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2002 Sonata 2.4L GL A/T, 2007 Tucson 2.0L
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Discussion Starter · #1 · (Edited)
Hood Motor vehicle Gas Automotive exterior Engineering

In an effort to diagnose if I have engine problems, I connected a vacuum gauge up.

The gauge was connected with a 'T' fitting to where a red striped hose labeled "P" just past the throttle is connected (pictured).

My results:
<-> = constant fluctuation

-20<->18 at idle, normal op. Temp initally

-0->23->20<->18 after throttle snap

-After a few minutes of waiting, 20<->8

What's going on here?
 

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2002 Sonata 2.4L GL A/T, 2007 Tucson 2.0L
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Discussion Starter · #3 ·
What are you attempting to diagnose? Are there any trouble codes stored in the PCM?
No codes. Trying to see if I have a no code misfire happening at certain acceleration speeds.
 

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The red stripe vacuum hose is the port to the evap canister/valve. The valve is occasionally opening & closing, so the fluctuation you see is normal. The official diagnosis at this port is to hook up a gauge to the port only (without T piece and the rest of the EVAP sys connected) and read vacuum, just to determine if the port is clogged or not.
 

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2002 Sonata 2.4L GL A/T, 2007 Tucson 2.0L
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Discussion Starter · #5 ·
The red stripe vacuum hose is the port to the evap canister/valve. The valve is occasionally opening & closing, so the fluctuation you see is normal. The official diagnosis at this port is to hook up a gauge to the port only (without T piece and the rest of the EVAP sys connected) and read vacuum, just to determine if the port is clogged or not.
So you're saying the correct way to check vacuum is to plug my gauge directly into the 'P' port and just leave the striped hose disconnected?

If so, wouldn't I have to seal the striped hose somehow since the purge solenoid would start drawing in air?
 

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If so, wouldn't I have to seal the striped hose somehow since the purge solenoid would start drawing in air?
no. How should air be moving anywhere without a pressure difference (vacuum vs atmosphere in this case) causing it ?
The vaccum source (engine) is disconnected from the EVAP system. All there is left is solenoid, evap canister and fuel tank.
 

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2002 Sonata 2.4L GL A/T, 2007 Tucson 2.0L
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Discussion Starter · #7 ·
no. How should air be moving anywhere without a pressure difference (vacuum vs atmosphere in this case) causing it ?
The vaccum source (engine) is disconnected from the EVAP system. All there is left is solenoid, evap canister and fuel tank.
OK, I connected directly to the P port without a T fitting.
All values in inHg taken with engine fully warmed up:

-Steady needle movement at 20.5

-0->24->20.5 after throttle snap

-22 at 2500rpm

From my research, this seems normal, so I'll have to examine elsewhere.
 
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