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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 May 7th, 2017, 18:24   #16
edjet
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I had a friend at work that had an ALH with the same issue. He sold the car to a VW mechanic who found a lifter that was cracked on the inside around the valve mating pocket. The lifter would loose its oil prime when static and the engine would go through a short period of rough running until it built up its pressure enough to run smoothly.
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Old May 7th, 2017, 18:33   #17
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edjet, that's interesting! I wonder, though, how long it would take for a lifter to bleed down. Seems like it might not take that long: in the case of the daughter's car it takes quite a while of it sitting before it exhibits this issue: seems that the engine is always good and cold before it does this.
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Old May 7th, 2017, 19:03   #18
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I just recalled that I'd replaced a section of the return fuel line between the #3 and #4 injectors due to fuel leaking.

For some reason I wanted to take a quick peek under the hood before she drove off and that's when I saw that there was a significant fuel leak happening. I cut and installed a new piece but did not have any time to observe if it made any difference.

This was my bad in that I'd swapped out the injectors last summer and apparently cut that line a bit short. I do not recall there being any leaking prior to me spotting this recently. And interesting is that a shop up North has had their eyes on this car a couple of times and they didn't catch this (and they were aware of the cold start issue).

I don't think that I can get a reliable description from the daughter on how things are going. I hope to see the car in a couple of weeks.

So... could bad return lines do something like this?

Could it be that the IP really is sucking in air, that the injectors have a good enough supply of fuel for the engine to fire immediately but then air come in from the IP and it starts chugging? I'm still thinking that this is a bit temperature related though. NOTE: car has solid fuel lines- I cannot see if there are any bubbles- I REALLY need to do something about this (why Oh why were any of these engines rolled out without clear lines?).
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Old May 7th, 2017, 20:08   #19
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Another item for thought...

I installed injectors from a manual transmission car. I had known that the nozzles were different sizes between the autos and the manuals, but I wasn't aware that the autos' injectors operate at a higher pressure. Could this fact be in play here?

I just cannot recall how the car was starting before I swapped the injectors. I'm wanting to say that there was an issue and that I was hoping that the swap might help out: I have more exposure to the injectors that I swapped in because they came out of the wife's Golf: I figured they were good whereas I couldn't really speak to the condition the originals from the wagon.

From the TDI FACT page this is what got me thinking on this:
One of the improvements made on the A4 engines compared to previous models involved the increased fuel injection pressure from the injection pump with optimization of the fuel injectors. Manual transmission A4 TDI's have 800 bar (11,760 PSI) pump side pressure with 1100 bar (16,170 PSI) injection nozzle pressure. Automatic transmission A4 engines have 950 bar (13,965 PSI) pump side pressure with 1350 bar (19,845 PSI) injection nozzle pressure. To achieve this increase in pump and injection nozzle output pressures in the automatic transmission engines, the single injection pump plunger on the BOSCH pump was changed from 10mm to 11mm. This was required for emission purposes allowing the automatic version to inject the required quantity in the very limited time available at higher pressure, with a resulting 20% reduction in particulate emissions.

Pete, you out there?
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Old May 11th, 2017, 19:53   #20
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After pursuing the injector issue it's looking like this isn't the source of the problem, though it's possible that the added fueling could be amplifying it.

Kind of leaves one of three possibilities:

1) Weak lifters;
2) Bad compression ring;
3) IP leaking (air incursion).

#3 seems like a "duh," but the car never struggles to start. From all I've ever heard this kind of issue is going to cause hard starting. But, I'm curious, can it be that an IP could be just taking in a little bit of air and that the injectors, following shutdown, are still maintaining enough fuel (right at the front of the lines) such that the engine gleefully kicks right off, but then its next gulp contains a slug of air? This all clears up within a minute or so. Because this car doesn't have a clear fuel line on it it makes this really hard to diagnose. I would really like to get one on this thing: if this was my car, readily available, it would already be done!

#2 is plausible, but I'm wondering how this could be proved/disproved. Only way that I think possible would be with a cold compression test? Any chance I could have a stuck compression ring? I think I've only heard of stuck oil rings. And I'd already done a warm compression test and it produced very good numbers.

