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Old 06-24-2004, 03:36 AM   #1
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Default Timing cut?

I've had this little problem for a while. Moderate, steady acceleration, shift into third. It seems fine for a second, then the rpms drop a little, engine tone changes, and A/F gauge goes a little more rich. If I keep the pedal where it is, it sets a code for the BCS (which I have bypassed) after a few seconds.

It does not happen under heavy throttle, not that I can feel anyway, but the BCS code frequently comes on under heavy, high speed acceleration.

Is this the PCM cutting timing because it can't dump boost? That'* what it seems like to me.
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Old 06-24-2004, 04:49 AM   #2
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Your diagnosis is correct. I grabbed this for ya.
Quote:
Under most conditions, the PCM commands the boost control solenoid to operate at a 100 percent duty cycle (ON) to allow full boost pressure upon demand. However, if reverse gear is selected or the PCM detects rapid deceleration or engine load is extremely high, reduced boost pressure is desired. Under these conditions, the PCM commands the boost control solenoid to operate at a 0 percent duty cycle (OFF), which opens the bypass valve. With the Bypass valve open, boost pressure is reduced by recirculating intake air back through the supercharger inlet
I further went on to read that if the PCM cannot curb boost that the timming and fuel will be cut back to protect the motor.
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Old 06-24-2004, 12:57 PM   #3
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Well ok then. Thanks.
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Old 06-25-2004, 01:46 AM   #4
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Quote:
I further went on to read that if the PCM cannot curb boost that the timming and fuel will be cut back to protect the motor.
Now if I could just convince DHP about that......
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Old 06-25-2004, 03:33 AM   #5
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Should I get a vid of my tach and A/F gauge for them?
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Old 06-25-2004, 11:08 AM   #6
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John, the Jet Stage 2 should work in your car, and is supposed to delete the overboost protection. I assume it works, as I didn't have to bypass my BCS.
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Old 06-26-2004, 02:07 AM   #7
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Interesting. I've given that thought before, shot Jet an email and they said their 93 chip wouldn't work in a 92 because the computers are programmed differently, but didn't tell me what the difference was. A 93 has 5 lb-ft more torque, right? I've also considered getting a 93 PCM and swapping, then getting a Jet, but wasn't sure if it all would work. What do you think about that?
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Old 06-27-2004, 03:55 AM   #8
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Hmm, I put the BCS vac line back to normal to see what would happen. Timing retard is lessened, but still there. And I still get the BCS code. Did I ruin my BCS having it disabled for so long?
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Old 06-27-2004, 12:21 PM   #9
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You're still getting full boost, and it'* as quick to respond on the gauge as normal?
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Old 06-27-2004, 10:52 PM   #10
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It may need to cleaned up and lubed if its been held for too long?
Can you maunally move it in and out?
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