# Not Boosting after 1st gear



## Pezis (Jan 18, 2010)

Ive had this problem since I recently bought the Car, its a 2000 S4 with 110k miles on it and newer turbos and the timing belt done. When flooring it from a dead stop the boost peaks to 9 and then drops to 0 once Im in second, and stays at 0 while floored. Im guessing Im looking at a boost leak? Also I got the gauge that goes below 0psi I am not understanding how it goes below. I also have a little tint of blue in my exhaust some times. Any help is greatly appreciated thanks.


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## RJ-18 (Mar 29, 2007)

*Re: Not Boosting after 1st gear (Pezis)*

0 PSi??? Hmm... U sure 0?? 
Possibly the car is on Limp Mode.. This happens when the ECU finds a problem in your motor and trying to protect your motor.. The ECU would cut your boost instantly..
Try scanning it with VAG-COM..
Log Block 115. 
If ur not familiar with it, stop by at SHUCKS or Autozone, borrow a UNIVERSAL OBD-2 Scanner, see what codes the ECU is throwing! --WRITE EVERYTHING DOWN-- then clear all the codes..
See if your boost is back after the DTCs are cleared up.. If it's back, then it was in limp mode.. Drive it on the freeway Wide Open Throttle for a bit. If the the boost is gone again (limp mode again), you may have a N75 problem or wastegate.









Hopefully this helps!! Let me know...


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## Pezis (Jan 18, 2010)

*Re: Not Boosting after 1st gear (RJ-18)*

P1606 Rough Road Spec. Engine Torque ABS-SG - Electrical Malfunction A
P0455 Evaporative Emission Control System Leak Detected (large leak)
P1176 O2 Correction Behind Catalyst,B1 Limit Attained
P1177 O2 Correction Behind Catalyst,B2 Limit Attained
P1296 Cooling System Malfunction 17704
P0741 Torque Converter Clutch Circ Performance or Stuck Off 
All the codes that came up, So the motor would boost in 1st gear and because of that it would read a fault and not boost in any other gear? If it tossed an error wouldnt it not allow me to boost in 1st eaither?


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## ryanjn (Mar 3, 2009)

*Re: Not Boosting after 1st gear (Pezis)*

I had a very similar experience with my A6, 2.7t. The problem turned out to be that both my wastegate actuators had failed (the diaphragms), and were not opening the wastegates once the requested boost was met. This would result in an overboost, and the ECU would throw me into "limp mode". I'd suggest finding someone local with VagCom to check for non-generic codes to see if you're throwing something similar. If you can't, and have a reliable tuning shop, have them vacuum test your actuators by applying pressure to the host from the diverter valves. 
I was fortunate to find a shop willing to replace just the actuators and NOT the turbos, but the entire engine had to come out to do so.. and that cost a pretty penny in labor.


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## GLS-S4 (Jun 6, 2005)

*Re: Not Boosting after 1st gear (ryanjn)*


_Quote, originally posted by *ryanjn* »_...have them vacuum test your actuators by applying pressure to the host from the diverter valves.

If you want to test wastegate actuators, you want to apply low and controlled pressure to the line that T's off the bottom of the N75 valve.


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## julex (Jan 24, 2009)

Sounds like some hoses are torn and perhaps some wires too. It seems like your car cannot trad the temperature right, some electrical problem there too. Get Vag-Com and P codes tell pretty much nothing anyway.


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## Pezis (Jan 18, 2010)

*Re: Not Boosting after 1st gear (Pezis)*

Update---- 
So Ive been having this problem I believe since I got the car. In 
1st,2nd and 3rd when I floor it it will peak boost to ~8psi and then drop to the 0-1psi mark. I have a code on the TC wondering if that is the problem that it is putting it into limp mode. When I cleared the code it would boost 1st peaking at 8 and dropping to 5 then peak at 8 when shifted into second and go back down to 5 but after I shifted into 3rd it would go to the 0-1psi mark. Also if I repertively hit the gas like a retard, it will stay at 5-6psi boost like it is suppose to in gears 1-4. Hopefully this is limp mode problem if not I was reading and possibly wastegate problem? And help is appreciated.


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## GLS-S4 (Jun 6, 2005)

*Re: Not Boosting after 1st gear (Pezis)*

Fix some of the easier DTC's.
Low pressure test (~5-8psi) the Intake System to check for intake leaks.


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