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Just bought an evo! having issues though...

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Old Jan 11, 2018, 02:50 PM   #1
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Just bought an evo! having issues though...

So the car has an AEM wideband and digital boost gauge. The car boosts to about 20psi (manual boost controller) just fine, and the gauge reads boost fine as well.
Problem is, my idle vacuum is anywhere from -8 to -4 inhg, and I'm running rich basically all over the place. anywhere from 12-13.5 idle and cruising, and 10 or below under boost. Already replaced front o2 sensor.

I did a boost leak test at roughly 26 psi and the only leaks I could find is the bov (it's a go fast bits deceptor bov, definitely an older model though) and the oil cap was leaking quite a lot of air, so much so that I had to hold it down to hear any other leaks.
Both leaks got really bad over 25psi, so I don't see any issues currently driving at 21.

Also, the car doesn't run like ****, which is weird with such a huge vacuum leak.

I already tried changing the power source for the gauges.

Is there a way to check vacuum on evoscan? I'm thinking maybe the gauges are bad.

Any ideas?
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Old Jan 11, 2018, 06:23 PM   #2
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compression and leak down test
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Old Jan 11, 2018, 06:41 PM   #3
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compression and leak down test
did a compression test when I bought it, all good there.
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Old Jan 11, 2018, 07:26 PM   #4
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What mods do you have other than the mbc and gauges? Does it have CAM’s ?
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Old Jan 11, 2018, 10:21 PM   #5
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Bad tune?
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Old Jan 12, 2018, 01:26 AM   #6
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did a compression test when I bought it, all good there.
what were the compression numbers?
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Old Jan 12, 2018, 02:40 AM   #7
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What mods do you have other than the mbc and gauges? Does it have CAMís ?
TBE, intake, upper and lower intercooler pipes, mishimoto radiator, no cams.
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Old Jan 12, 2018, 02:42 AM   #8
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what were the compression numbers?
~125 across the board. It's a 9, so I've read these numbers are normal.
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Old Jan 12, 2018, 05:54 PM   #9
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wonder if your TB butterfly is leaking badly?
maybe that why it doesnt have any vacuum and your boost leak check is pushing a ton of air in the motor.

or thinking more... (out loud)... maybe a IAC valve is faulty
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Old Jan 12, 2018, 06:01 PM   #10
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This sounds like a tune issue to me. Have the injectors been changed since you bought it?
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Old Jan 12, 2018, 06:20 PM   #11
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This sounds like a tune issue to me. Have the injectors been changed since you bought it?
Nope, I checked via ecuflash and compared to a stock rom, basically only things that were touched is the high octane fuel and ignition maps. Even loaded a stock (tephrav7) rom and still the same thing.
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Old Jan 12, 2018, 06:21 PM   #12
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wonder if your TB butterfly is leaking badly?
maybe that why it doesnt have any vacuum and your boost leak check is pushing a ton of air in the motor.

or thinking more... (out loud)... maybe a IAC valve is faulty
Would that cause rich cruising as well?
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Old Jan 12, 2018, 06:26 PM   #13
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Update, now it's saying 0 vacuum, unless I give it some gas it'll fluctuate between 0-4 inhg. I pulled the line off the sender unit and there was indeed vacuum. Thinking maybe it's a bad sender, but that still wouldn't explain the richness.
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Old Jan 12, 2018, 07:58 PM   #14
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Possibly a bad sender happens quite often with the aem gauges. You can hook up a mechanical gauge to verify. Can get a cheap one at harbor freight.

as for the rich condition large vac leaks, larger injectors are installed and not scaled right. If you still have Evap on the car possibly the canister is saturated with fuel.
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Old Jan 13, 2018, 03:16 AM   #15
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Possibly a bad sender happens quite often with the aem gauges. You can hook up a mechanical gauge to verify. Can get a cheap one at harbor freight.

as for the rich condition large vac leaks, larger injectors are installed and not scaled right. If you still have Evap on the car possibly the canister is saturated with fuel.
Would the car run like crap if there was that much of a vac leak?
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