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Interesting Idle Vacuum Correlations PART 2

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Old 08-28-2008, 02:07 AM
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Well, that didn't do it.
But now I have reason to read the electrical diagram for a minute before I go through the trouble of pulling the alternator belt.
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Old 08-28-2008, 02:20 AM
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sorry...

wow though... i've learned more in the last hour in the fsm than i have in weeks here....

i know how i'm gonna spend time in honduras
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Old 08-28-2008, 02:31 AM
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The FSM gives remarkable insight - if you have the patience.

I've read it like a novel.
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Old 08-28-2008, 01:01 PM
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Yeah - EVAP, MOP and JAB are all on valves, but the flow positively.
I blocked the EVAP entirely at one point, but that did nothing.
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Old 08-28-2008, 01:43 PM
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Y. Sry.
I txt w/ acro.

(Yeah. Sorry.
I speak in acronyms.)
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Old 08-28-2008, 01:51 PM
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That's for sure.
Actually, that is probably part of the problem here.
I haven't really been able to think linearly on this one - I get side-tracked.

I am going to go try running the car with the alternator wire disconnected and then the battery disconnected and see what happens.
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Old 08-28-2008, 01:57 PM
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Is it the Fourth of July already?
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Old 08-28-2008, 02:01 PM
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So, you want to celebrate by setting my car on fire?
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Old 08-28-2008, 02:06 PM
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take the tps off and crank the car and take a vacuum reading. if your vacuum is in the normal range then you have eliminated one system.
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Old 08-28-2008, 02:22 PM
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my car has a vacuum reading of 15hg at idle too so I will be paying attention to this thread.
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Old 08-28-2008, 02:50 PM
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Originally Posted by olddragger
take the tps off and crank the car and take a vacuum reading. if your vacuum is in the normal range then you have eliminated one system.
olddragger
TPS? Throttle Position Sensor?
We don't have one.
You mean disconnect the throttle completely? What will that do?
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Old 08-28-2008, 04:19 PM
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It might (I suppose in theory), except no one else that is running this setup has lowered idle vacuum.
Really, if the turbine was restricting exhaust flow at only 6 g/sec, the car would stop running at WOT before I got to 4000 RPM.
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Old 08-28-2008, 05:26 PM
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Originally Posted by shaunv74
Maybe take a step back and list all the things that affect idle vaccum and walk through them 1 by 1.

Intake leaks
Intake restrictions
air density
rotor sealing
AC load
Alternator load
water pump
oil pump
Idle RPM
What else?
I'm wondering about rotor sealing. Ultimately it is the movement of the rotors that is creating the vacuum. Iirc, the test for engine recall involved some type of vacuum measurement. It seemed curious at the time that it wasn't a compression test. I guess a seal might still be good for compression but have some wear that would show up as lower vacuum? I dunno how to verify. Throw some heavy premix at it? Intake ports with some carbon blockage? Seafoam time?
Last edited by Nubo; 08-28-2008 at 05:29 PM.
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Old 08-28-2008, 05:32 PM
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The motor read this way out-of-the box with only 47 miles on it.
I already did the OMP jacking to maximum (the Mazda check for compression/vacuum loss) and it made no difference.
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Old 08-28-2008, 05:43 PM
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throttle not closing right
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Old 08-28-2008, 07:00 PM
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Plus, the idle speed would go up.
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Old 08-28-2008, 07:32 PM
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Something sucks under your hood.
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Old 08-28-2008, 07:34 PM
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Originally Posted by Easy_E1
Something sucks under your hood.


Originally Posted by Charles R. Hill
That which is obvious need not be discussed, thus I didn't bother mentioning it.
But, I am Captain Obvious!
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Old 08-28-2008, 07:46 PM
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Originally Posted by MazdaManiac
But, I am Captain Obvious!

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Old 08-28-2008, 07:54 PM
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Old 08-29-2008, 12:58 AM
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Small hole in your wastegate actuator?? Solenoid?

Are your fuel trims normal at idle?

Something that transferred with 2 different engines right....

Did you figure out the High amperage draw?
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Old 08-29-2008, 01:18 AM
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WG actuator is cut off from its vacuum/boost source at idle by the solenoid.
The problem followed two motors.
I didn't discover where the draw was.
It started raining before I got a chance to play.
Fuel trims are rock-steady 0/0.
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Old 08-29-2008, 01:20 AM
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Brake booster??
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Old 08-29-2008, 01:26 AM
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Plugged it. No difference.
Same with EVAP, OMP and JAB.
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Old 08-29-2008, 02:10 AM
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Originally Posted by MazdaManiac
Fuel trims are rock-steady 0/0.
Okay, maybe Cpt. Obvious here, but...

Doesn't this suggest there is no leak, otherwise trim would be stepping in? If so...

You've sort of ruled out engine seals. New engine rules out port problem.

What's left?
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