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VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old October 9th, 2019, 05:20   #16
oilhammer
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Was it a Bosch reman alternator that was installed? If not, then I would get the whole thing. If it was, then it may not be the problem, but in my experience, my charging system diagnostics are pretty quick once I open the hood and see a non-OEM unit there.

However, you can check the harness to the alternator for bad connections. It plugs into the car on a holder above the starter (the small wires...two go to the alternator, two go to the compressor), and the large wire goes straight to the fuse link box above the battery, on the far left as looking down on it from the front. Those fuse link boxes often melt, too, especially if the battery will not take a charge.
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Old October 9th, 2019, 05:34   #17
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Was it a Bosch reman alternator that was installed? If not, then I would get the whole thing. If it was, then it may not be the problem, but in my experience, my charging system diagnostics are pretty quick once I open the hood and see a non-OEM unit there.
However, you can check the harness to the alternator for bad connections. It plugs into the car on a holder above the starter (the small wires...two go to the alternator, two go to the compressor), and the large wire goes straight to the fuse link box above the battery, on the far left as looking down on it from the front. Those fuse link boxes often melt, too, especially if the battery will not take a charge.
Haha. It was whatever German Auto Parts was selling at the time, I believe a Bosch. I checked the connection at the alternator itself and where the fuseable links are but I haven't checked in that area above the starter. I remember what a nightmare it was sorting out a charging issue on our b4 Passat TDI. It took me a month to realize that the connector at the alternator was not fully seating. In that case I was getting an alternator charge light. Also got one when I changed it on this car. Strange I'm not getting one now. Thanks Oilhammer. I'm going to get the multimeter and do some reading once the battery is boosted.

Last edited by intro; October 9th, 2019 at 13:41.
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Old October 9th, 2019, 10:57   #18
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If it is the alternator, which was replaced about 4-5 years ago (about 30k miles or so), is it possible to replace just the voltage regulator? I had learned to do this on our Passat and it was a good deal less expensive.
If the regulator is bad it can be replaced.
Probably similar to the Passat.

Maybe measure for AC voltage with the car running and lights and AC on.
I would not want to see much but it would indicate a bad diode.
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Old October 9th, 2019, 11:08   #19
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You really need a proper scan tool first. Although at least the basics of the charging system can be checked with a volt meter. You do not need to go anywhere for this. Even a cheap volt meter will work. It is either charging or it isn't (most likely, that is usually how Bosch alternators work).

If you turn the key ON, the battery light should come on. If it does not, you may have a field wire problem (the above mentioned harness that plugs in atop the starter) or the alternator itself.

You need a gauge to check the fuel pressure, but again, like the alternator, my experience is usually the pumps work or they don't. There is a fuel pump relay, 409 I think, located inside the car. Provided your door latch microswitches are working correctly, that car should briefly energize the fuel pump when you open the driver's door. If you listen carefully you can usually hear it click back off after a second or so.

Those relays sometimes fail. But again, they usually fail and stay failed, or may begin to work again after the car sits. They do not fail "half on".

If the car has been sitting, you could have some varnish from old gas getting stuck in the fuel filter, as well as the injectors, especially if it is the returnless system (not sure which your specific car uses).

If the battery is fully charged, and can maintain at least 11v or so with the car running even with a bad alternator, the car should run just fine for a little while at least.

I think you likely have several problems, might be related, might not. But best to try and address them individually at first. Since the charging system is important, and isn't directly tied into the engine management for proper function in terms of allowing the engine to run, and it is fairly simple, I'd go after that first.
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Old October 9th, 2019, 14:57   #20
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Picked up the battery from Interstate. I dropped it off at 10 and picked it up at 4. Not sure what time they put it on the charger but when I went to pick it up the knowledgeable guy from inside the warehouse had left for the day and the young kid at the counter went and got it. Put the voltmeter to it and said "12.2- fully charged." Ummm, I debated that it should be 12.8 but he said I'd be able to start the car. He offered to keep it on the charger overnight which is how I've normally done it I think but I wanted to get home and check the charging system. After starting the car I was down at 11.8. With headlights, radio, HVAC, garmin, dome light, and hazards on, it dipped down to 11.3, and when I shut all those off again but left the car running, I was now at 11.5. Clearly, I have a charging issue. Wiring and plugs looked ok. Haven't tried cleaning up grounds. Battery indicator bulb lights up on ignition turn. Pretty disappointed if a new Bosch has given up after only 3.5 years. The good news: the throttle has come back and I'm not getting any new, random warning lights. I'll probably pull the alternator and have it bench tested just to rule it out.
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Old October 10th, 2019, 19:31   #21
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You really need a proper scan tool first. Although at least the basics of the charging system can be checked with a volt meter. You do not need to go anywhere for this. Even a cheap volt meter will work. It is either charging or it isn't (most likely, that is usually how Bosch alternators work).
If you turn the key ON, the battery light should come on. If it does not, you may have a field wire problem (the above mentioned harness that plugs in atop the starter) or the alternator itself.
You need a gauge to check the fuel pressure, but again, like the alternator, my experience is usually the pumps work or they don't. There is a fuel pump relay, 409 I think, located inside the car. Provided your door latch microswitches are working correctly, that car should briefly energize the fuel pump when you open the driver's door. If you listen carefully you can usually hear it click back off after a second or so.
Those relays sometimes fail. But again, they usually fail and stay failed, or may begin to work again after the car sits. They do not fail "half on".
If the car has been sitting, you could have some varnish from old gas getting stuck in the fuel filter, as well as the injectors, especially if it is the returnless system (not sure which your specific car uses).
If the battery is fully charged, and can maintain at least 11v or so with the car running even with a bad alternator, the car should run just fine for a little while at least.
I think you likely have several problems, might be related, might not. But best to try and address them individually at first. Since the charging system is important, and isn't directly tied into the engine management for proper function in terms of allowing the engine to run, and it is fairly simple, I'd go after that first.
Ok, so...
-Found an old post referencing the blue wire (exciter?) in that wire harness above the starter. No wires appear frayed or damaged.
-Cleaned up positive cable connections on battery.
-Took the alternator out and had it bench-tested at Advance. Got these results:

