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Old 01-06-2013, 01:16 AM   #1
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Default Diypnp / IAC valve failure

Finally figured out why my IAC was all over the place, setting that worked great one day, failed the next, horrid warm up control (3k) rpms untill it was really warm, regardless setting etc. the last few days it was nearly impossible to get it into CL idle, I would have to ride the brake in gear to get it down to 1200rpm, then ease in the clutch etc.

On the highway today the valve failed open, giving me a steady 80mph in 5th ( yay cruise control right?) anyways, clamped the line to the IAC ( which now gets sucked flat at idle) and ordered a new valve.

Curious, but, is there anything in the way that the MS controls the iac (pwm closed loop) that might damage the valve?

I'm not going to lie, using spark advance, and tweaking the fuel has the car idling great with the valve capped off ( ignition advance picks up AC loads with very little fluctuation.
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Old 01-06-2013, 09:05 AM   #2
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post your settings.
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Old 01-06-2013, 11:25 AM   #3
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I'm pretty sure the settings are out of wack as I was chasing a failing valve, but, when It was working ,

Valve open was 60, closed 23, min duty for pid was 19, P=20, I=50,D=0, valve closed rpm was 700, open 2200 rpm. Crank to run 6, pid times 2.

Pwm freq was 9, lower than that and I got the hum.

Car would idle at 700rpm with the valve disconnected. Overall I think I had pretty tame numbers, but last week the PID numbers were getting much larger to control idle... P was close to 50, I near 160 to catch the idle.

I'm guessing its just a 18yr old valve failing, but want to make sure that there isn't a setting that could burn out the new one.
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Old 01-06-2013, 11:38 AM   #4
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seems like a lot of I value.

was the diode installed on it? by R4 and R7 pullups
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Old 01-06-2013, 11:44 AM   #5
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Yes, the fly back diode was installed. The car has an mp62 on the hotside, so the larger I seemed to help it respond to idle droop appropriately.

As long as there isn't a "don't do this" that I missed, I'm not too worried. I'll prob. Add that freq. multiplier board though for better control.
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Old 01-06-2013, 12:25 PM   #6
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what year valve? unless nb, no need. and eventhenthe code is good enough to control it.
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