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High idle vacuum reading

G

gtiGreateness

Ready to race!
Hello all,

I have a P3 digital gauge, no Boost tap, plugged directly into the obd port. Vacuum during idle Usually reads between 19-21. However as of today idle is reading 9 PSI during idle. I know I have an exhaust leak, but this has been around for a month or two now. Just haven’t had a chance to look Into it yet.
Looking for help if this would cause the vacuum issue?

Thanks
 
Last edited:
vdubnick

vdubnick

Drag Racing Champion
did you have the AC on?

19-20 is normal with no AC, but it will drop once you turn on the AC

and no, exhaust leak will have no affect on idle vacuum
 
vdubnick

vdubnick

Drag Racing Champion
what does it go to if you coast in gear, foot off the throttle? if it doesnt go to 19-20 then you got an intake leak.... but if that was the case, you would probably notice a boost leak as well.
 
sterkrazzy

sterkrazzy

Autocross Champion
What's the motor sound like at idle? Are the rpms idling higher than normal or are they stable?
 
Last edited:
vdubnick

vdubnick

Drag Racing Champion
how many miles you got? could be cold start issues related to dirty intake... the lower vacuum is from the TB opening more to keep the engine running because something else isnt running smooth (clogged intake/fuel, etc)
 
G

gtiGreateness

Ready to race!
vdubnick said:
how many miles you got? could be cold start issues related to dirty intake... the lower vacuum is from the TB opening more to keep the engine running because something else isnt running smooth (clogged intake/fuel, etc)
Click to expand...
172k and climbing. I did romp on it a bit the other day, and thinking that may have caused it.
Letting it idle just allows it to settle at around 9.7 PSI.
know how to begin to diagnose the root cause?
 
G

gtiGreateness

Ready to race!
Scouring endless posts, followed some simple tests to check if I could find the source. Not PCV, replaced it with a spare I had. Could be DV, although I have a GFB DV, so unlikely. Haven’t noticed any immediate leaks. I guess boost leak test is next? Any body know a good easy DIY to test for boost leak?
 
vdubnick

vdubnick

Drag Racing Champion
gtiGreateness said:
Not exhaust possibly?
Click to expand...
i highly doubt it.

you have 172k? when was the last time you pulled the intake and cleaned valves? do you have any OBD scan tool? have you checked for misfires on cold start? if it runs rough when cold, it is likely the intake being dirty and/or clogged injectors or bad spark plugs.
 
G

gtiGreateness

Ready to race!
I replaced it all last year. I had a bad intake manifold, so did carbon cleaning at the same time with new spark plugs and coils. All was dandy afterwards until a few days ago :(.
 
G

gtiGreateness

Ready to race!
Scanned car, code came back as below


2 Faults Found:
008801 - Boost Pressure Control Valve (N249)
P2261 - 000 - Mechanical Malfunction - Intermittent
Freeze Frame:
Fault Status: 00100000
Fault Priority: 0
Fault Frequency: 254
Reset counter: 255
Mileage: 258216 km
Time Indication: 0
Date: 2043.14.24
Time: 20:02:54

008213 - Intake Manifold Flap Position Sensor (Bank 1)
P2015 - 000 - Implausible Signal - Intermittent
Freeze Frame:
Fault Status: 00100000
Fault Priority: 0
Fault Frequency: 1
Reset counter: 255
Mileage: 274687 km
Time Indication: 0
Date: 2053.14.27
Time: 15:44:04

P2015 is definitely new as this was cleared when I replaced the intake manifold last year.
 
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