#1 seems like a perfect match as logic goes. This, and #2, however, seem to be pretty rare. Other than edjet's mention of it I see no other instances.
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Old May 11th, 2017, 20:46   #21
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For #1, do the lifters rattle a bit when cold? A lot when cold? When they stop does that coincide with the idle smoothing out?

My '03 rattles for a few seconds on a cold start... but no problems with the idle.
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Old May 11th, 2017, 21:03   #22
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A HUGE problem for me is that I've only ever seen this car a handful of times, and exposure to the cold starting issue perhaps twice. I can't say for certain whether there's anything out of the usual as far as rattling goes; it's hard to tell because one gets really distracted by the bucking. I'm inclined to say that I don't really hear anything out of the ordinary.

This is just one of those things that's made tough due to it being hard to get many testing cycles on, seeing as the car needs to be cold.

I really appreciate all the input here. When I'm able to see the car next and I'm able to get access to it when it's cold I'm going to take a video. I doubt that I'll be able to put any wrenches on it (really, we're talking Mothers Day!): the car's 01m has signaled that it's heck-bent on starting on a death march- if I act on it now (well, I'm probably going to have someone up North act on it) then it might be saved for a few more kms/miles, long enough for me to sort out this cold start issue.

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Old May 25th, 2017, 10:53   #23
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I'm having an extremely similar issue. The car starts right up every time, then idles rough until it's warm with some smoke. Hope you can figure out what's going on!
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Old December 13th, 2017, 04:02   #24
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I have the same issue on my wife's beetle I just put together for her. Anybody solve this yet?
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Old December 13th, 2017, 04:06   #25
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Unfortunately I've had no further delvings.
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Old December 14th, 2017, 18:26   #26
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I extended the GP time on my wife's and it solved her cold start. Mark, how is it now, I added aprox 6 more secs to it.
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Old December 14th, 2017, 19:26   #27
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Simon, I haven't heard a word (was hoping to hear a bit from you). Does the GP time govern only the "wait to start" time, or does it [also] extend the after-glow? And this now brings up yet another question: could it be that the after-glow (post start) glow time is messed up?

Can't help but think that a correct battery could help: really irks me that a battery place couldn't install the CORRECT battery!

This is just a weird issue in that issues almost always impact initial start. I'd figure that everyone would like a car that starts this easily.
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Old December 14th, 2017, 20:39   #28
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Quote:
Originally Posted by UhOh View Post
Simon, I haven't heard a word (was hoping to hear a bit from you). Does the GP time govern only the "wait to start" time, or does it [also] extend the after-glow? And this now brings up yet another question: could it be that the after-glow (post start) glow time is messed up?

Can't help but think that a correct battery could help: really irks me that a battery place couldn't install the CORRECT battery!

This is just a weird issue in that issues almost always impact initial start. I'd figure that everyone would like a car that starts this easily.
Not sure about after burn but they stay on longer so they get really hot, which is better for cold starts.

I know, not a fan of that battery company. Hopefully they sorted it out.

I'll email you later, just doing paperwork,
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Old December 14th, 2017, 21:57   #29
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I managed to find out the answer to my question about GP after-glow. All the information one would want to slurp up can be had here;

http://forums.tdiclub.com/showthread.php?t=123304

In a nutshell: after-glow is roughly 2x the time of pre-glow. Adapting GP settings results in shifting the temperature off-sets rather than altering time: if one increases the temperature offset then GP glow will occur at warmer temperatures; at lower temps they'll glow longer.

Seeing as when the engine warms up (doesn't take long to get to a point where it's smooth) one could expect that shifting the GP value upwards would result in a longer duration of after-glow, which would help with early, cold combustion.

Better vetting of GPs is probably also something to consider. That thread notes that even with good resistance values GPs may not glow as hot as they are supposed to.
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Old December 16th, 2017, 17:43   #30
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compression test? I bet she runs a crap load of 100% biodiesel thru it to keep you outside working on the car
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