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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

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 August 13th, 2018, 21:45   #1
Bmangdog
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Join Date: May 2018
Location: Medford
Default Engine swap, low power

Spun a rod bearing on my old motor and found a used motor complete with 88k on it and swapped it in. The original motor before it spun a bearing had a low power situation just like the new one I swapped in. New fuel filter. Air filter. Threw a low voltage maf code (p0102), cleared the code and unplugged the maf and it had little to no effect on power. Plugged maf back in and cel is staying off now. Turbo is almost brand new stock replacement with about 5k on it. Also swapped another n75 in and had no effect. Car is a 2003 golf 5spd.
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Old August 13th, 2018, 22:39   #2
WildChild80
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Location: Hampton Roads, VA
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Have you verified mechanical timing?
Are you certain you don't have any vacuum leaks
How much vacuum does your turbo actuator start to move
Does your vacuum pump pull enough vacuum, one of mine is sick and I'm being lazy and driving my other TDI at the moment.


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Old August 13th, 2018, 22:44   #3
Bmangdog
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Mechanical timing is spot on. After you mentioned the vacuum pump I notice that the barb on it is loose. Could it be loosing vacuum there?
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Old August 13th, 2018, 22:50   #4
WildChild80
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I'm actually reading another thread now about it, I googled alh vacuum pump and it is a thread about an intermittent brake issue and an occasional low boost issue

Also check the hard line at the nipple as I've seen them crack, I've shortened and heated it up a little and slid it back on

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Old August 14th, 2018, 06:42   #5
Bmangdog
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I’ll give that a look today after I get off work
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Old August 14th, 2018, 19:17   #6
wonneber
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Did you check the code at Ross-Tech.com?
http://wiki.ross-tech.com/wiki/index...6/P0102/000258
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Old August 15th, 2018, 08:32   #7
KrashDH
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Join Date: Dec 2013
Location: Washington
TDI(s): 2002 Golf
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Quote:
Originally Posted by WildChild80 View Post
I'm actually reading another thread now about it, I googled alh vacuum pump and it is a thread about an intermittent brake issue and an occasional low boost issue

Also check the hard line at the nipple as I've seen them crack, I've shortened and heated it up a little and slid it back on

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I had an issue that I just posted up a bit ago and did a writeup about it, wonder if this is the thread you've been reading?

http://forums.tdiclub.com/showthread.php?t=490188

Walks through my troubleshooting pain and the solution
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Old August 15th, 2018, 09:27   #8
WildChild80
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That was the thread I read, did your problem start very slowly and become more frequent? I've got an issue where about once a month it'll just not have brake boost but I haven't noticed anything turbo related yet

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Old August 15th, 2018, 09:36   #9
KrashDH
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Quote:
Originally Posted by WildChild80 View Post
That was the thread I read, did your problem start very slowly and become more frequent? I've got an issue where about once a month it'll just not have brake boost but I haven't noticed anything turbo related yet

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Yes it did start slowly. I first noticed something odd when at the end of the brake pedal stroke, there was an audible "click".

Brakes still worked fine, turbo worked fine.

Then it got worse, where in the morning when I went to start it with a foot on the brake, the pedal was hard. As soon as I started it up though, pedal went soft (like it should feel) and everything worked as normal. This lasted for a couple months like this. It was a sign vacuum was being lost overnight. Turbo worked fine though as the pump was putting out enough to fill the reservoir.

Then it started having the serious issues where I was getting the stiff pedal, and limp mode (no power). Brakes would come back for 2-4 strokes, turbo would come back a bit longer than the brakes. The turbo will always work a bit longer because that vac resevoir, if your pump can fill it, will provide vacuum to operate the N75 and N18 valves. The reservoir does not supply any vacuum for the booster. The booster is in direct line with the pump. Hence, if your pump starts having issues, the brakes will be your first sign, followed by turbo issues.

It was then I started that thread and employed pretty much all of the cheaper/free fixes until it led me to the worn out pump.

Last edited by KrashDH; August 15th, 2018 at 09:39.
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Old August 15th, 2018, 09:41   #10
WildChild80
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Am I wrong to think that the vacuum pump vents into the crank case? Does it move enough air to make a blow by issue worse? I had that idea this morning

And I did the brake pump test on my all stock time capsule and it certainly makes vacuum faster than the other car...

I've got a 2000 that's all stock that I call Hans and the modified 2001 is Frans...it's a joke with my wife...

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Old August 15th, 2018, 09:51   #11
KrashDH
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Quote:
Originally Posted by WildChild80 View Post
Am I wrong to think that the vacuum pump vents into the crank case? Does it move enough air to make a blow by issue worse? I had that idea this morning

And I did the brake pump test on my all stock time capsule and it certainly makes vacuum faster than the other car...

I've got a 2000 that's all stock that I call Hans and the modified 2001 is Frans...it's a joke with my wife...

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The key check for the vac pump is hooking the mighty vac up to a known good pump, and then to the one in question, which is what I did.

My pump seriously took about 35 seconds+ to build any type of vacuum, directly at the nipple.

My buddy pulled vac at the hard line check valve from the brake booster to the pump, which almost built 22-25 hg vac instantly (maybe 3-4 seconds). Which would mean it's pulling full vac of the system that fast, including the brake booster volume.

If I couldn't even pull that value in 35 sec at the pump nipple, and he was getting full vac within seconds at that check valve, then there was no way that my pump would be able to provide vac for the volume of the booster let alone the system.

That check was done after I had peened ant RTV'd the nipple seal, didn't help my situation. My pump internals were worn.
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Old August 15th, 2018, 10:14   #12
BobnOH
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Join Date: May 2004
Location: central Ohio
Fuel Economy: 50/45/35
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Is this an ALH or are you over the seas as they say.
Guess we'll disregard the engine swap, this issue is the controls.
Use the low power diagnosis flow versus guessing. Code P0102 gives clues.
Barb on vacuum pump does move, but it shouldn't leak. Actuator on turbo are suspect at this age.
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Old August 15th, 2018, 10:39   #13
WildChild80
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I need to grab a mighty vac and get this test done...I've got a few pumps laying around and I may try one of those before I pony up for a new one

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Old August 15th, 2018, 16:11   #14
Bmangdog
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Checked turbo actuator and it’s all good, I didn clean my maf with some maf spray and WOW. I bet i picked up at least 20hp. There is still something holding it back a little. I’m thinking it might me a map sensor because my old motor and inter Oiler had bad oil buildup. I’m thinking a covered in oil MAP?
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Old August 16th, 2018, 14:26   #15
WildChild80
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Good luck getting the screws out, the only one I tried to get out, the screws rusted almost all the way through and as soon as I put torque on them they both snapped off, didn't care too much since I was changing it and the map anyway

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