-Have not had any noise from the pulley or seizing. Stuck a screwdriver in the alternator blades and the pulley spins counter-clockwise but not clockwise.
-Removed the voltage regulator and it seems fine to me. The brushes seem to have enough "meat" on them:

-Could there be some other internal failure I'm not aware of. Since I bought the alternator the terminals have felt wiggly but GAP had assured me it was fine when they tighten down, which is true. It's never been an issue before. Pretty dumbfounded at this point.

Last edited by intro; October 10th, 2019 at 19:36.
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Old October 11th, 2019, 04:26   #22
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Looks to me like you need a new alternator.
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Old October 11th, 2019, 04:55   #23
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Looks to me like you need a new alternator.
The whole thing, yeah? I wonder why the warning light wasn't coming on? Confirmed the bulb is good. I guess I'll have to trace that wire all the way to the cluster. I think I'm just going to install some gauges, so I'll get to the bottom of it somehow.

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Old October 13th, 2019, 18:46   #24
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Looks to me like you need a new alternator.
New alternator in, charging again, still multiple misfires pending though. :/

I'm suspecting this is a vac leak so Ill try checking there next. Maybe replace the vac lines which have never been done.

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Old October 14th, 2019, 04:23   #25
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OK, so you got one problem fixed. Moving on to the next, if you suspect a lean misfire condition, I would use a scan tool and look at fuel trim (lambda). It should hover around 0 once the engine is warmed up some. Usually within about 5 minutes it should be in closed loop and lambda control.

There are hardly any vacuum lines on that engine. It is super simple. You can also watch the misfire counter with a scan tool to see which cylinders specifically are misfiring and when.
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Old October 14th, 2019, 07:10   #26
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OK, so you got one problem fixed. Moving on to the next, if you suspect a lean misfire condition, I would use a scan tool and look at fuel trim (lambda). It should hover around 0 once the engine is warmed up some. Usually within about 5 minutes it should be in closed loop and lambda control.
There are hardly any vacuum lines on that engine. It is super simple. You can also watch the misfire counter with a scan tool to see which cylinders specifically are misfiring and when.

Thanks. Yeah, I just realized there are not a lot. It looks like one was replaced on the left side. The other 2 over by the driver's side are still that corrugated style.

I'm going to need to get a VAG cable and the software, it's time.

This will seem like a stupid question, but I have the ignition wires going left to right 1-4 on the cylinder head and then according to the letter order on the coilpack. Does that sound right to you?

I'm also wondering if the NGK wires I picked up from Amazon warehouse were bad and thus returned. You can test wires for resistance right?

The misfire has gotten worse I think over the last 2 weeks. It used to be just p0302, now I'm getting P0300, p0302, p0304(P).

Anyway, I can only keep guessing so I'm ordering the Rosstech now.

Last edited by intro; October 14th, 2019 at 07:14.
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Old October 14th, 2019, 09:29   #27
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Ignition wires in the aftermarket, much like spark plugs, are often sold incorrectly for the 2.0L engines.

The AEG uses 06A-905-409-L, the AZG, AVH, BEV use 06A-905-409-N.

I would only use OEM type (Beru is usually a good brand) wire sets, and they really can only fit one way. They come already laced in such a way as to be pretty darn impossible to put on the coil incorrectly.
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Old October 14th, 2019, 15:57   #28
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...Double post

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Old October 14th, 2019, 17:24   #29
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Ignition wires in the aftermarket, much like spark plugs, are often sold incorrectly for the 2.0L engines.
The AEG uses 06A-905-409-L, the AZG, AVH, BEV use 06A-905-409-N.
I would only use OEM type (Beru is usually a good brand) wire sets, and they really can only fit one way. They come already laced in such a way as to be pretty darn impossible to put on the coil incorrectly.
It's funny, I went and checked out the Amazon page for the wires and now I'm seeing a whole bunch of reviews saying they caused misfires. I guess I only read one and didn't dig deep enough. I think you're onto something Oilhammer.
I went out hoping to try switching the wires 2 and 3 as some people said they arrived mislabeled and it affected performance (not clear on how the length would affect that). Didn't do anything but the question prompted me to check what I had in there before that worked just fine (NGK Part #: NGK 57021). The Amazon Part # is NGK RC-VWC039. I'm hopeful this will straighten me out but I do have my VCDS cable on the way just in case.

EDIT: NGK 57021 and VWC039 are the same thing. Damn!

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Old October 14th, 2019, 20:00   #30
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I'm going to hope that new wires will do the trick, but I will probably read the ohms on those NGK wires first, before ordering tomorrow. I'm sure the OEM wires at the dealership would be an arm and a leg.
One thing I continue to see, is the misfire gets better as the motor warms up. On cold start I will have 300, 302, and a (P)304. After warming up I can have the car revving, and only when the I ease off the gas do I start seeing the flashing CEL. I tried the poor man's version of VAG-com and scanned when I was revving the engine-No codes, as soon as I eased off I'd get P0302(P).

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