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Old 01-18-2007, 03:40 AM   #1
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Default Idle/PCV question on a turbo '99

I've got a '99 10AE with a FMII kit (circa 2001). I just finished installing an Autronic SM4 engine management system.

It previously had a TEC2 which had such a large minimum fuel delivery that I had to idle at 1000RPM anyway.

The SM4 runs sequential so I can deliver half the fuel and can operate the idle control motor too. But I found that I couldn't get the idle any lower than around 950.

I can't find any vac leaks, the throttle butterfly is as closed as I can get it without sticking, the Idle screw is all the way in, and even with the idle control motor at 0% it won't go below 950 even with 0 advance at idle.

However, if I disconnect and plug the PCV hose, it'll go all the way down to 700

Do I need a restrictor in the PCV hose or is there something else I'm missing?
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Old 01-18-2007, 09:38 AM   #2
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Does it not run off MAP?
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Old 01-18-2007, 12:24 PM   #3
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Yes, MAP and intake manifold temp (speed density).
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Old 01-18-2007, 12:24 PM   #4
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pulling the PCV line must screw with the MAP reading.
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Old 01-18-2007, 12:35 PM   #5
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The only way to screw with the MAP reading is to let more air into the manifold. The mixture is perfect so it's REAL air getting in.

It appears that when there is vac in the intake, it's pulling fresh air from the drivers side of the valve cover, through the motor, and out the PCV valve into the intake manifold. Which is what a PCV system is supposed to do.

However it appears that it's either passing too much air, or there's something I'm missing that's supposed to compensate for it.
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Old 01-18-2007, 12:45 PM   #6
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my thoughts were more along the lines of the vacuum line to the map sensor being altered. However if not the case, then I'd go with programming or overall fuel pressure or something.
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Old 01-18-2007, 01:45 PM   #7
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A MAP/Programming issue would show up as an problem with fueling or ignition timing. Mixture has been confirmed with the on-board wideband and timing has been confirmed with a timing light. I have also removed the idle control motor and made sure that it had full range of motion on command from the SM4. The fuel system on a '99 is returnless and runs a constant 60psi at all manifold pressures. The fuel pressure has also been checked.

Can somebody check to see how much their idle drops when they plug the PCV hose?
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