4,000? What is boost and is it steady or does it spike and cut back (MAP, or manifold absolute pressure) on the same run?

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Few answers in the above quote. I don't think I have enough data.
I took it to Streamline in SLC who threw it on their VAGCOM. I have no values, just an assessment of "normal" but they didn't think it felt right either. That was couched with, but we don't usually drive diesels.

Well, if you have no smoke and yet power is way down, and you don't have VAGCOM (not a generic "code scanner") then your diagnosis capability is rather limited.

I'd unplug the MAF sensor and see if the power comes back. I know you said it was replaced, but....

If it doesn't then you need to find someone who can take a look at what it's doing with VAGCOM while you drive it. You're either not getting fuel because the car is incapable of injecting it or there's a reason that the ECU is not calling for it. Either way if it seems to be firing ok (the engine is not misfiring or misbehaving, other than being woefully short on power) there's a limited list of possible reasons.

I'd find someone local to you with VAGCOM and see what you got, although the MAF-unplug test is one you can do easily and quickly.

Yes, agree with Genesis. Start with the simplest things first.
Unplug that MAF and see what happens. Perhaps the new one is faulty or it wasn't the correct one? Intake/airfilter should be checked again. The snowscreen at the inlet wasn't mentioned. Remove it or make sure its clean.
Turbo and/or actuator perhaps, Although I've driven my TDIs w/o any boost and while it makes a big differenece, they still have better power than you are getting. Recently there was a case of someone who had very low power such as you describe and the turbo shaft had broken and the turbine wheel was laying in the case, blocking exhaust path. That's pretty easy to check, esoecially if you can get it on a hoist.
Bad tank of fuel clogged up that "new" fuel filter or an obstruction at the fuel pick up unit inlet?? Also pretty easy check if the fuel tank isn't full.
Keep updating, please!

Ok, sorry I'm slow to update:

This weekend I pulled off the MAF but that didn't seem to do it.

I took my car to a guy who does exhaust/catalytic converter and asked him if he thought I should replace it. I think he's going to try pulling it off first. He said when he ran it hard and then checked the exhaust that the system between the turbo and the CC were extremely hot but that he could touch the system behind the the CC. He said he could identify a lot of build up in the part of the system. He's thinking he'll pull it off and see how it does. I was going through the service manual and it says that my TDI doesn't have a code for catalytic converter that will throw a check engine light so that could explain the lack of input from the car.

Waiting to try this and I'll update again.

I think before they take the cat/pipe off, I would check the turbo to see if its seized or OK. A turbine wheel shaft broken with a wheel stuck against the case would be similar to an exhaust obstruction.

julieinogden said:

If I can hear the turbo spin-up, am I naive to assume its ok?

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If its spooling up it must be working. Hard to believe it would spool up well with exhaust/cat blockage.
Edit: I see in original post the boost levels had been tested. My oversight.
Ever get to check the snowscreen or the fuel pick-up inlet??

Snowscreen has been checked, just didn't know it was called that until I searched.

How does one check the fuel pick-up inlet?

julieinogden said:

Snowscreen has been checked, just didn't know it was called that until I searched.

How does one check the fuel pick-up inlet?

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Wait til the fuel tank is nearly empty. Flip up the rear passenger side seat base. Remove the inspection cover and remove the fuel line connectors. Unthread the big plastic retaining ring and lift out the pickup unit. Examine the pickup tube.
There is a how to thread about how to remove the check valve (which the '03 doesn't have) that has pics and instructions, but its quite easy.

I just did that to my 2000 Beetle. Seems to help some. Be VERY careful lifting the black ring up...you have to lift up the two plastic fuel lines to remove ring. When I did it kinked one of the fuel lines up.. l was lucky. It didn't break it and I got a pair of pliars and put eletrical take around each jaw. Then I gently squeezed the kink a little to get it close to round again.

Today's updates:
New fuel filter didn't fix it.

New air filter for good measure didn't either.

Haven't dug into the fuel intake inlet yet but on the list.

Borrowed a friends Edge, which is not VAGCOM but measure some similar things, thought it was interesting that the Map would rise to 26 with the pedal on the floor and then when the RPMs hit about 3500, it's drop to 17 and slowly climb back up. Seems to depend on the incline though. On slightly less of an incline it held 25, MAF read 43. The baseline MAP reading was 12.

Local Mechanic, who also drives a '03 TDI, thinks its the turbo. I'm less confident. Any thoughts? He can't work me in for 10 days and I really don't know what it takes.

It's not the catalytic converter, straight pipe didn't solve it.

Your clutch could be slipping.

julieinogden said:

Today's updates:
New fuel filter didn't fix it.

New air filter for good measure didn't either.

Haven't dug into the fuel intake inlet yet but on the list.

Borrowed a friends Edge, which is not VAGCOM but measure some similar things, thought it was interesting that the Map would rise to 26 with the pedal on the floor and then when the RPMs hit about 3500, it's drop to 17 and slowly climb back up. Seems to depend on the incline though. On slightly less of an incline it held 25, MAF read 43. The baseline MAP reading was 12.

Local Mechanic, who also drives a '03 TDI, thinks its the turbo. I'm less confident. Any thoughts? He can't work me in for 10 days and I really don't know what it takes.

It's not the catalytic converter, straight pipe didn't solve it.

Click to expand...

You can verify for sure w/VCDS, but kind of still sounds like a bad MAF. They don't all fail w/the same syptoms. Somewhat like my '03 project after I got it on the road. It too, didn't seem bad with the normal unplug it test. I swapped it with the new one in the '01 and it made the difference.

The values you give for the Edge scan tool don't seem to be quite compatible. MAP at idle should be about 13.5 (+/- depending on elevation and/or barometric pressure) and since youre at elevation, I assume, that may be about correct. Should go up to 30+ on a 3rd gear wide open pull to max rpm. But even after hitting a limp mode condition (no boost) the TDIs I've had will still give better performance than you are getting. Has anyone pulled the hoses off the turbo and had a look yet. Pretty easy and quick exam.

Reading thru this post again. When it was scanned w/VCDS, did they really look at the timing graph?? Perhaps the IP sprocket bolts have allowed the pump sprocket the slip and timing is now badly retarded.

To test the clutch, I set the cruise to 71 mph and ran it over hills. Never dropped the cruise so I think my clutch is ok. I was pushing it harder than I usually do coming home during the cruise control test. Then about ten minutes in, my glow plug light started flashing. Proceeded to flash for the next hour of driving. Turned it off let it cool off for an hour and a half, fired right up with no flashing. I figured that meant some sort of code had been generated. PO228, Throttle position sensor, and PO299, Super charger under boost condition. I suspect one may cause the other but I don't really know what I'm into. One thread about p0228 suggests that "high limp mode" parallels the symptoms I saw. A turbo seems like a big investment when I read about N75 valves and actuators giving similar symptoms/codes in other threads. Where would you start? I need to ask to borrow a VCGS from the guys who worked on the car so I can get a reading to post but I don't know what the probability of that is.

A flashing GP light isn't a engine system error. Usually relates to a failed brake light switch, burnt out brake/tail light, which may result in cruise control fault.
If you are going to own a TDI for any length of time, you might as well pony up and buy VCDS. Or else you will probably be borrowing it often.