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VW MKIII-A3/B4 TDIs This is a discussion about MKIII-A3/MkIII Jetta/Golf (<99.5) and B4 Passats (96,97) TDI's. Non TDI related postings will be moved or removed.

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Old October 4th, 2005, 13:11   #16
GoFaster
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Default Re: How to troubleshoot low power on an A3/B4 engi

Quote:
"3j... Also perform the "official" MAF test: in third gear, while monitoring MAF using VAG-COM, floor the accelerator at 2200 rpm. It should show &gt;800 mg/stroke..."

Here's what happens with my car: I slam the pedal down on third and 2200 rpm. Car starts to accelerate and both specified and actual MAF go to 847,9. When it reaches 3000rpm actual value drops below the specified value. When I reach 4000rpm actual is about 730. Sometimes it may fluctuate a bit. During this rpm range (3000...+4000) accelaration is unsteady: First it pulls nicely, then it doesn't, then pulls again. Could it be the MAF? Boost pressure fluctuates also a bit but only about 0,1...0,15bars.
You are getting lower-than-specified measured air volume. The interpretation section lists several possible causes. How clogged is your intake manifold??
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Old October 5th, 2005, 10:33   #17
bennyvatten
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Default Re: How to troubleshoot low power on an A3/B4 engi

There's about 2...3mm thick deposit on the walls of the intake manifold. I haven't taken it out to clean it. I was able to check it out when I plugged the EGR. Clogging might be worse than it seems. Maybe I'll have to take it out and see...
BTW, does plugging the EGR affect the results in tests in step 3?
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Old October 7th, 2005, 14:51   #18
GoFaster
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Default Re: How to troubleshoot low power on an A3/B4 engi

A clogged intake manifold will mean that the engine can't breathe, which means it'll show less than specified air intake volume under load. The condition will be the worst when the engine is trying to breathe the most air, at high revs. If the situation gets bad enough, the discrepancy that the computer sees can cause "limp mode" ...

The diagnostic procedure explains when you should have the EGR connected and when you should disconnect it. The diagnostic procedure assumes that the vehicle is in stock form (i.e. EGR working), or close enough to stock that everything still works the way it did when stock. If you make changes to the vehicle, there's no way to account for that in a generic procedure (too many variables); you're on your own. If necessary, you can always go back to stock functionality and do the diagnostics from there.
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Old October 10th, 2005, 09:37   #19
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Default Re: How to troubleshoot low power on an A3/B4 engi

I worked on my car this weekend, replacing all the vacuum hose, per the above instructions. I've had a 0575 code for some time and was way low on power. Occasionaly, I would see a code for EGR intermittant as well. After replacing the hoses (the blue one to the wastegate was shot), I got a new code (1260, I think) which was N75 open to ground. I didn't have time to clean the N75, so I let it sit over night. The next day I cleared the codes and took the car for a ride. It definitely had more pep and the N75 code never came back. Boost is up to 1840 milibar now (was about 1300 before new hoses and ambient pressure at 1000 mb). I still had the EGR code. Later, I drove the car, but reset the codes again. The car drove even harder than before. A day later and no codes, yet!

I'm able to climb hills, which before the fix would slow me down from 60 to 50 mph. I not afraid to pull out into traffic now, knowing I can accelerate at a brisk pace. This forum sure has helped make my car more enjoyable.

Thanks,

Fran
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Old November 15th, 2005, 15:16   #20
Steve_McQ
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Default Power Loss/No Boost

I'm new to TDI's and new to the TDIClub. I sent a message to the group awhile back about the power loss problem that you posted your trouble-shooting suggestions for. I converted a 98 Jetta to run on vegy oil. About a month ago, a few months after running on oil, I lost power one day and it hasn't been back since. The power loss is a little different than your listed symptoms. I have no upper "zip" in any gear, 1-5. The car runs fine, and I can get it up to 75-80MPH on the highway, but I lose speed going up inclines, or I can't pick up speed trying to pass or go up inclines. The problem does not get better or become intermittent after turning the car on/off - nothing. I am getting the 0575 manufold pressure code on VAG-COM. Here's what I've done...

