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Old 10-16-2017, 11:09 AM   #1
leforce
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Member#: 246246
Join Date: May 2010
Default Is my throttle body faulty?

Got a MY08 STi, the symptoms are:
slight hesitation at partial throttle at around 2000rpm.
Abnormal high load readings with rich AFR readings reaching 3.4 while max is boost is around 22psi only!
Excessively rich AFR readings all over, I had to increase the stock injector scaling since ECUflash won't go above 14.7 in the fuel table.
I know that high loads & rich AFR are usually associated with boost leaks, but I have checked for leaks twice & found nothing!
I noticed that the slight hesitation at 2000rpm can be eliminated by zeroing the AVCS tables in the corresponding rpm/load area, 2000rpm/0.30 load. I logged AVCS while revving the engine a bit & all numbers looked fine. I noticed that throttle % is never at 0 while idling, off throttle, it's always at around 2.7%. I logged requested torque & detected a gap between logged values & the actual table values. As an example in the area I'm experiencing the hesitation, 2000rpm @ 6% TPS, the value in the able is 15.4 while the logged value is around 22!
Could this mean that my throttler body is faulty? Would it explain the hesitation, high load, & rich AFR?
I'd appreciate your feedback
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Old 10-16-2017, 11:35 AM   #2
mrsaturn7085
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Member#: 375462
Join Date: Dec 2013
Chapter/Region: NWIC
Location: Portland, OR
Vehicle:
2006 Impreza WRX STI
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If you have a fault in the DBW system, it will throw a code - this system has nearly as many internal fault checks as the ABS or SRS system.
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Old 10-17-2017, 10:39 AM   #3
leforce
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Well, I have no codes, but still the logged requested torque is higher than corresponding values in the tables to the point that I'm hitting 22psi boost at all modes intelligent, sport, & sport sharp! My requested torque tables are all stock!
Any clue what might be causing that?
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Old 10-17-2017, 11:43 AM   #4
mrsaturn7085
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Member#: 375462
Join Date: Dec 2013
Chapter/Region: NWIC
Location: Portland, OR
Vehicle:
2006 Impreza WRX STI
WR Blue

Default

Your throttle is not faulty and your DBW controls idle - it will not match the table when idling as the closed loop idle control takes over. 2.7% is a reasonable throttle position for idling. There could also be some compensations happening, here.

I would focus on the boost control until you resolve the overboosting - it's not likely caused by the throttle control.
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Old 10-18-2017, 09:15 AM   #5
hondaeater69
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1998 RS

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have you considered the FPR mod?
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Old 10-19-2017, 06:37 AM   #6
leforce
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Quote:
Originally Posted by hondaeater69 View Post
have you considered the FPR mod?
No, since the car is stock turbo, stock injectors. I went ahead and tuned the car, eliminated low rpm hesitation by zeroing AVCS tables in one slot (2000/30) Had to increase injector scaling to 600 to keep rich AFR under control. I still hit high load numbers, so I had to rescale my tables up to 3.30. Now, I'm running 25psi, the car seems perfectly fine.
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