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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 10th, 2018, 20:57   #1
arkworks
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Location: minnesota, usa
Default My Limp

Also known as "What's going on?" (by Marvin Gaye)
2005 GLS Golf BEW 145,000 Turbo replaced with a K** turbo by VW at 88,521 miles because the original "came apart".
Limp mode comes on if I push it too hard. Boost returns after cycling the key.
I have done the following:
Replaced vacuum lines, peened and RTV silicone to the wobbly vacuum pump outlet nipple resulting in Vacuum now at 23+ .

Measuring Block Graphs: ? how to post these? as a JPG?
011 TURBO

003 EGR

VCDS Output tests:
N75: Actuator arm moves smoothly 1 inch BUT while N75 is cycling 4.8% to 95.6% there is NO CHANGE in boost pressure, isn't this supposed to increase?
EGR test: cycles 250 to 400/stroke


VCDS Basic Settings:
N75 Boost pressure = no change
EGR - off = 370 on = 250/stroke

My questions:
1. The vacuum system holds vacuum for several minutes after I shut down BUT ONLY IF I remove and plug the vac hose to the EGR valve. If I leave the EGR valve attached the vacuum is gone within a minute. Isn't the EGR valve supposed to hold vacuum ? While running the system holds vacuum at 23 with everything attached.
2. From graphs above, the turbo always stops boost at about 80% of requested and the EGR is always over what is requested, what does that indicate?
3. Smoke test at 15 PSI showed: leaking intercooler connector hose which was replaced, re-smoked and no leaks but no change in actual boost.
4. SO, I disconnected vacuum to the EGR valve and engine is now much perkier, boost starts at about 2000rpm and holds to 4000rpm and no codes. I repeated the Output EGR test with the results of 420mm @ 0.8% and 220mm @ 85.7% even though it's vacuum line is disconnected !!? How is the EGR still working??
Measuring block 011 shows actual boost is barely 1000 when 2040 specified even though performance is better??
What's going on?

Last edited by arkworks; October 10th, 2018 at 21:40. Reason: graphs came through as a bazillion characters
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Old October 11th, 2018, 04:15   #2
gforce1108
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Fuel Economy: Jetta: 44.5 summer / 47 on snows
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Which EGR vacuum line did you remove? The EGR is electronic, and so is the "flapper" at the intake boost connection. There are 2 vacuum controlled valves - one for the 4 port runners and the other at the cooler (IIRC).
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04 Jetta GLS 5sp - EGR delete, RC3, VNT17/22, 3" turbo back exhaust & 2.5" FMIC+PD150 intake. SBC Stage 2 Endurance w/SMF. Eibach lowering springs
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Old October 11th, 2018, 06:40   #3
arkworks
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OK
I thought the electrical connectors were to position sensors.
I blocked the vacuum line to the EGR cooler valve. The other two valves I have are the N75 turbo boost and a third which goes to Manifold pressure which I thought was the anti shudder/run away stop flap. I don't know what the 4 ports are you mention.
Jim
Any idea how to post graphs as well?
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Old October 11th, 2018, 08:21   #4
gforce1108
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The 4 ports in the intake manifold where they connect to the head have additional flaps. I googled for someone's image:

From what I understand, the large flap (looks like ASV) gets partially closed (electronically), to increase EGR flow. The 4 flappers help with mixing, swirling or something else that helps with emissions.
Here is a link to my google drive with a breakdown of the vacuum system:
https://drive.google.com/file/d/1QUR...ew?usp=sharing
The N75 obviously needs to be left alone - the remaining control valve goes to the 4 ports mentioned above. I am pretty confident that you have a bad valve on the cooler - it should hold vacuum. The limp mode troubleshooting procedure, although mostly written for an ALH, does cover capping off EGR vacuum points that only open while driving.
I'm not an advocate of deleting EGR components until something fails - then I suggest ripping it all off (dynamic EGR would be nice if everything works). FYI - those little flappers have been known to fall off and get ingested into the motor - not good....
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Old October 11th, 2018, 12:21   #5
arkworks
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Wow, thank you. There is so much more there than I had seen. I will start with a replacement of the N18 EGR cooler valve and see where it goes next. I love the car and now remember how zippy it was at low RPM. I'd like that back.
Jim
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Old October 11th, 2018, 12:48   #6
gforce1108
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Quote:
Originally Posted by arkworks View Post
Wow, thank you. There is so much more there than I had seen. I will start with a replacement of the N18 EGR cooler valve and see where it goes next. I love the car and now remember how zippy it was at low RPM. I'd like that back.
Jim
I learned it all the hard way - there wasn't much info when I bought my BEW back in 06. I had researched for years planning to buy a TDI and ended up with an engine I knew nothing about! Shortly after I purchased mine there was a recall on the cooler. The dealer screwed up the recall by skipping the installation of several brackets and the alignment process and a flex line failed. I blanked it off and slowly removed the whole system. It's slow to warm up in the winter even with a new thermostat and that seem to be common once the cooler is removed (exhaust heats the coolant). The dynamic EGR I mentioned earlier is a tune that retains the hardware, but only uses it during warmup.
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