Cleaned the intake manifold (did this before problem)
Changed the timing belt and adjusted the fuel mixture (again, before the problem)
Changed the red/blue/black hoses coming off the N75 (they old ones were very clean, but I still changed them)
Changed the black hose from the pressure manifold to the ECU
Checked the small hose in the ECU housing - looked fine
Changed the diesel fuel filter
Applied 12Vdc to the N75 (clicked)
Applied 30PSI to the red hose while activating N75 via VAG-COM - the wastegate linkage went back and forth
Sprayed WD40 in the wastegate hose barb

From what I'm experiencing, it sounds like it could be a leak, since it just went away and has never come back, but I can't hear any pressurized air leaks - could it be on the low pressue side? I haven't checked any of the lines/hoses as you suggest. You have a lot of information there, I was hoping you could help me target the remaining things I should check knowing my specific symptoms.
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Old January 14th, 2006, 15:27   #21
onlyn8v
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Well, I tested my boost issue today and got this:
[IMG][/IMG]

This is under load in 3rd gear

So I read through this post and got 12-13 psi at red hose until it spike to 15 then limp mode

Then I connected to the blue position and got nothing- nothing then limp mode. The car feels normal then boom, limp mode.

So, Im guessing that the N75 is done? Thanks for the help!

[IMG][/IMG]



[IMG][/IMG]
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Old March 28th, 2006, 10:00   #22
MattBissell
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Just wanted to post for posterity. Fixed my intermittant limp by replacing the turbo. The wastegate actuator was full of oil and I was not able to get the oil out without pulling the turbo and pumping it out by actuating the wastegate lever manually. Had similar symptoms to onlyn8v above. Wastegate diaphram may have been faulty(leaking) as well.

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Old June 19th, 2006, 12:10   #23
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Default PDF of diagnosis guide...

I made myself a nice PDF version of the diagnosis guide, and would like to share it - is there a way to upload such things to the forum?

EDIT: Sorted it out (the pics server is for so much more than pics!)
http://pics.tdiclub.com/data/517/Lim...nosisGuide.pdf
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Old July 10th, 2006, 19:15   #24
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A friend & I just finished finding the problem on his B4 Passat. Hooked up Vagcom and it had the old "00575 Intake manifold pressure control difference - intermittent" code. Looked at measuring block 001, 003, 011. Found that boost would follow until the power dropped suddenly. Looked at the MAF readings and the actual was way lower than specified and it wouldn't get much above 500. We went to swap the MAF sensor, but found the problem was a partially plugged MAF screen on the inlet side of the MAF. Turns out that one of the clips on the air cleaner was missing allowing particles to get past the filter and and cause the blockage over time. Got a toothbrush and carefully brushed the debris away. Re-installed the MAF and low and behold the power was back. Cost $0.00.

Thought I would post this as this wasn't part of the "00575 Intake manifold pressure control difference - intermittent" code troubleshooting in section 2.
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Last edited by starrd; July 11th, 2006 at 07:20.
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Old July 28th, 2006, 19:01   #25
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Default 00575 code

I did all the checks and couldn't find any thing wrong . I read another post about snow screen. Yep mine was pluged completly . removed it and reset the ecm and car runs like new
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Last edited by beetle1963; August 12th, 2006 at 18:13.
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Old August 6th, 2006, 00:44   #26
jjsbiggs
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Thanks GoFaster for the excellent troubleshooting guide. My 98 Jetta TDI started dropping in to limp mode and would throw the 00575 code. I found that my N75 was not clicking and the boost would just climb until it hit limp mode. To verify I replaced the N75 valve with a T fitting connecting the black, blue and red lines (putting the turbo in give me less boost mode) and could then verify my waste gate was opening and dropping the boost back down with the pressure gage. I replaced the N75 valve this weekend before I took off for Maine and the car ran perfect with the requested pressure and actual tracking each other on VAG-COM. Once again thanks for all the help you guys provide.
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Old December 27th, 2006, 19:52   #27
Ashokan1
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Anyone have suggestions as to where to get replacement hoses for the blue and red hoses on the N75 valve? Size and lengths, etc?? Thanks.
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Old December 28th, 2006, 07:33   #28
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Quote:
Originally Posted by Ashokan1
Anyone have suggestions as to where to get replacement hoses for the blue and red hoses on the N75 valve? Size and lengths, etc?? Thanks.
Check the last post on this
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Old December 28th, 2006, 11:53   #29
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Just what I was looking for...Thanks.
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Old January 15th, 2007, 19:45   #30
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I'm not seeing any mention of the Turbo actuator "Pressure Unit", which is the pressurized diaphragm that actuates the turbo linkage. Mine hisses like a deflating balloon.
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