Im having this code and problem... heres the symptoms

When i go WOT the car push hard as always but after some more WOT runs it doesnt build any more boost,the exhaust sound changes drastically and it barely hits 0.4..

I have changed the Diverter valves back to stock without luck..

Im pointing to change the N75 valve (Boost control Solenoid)..

what could be the problem? thanks

Codes stored on ECU are

p0234 Overboost


Mods are

AGP DV Valves
GIAC Tune
Evolution Motorsports Filters
IPD Plenum
Fabspeed Exhaust With bypass pipes
FVD Intercoolers

If the problem is the Boost Solenoid Im Planning on upgrading to the AGP Boost Control Solenoid..

please Help

 

I would look toward the BCS also. You may be able to take it apart and clean it out. Do you ever have boost oscillations or inconsistant boost? Also look around the engine bay for any damaged or broken vacuum hoses. Im also concerned with your GIAC tune. Was it tailored to work with the extra parts you put on, plenum, intercoolers, etc? Sometimes when you put extra parts that the tune is not designed for on, the computer cannot compensate for the extra flow fast enough so an overboost situation can occur.

 

thanks for the reply.. the tune was made for the mods I have.. Car was perfect till last week..Im putting 486 hp to the wheels, is there any way to clean the BCS?

Thing is I dont know why the problem starts after couple of WOT runs...

 

Could be the turbo getting super hot. I drove a tuned GT2 and after a few runs the boost wouldnt come anywhere near peak. There were no CELs though. My BCS on my WRX was able to be pulled apart and cleaned. On the Cayenne I am not sure whether or not it can be taken apart. I bet though at least you could just shoot non-chlorinated brake cleaner through the ports when its energized and not energized by taking some leads and hooking it up to the battery jumper post.

 

Did you find the cause of this?

 

Agree, GIAC tune is an overly-aggressive, generic mapping that is notorious for heat-soaking many turbo vehicles....

 

Would the BCS (at rear of engine, yes?) cause boost surging also? Mine sometimes sits at 0.4 bar, other times starting from first gear from dead stop, I can feel it surge with lots of power.. I get the same code. Stock otherwise.

 

Opening of the turbo waste gates is controlled by pressure in the lines to the wastegates.

Over boost can be caused by leaking / split wastegate lines or wastegate actuator diaphragms as either wastegate may not be opening when required, thereby putting the system in an over boost situation.

 

Waste gate, what would cause it to not get full boost unless I do a slow roll?

Or if I'm cruising on the highway and hold it in 4th gear for several seconds, then downshift to 3rd under full throttle, I get full boost and LOTS of power.. Thoughts? 125k miles and everything is stock/original except wear parts.

 

If the ECU senses an overboost condition and latches the overboost code, it will then limit the boost to a maximum of 0.4 bar until reset.