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Crazy vacuum leak. Help appreciated

9K views 30 replies 4 participants last post by  MainFrame 
#1 ·
I tried meticulously to sort this out thru research and fiddling on the car but i just need help.

I bought an 02 wrx about 6 months ago as a project. (not knowing much at all about subarus)
Car has
-565cc DW injectors
-intake
-tbe
-silicone tubro inlet
-fmic
-bov
-uncatted up pipe
car has 125k, was giving off codes for maf(found MAF unplugged) and front 02 so i replaced both, but the car still idles funny with MAF plugged in. now monitoring a/f ratios on my AP i notice 25% correction.. showing -8 psi vacuum at idle, when i revv and release throttle it nearly stalls finding idle again(this gets worse when engine is warm). Runs great other than the weird idle. Holds boost well. no codes anymore.. i believe i may have a vacuum leak but can't find it. going to build a tester when i have time and clean iacv. any input would be appreciated.. this car has a lot of potential and is my first subaru, please help
 
#3 ·
i can't tell the brand.. looks about the same diameters as spt or cobb.
just odd that it ran better with MAF unplugged before i started replacing sensors.
or maybe it was running lean the entire time
i will post a pic of the intake as soon as i can thank you for the reply
 
#6 ·
i did some digging around and found a black tube not connected to anything but cannot for the life of my figure out where it goes. in the picture(sideways picture) the tube is connected to this black sensor.. with silver clamp on it.. i found this hose on the driver side behind the manifold..... anyone have an idea what it is or where it could go?
i have a feeling this could contribute to the issue
 
#12 ·
It would throw things off.. but not near as bad as installing the injectors, or intake without a tune. All of those mods require a custom tune to run right.. and the BOV, well it just won't run right regardless of the tune.. unless you switch to speed density or blow through, and you're far from needing that.
 
#13 ·
well i was informed that it has been tuned for everything except the fmic (possibly bov)
i have suspicion that the guy before ran a bigger turbo and maybe replaced it with the td04 then pulled MAF to make it run stock ratios in limp mode to sell it (all without tuning or tweaking)
does this sound crazy? is it possible? i know he ran a blouch 16g at one point...
 
#15 ·
would doing so cause said symptoms?
The near stall after releasing of throttle (once engine is warm)
extreme low and high air fuel correction rates -/+ 25%
car drives fine pulls hard and hits full boost which is set to 16psi or so.
Or do i just have a leak i can't find?
Maybe just needs a tune really bad?
 
#16 ·
A boost leak test should let you know if there are any leaks.


Is your IAM at 16? Any feed back knock correction? It could be a number of things, but if there isn't anything obviously wrong mechanically, and you don't know what tune is on the car, I would suspect a bad tune.
 
#20 ·
I'd use an Open Port 2.0 (aka Tactrix) cable to pull the stock map off your car. Send it to an e-tuner along with a list of the mods on the car and pay them to investigate your tune in order to see if anything looks wayyy off. Or you could post your map here - lot's of knowledgeable folks who might be able to help you out.

Of course - if you've got a massive vacuum leak then fix that first. Get a boost leak test or do it your self by following the instructions here:
http://www.clubwrx.net/forums/gener...s/134312620-boost-leak-test-instructions.html
 
#21 ·
thanks for your reply.i am using an access port to manage it all right now. i recorded some data logs that are being inspected as we speak. i would post them here but am working on getting a program to properly display the info as well. Also in the process of building a boost leak tester. Same group that is looking at my logs i plan to get a proper e tune from as well "IA performance".. Stephen has been helping me and working with me a lot.. if anyone else would want to take a swing at it id love to email the logs to anyone willing to help. only big problem is now the idling issue is gone(which is fine) but now today while doing the 3rd gear pulls to log it started over boosting to extremely high numbers and it scared me so the car stays parked. investigating this as well
 
#25 ·
awesome thank you.
well i have performed the procedures for data logging i was given by IA performance i am going to post some links if anyone wants to take a swing at them.
thanks for your help
Oh and i performed a succesful boost leak test at home and fixed to leaks. didn't change driving behavior very much but slightly...
held boost like a champ.
 
#28 ·
to add an update to this, i am in the process of an e tune to know my engine management is proper but the vacuum is still low at idle and wanders pretty badly. I have performed multilple boost leak tests. fixing a couple small leaks but evreything is tight now. What else could cause this low vacuum -(7psi) at idle?
when i perform my test i plug everything connected to my turbo inlet. Does that leave anything other possible places for a boost leak?
 
#29 ·
Vacuum is supposed to be sub-atmospheric at idle since air is being "sucked" into the engine via scavenging as opposed to forced in under pressure due to the turbo. That being said, -7 is not low enough... I'd expect between -8.5 to -10.5psi. So you might still have a small leak.
 
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