GIAC chip: Pressure tested, changed DV, N75, and plugs and still having boost issues
Thread Starter
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GIAC chip: Pressure tested, changed DV, N75, and plugs and still having boost issues
Chipped my 2000 A4 1.8TQTip this past weekend.
Had immediate surging issues and was going into "safe" mode where boost is restricted.
Was getting 17964 Charge Pressure Control: Negative Deviation DTC.
Replaced DV, replaced stock N75C with new N75J, replaced OEM plugs with NGK BKR6E gapped to 0.030.
Car drives and boosts a lot better now after starting up fresh but still occasionally goes into safe mode if I am driving her hard on the highway.
Haven't had another chance to check for codes again - any thoughts?
David
Had immediate surging issues and was going into "safe" mode where boost is restricted.
Was getting 17964 Charge Pressure Control: Negative Deviation DTC.
Replaced DV, replaced stock N75C with new N75J, replaced OEM plugs with NGK BKR6E gapped to 0.030.
Car drives and boosts a lot better now after starting up fresh but still occasionally goes into safe mode if I am driving her hard on the highway.
Haven't had another chance to check for codes again - any thoughts?
David
Member
Joined: Aug 2000
Posts: 13,105
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Wait a minute.. negative deviation??
log block 115 w/ VAG COM. Pressure test car!
Check your L hose.. I hope you already had the factory one replaced! :-o Also check the vac hoses that go from your intake manifold to the N249, and the vac hose that goes from the N249 to the DV. These are common failure points. Especially the L hose on the 2001.
<img src="http://pictureposter.audiworld.com/8422/a4leak1.jpg">
Check your L hose.. I hope you already had the factory one replaced! :-o Also check the vac hoses that go from your intake manifold to the N249, and the vac hose that goes from the N249 to the DV. These are common failure points. Especially the L hose on the 2001.
<img src="http://pictureposter.audiworld.com/8422/a4leak1.jpg">
FAQ Author
Joined: Jan 2005
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mmart had a sensor that was given him grief. when i had the negative deviation dtc
it was my newly replaced DV that went south.
I never checked the DV as i had just replaced it and it turned out that the newly replaced DV was the cause. I didnt have a record either of when i installed it so between 1-3K miles and the thing went south on me.
<a href="https://forums.audiworld.com/a4/msgs/2349177.phtml"> The cause</a><ul><li><a href="https://forums.audiworld.com/a4/msgs/2337436.phtml">the problem 17964</a></li></ul>
I never checked the DV as i had just replaced it and it turned out that the newly replaced DV was the cause. I didnt have a record either of when i installed it so between 1-3K miles and the thing went south on me.
<a href="https://forums.audiworld.com/a4/msgs/2349177.phtml"> The cause</a><ul><li><a href="https://forums.audiworld.com/a4/msgs/2337436.phtml">the problem 17964</a></li></ul>
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negative deviation was before the n75j was installed
because it is when you are pushing it hard on the freeway that it goes into limp mode my guess would also be the n75j.
if you really want to upgrade your n75, i would recommend the latest stock part, the n75f.
throw back in your n75c or get an n75f.
if you really want to upgrade your n75, i would recommend the latest stock part, the n75f.
throw back in your n75c or get an n75f.
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Thread Starter
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OK - I will try stock N75 on Monday when I am back from a trip - MAP sensor ? inside
So based on what I have read in the archives, the car is going into limp mode when the MAP sensor detects pressure above some threshold.
Pressure is rising above the threshold as the N75J is allowing it to do so, resulting in "overboost". Sorry - still no VAG COM, so no codes. Changing back to the N75C/F will limit the boost pressure and the cars houldn't exceed the MAP limit and go limp.
What is setting this threshold? Can it be raised?
If I upgrade the turbo to K04 at some point, will I have this problem or will the appropriate N75 limit boost (and therefore the effectiveness of the new turbo)?
Pressure is rising above the threshold as the N75J is allowing it to do so, resulting in "overboost". Sorry - still no VAG COM, so no codes. Changing back to the N75C/F will limit the boost pressure and the cars houldn't exceed the MAP limit and go limp.
What is setting this threshold? Can it be raised?
If I upgrade the turbo to K04 at some point, will I have this problem or will the appropriate N75 limit boost (and therefore the effectiveness of the new turbo)?
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300mbar or 4.35psi difference between actual and requested
no you cannot change it. it's a safety measure of the ecu. im not sure if tuners can change it or not, but you def. can't.
when you get a k04 you need to get a new ecu tune designed for a k04 from giac.
when you get a k04 you need to get a new ecu tune designed for a k04 from giac.