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Old 06-21-2013, 07:12 PM   #1
Masterchief117
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Question Help, stage 3 wrx randomly losing vacuum and shutting off while coasting

I have a 2004 wrx with all perrin parts you can buy, a stage three sti motor with forged internals managed by utec and a turbo xs tune. Mishimoto radiator with subaru coolant and silicone hoses, BC coilovers, Vf39 turbo, blitze nÜr exhaust, 800 cc injectors, crawford AOS, Turbo xs recirculating BOV and turbo xs intercooler and boost controller and several other mods. I just started having a problem where after driving ( especialy boosting hard while accelerating) that when I kick it out of gear to coast I go down to 10-15 lbs vacuum and my wide band read - - - lean off the chart. I have to tap the gas to get it to read normal and the slower I coast the more stoich I get. Also three times while driving on the highway Ill coast before getting to a toll or offramp and the gauges shut off, cel comes on and engine shuts off.. I am able to restart it by turning the key off and back on. If I stay in gear and let off the gas vacuum is normal and when I get out of gear it doesnt have this vacuum loss problem or fuel issue. it seams when I go from boost or low vacuum cruising to nut. that it has an issue. I have checked the fallowing: Intercooler and piping are sealed, BOV operates properly and opens and closes smoothly, MAF sensor is in perfect order, and vacuum lines are good and tight. Alarm is working properly ( aftermarket viper) Have not been able to data log due to a laptop fried a month ago. and the only codes I have gotten were missfire from the aftermarket injectors...Any help is appreciated....possible IAC valve????
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Last edited by Masterchief117; 07-14-2013 at 04:46 PM.
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Old 06-22-2013, 03:41 PM   #2
Phatron
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sounds like a leak between teh maf and turbo, that will cause lean all the time.

a boost leak will be lean under vaccum and rich in boost.
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Old 06-23-2013, 12:12 PM   #3
Masterchief117
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I will double check today. I have a perrin intake and didbt see anything before..but i do run 10.1 rich boosting and even idle it creaps up to 17 lean unless tap the gas...cruising it also now slowky goes from stoich to about 15.7 lean
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Old 06-23-2013, 12:34 PM   #4
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That is a boost leak. You have a leak after the turbo.

Lean in vaccum, rich under boost
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Old 06-23-2013, 01:05 PM   #5
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Its odd that it randomly started..so would it be pre turbo or post..i checked everything so i guess a ttip to turbo xs to have a pressure test done to the intercooler piping and all is required? Or is there an at home way...keep in mind my air compressor is at my brothers :-(
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Old 06-23-2013, 06:46 PM   #6
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its not odd that it randomly started...thats exactly how boost leaks are...all the sudden you pop a leak.

i said in my last post that the leak is AFTER the turbo.....

without an air compressor, you can spray brake cleaner while the car is idling and once you find the leak the car will stumble when it sucks in the cleaner. but that really doesnt work most of the time.
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Old 06-24-2013, 09:38 AM   #7
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Appreciate the input i have some starter spray. But as you said doubt it will work due to all the piping it would have to go through. Thank you, will post if i found the leak
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Old 06-27-2013, 04:16 PM   #8
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Originally Posted by Masterchief117 View Post
Appreciate the input i have some starter spray. But as you said doubt it will work due to all the piping it would have to go through. Thank you, will post if i found the leak
You'd be surprised at how quickly you find the leak with some starter spray. It gets ingested quickly and suddenly changes the way the engine runs.
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Old 07-14-2013, 03:29 PM   #9
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UPDATE: I found a major leak in my "S" pipe that goes from the intercooler through the pass side fender wall. The sheet metal had eaten through the gromet and into the pipe. HERES THE ISSUE! I welded the pipe tightly shut. I drove the car and didnt even make it out of my coldesack this time. Same symptoms only Im not loosing vacuum. The vacuum while coasting sits at 22 lbs, though like part of the origional problem, when I coast the faster I coast the leaner I run. If Im 40+ mph and coast out of gear Im lean off the chart and have to tap the gas to keep it withing range(bad batch of gas? I buy from shell or BP and havent ever had a problem thus far and while running lean I added Lucus octane booster to prevent detonation while running lean). Im still not hitting target boost, I should be hitting 19 at map 2 and IM getting15-16 lbs boost.The turbo is a vf 39 with 70k miles on it though. and when I am boosting I run rich too 10:1 !!! I took everything back off and re tested for another boost leak. NOTHING. All I could hear was the air going through the pipes. It was loudest by the intake/turbo outlet area but I didnt hear a hiss just air going through piping. what now????? Note: the gauge on the boost leak tester did slowly drop after air was removed. But its not escaping from the pipes anywhere. A little around where the tester was hooked to the intake but not sure if thats where all of it was going. The motor was leak down tested last summer (while motor was hot...subaru did it the first time COLD and said it had 30% on all cylinders.. they just wanted my $3k for a ring job..******** So i bought a snapon test gauge set and did it myself) and was about 10% on three cylinders and 13% on the 4th. It puffs a little smoke apon startup and when I first move the car in the driveway but only randomly and NOT often. I did have a decent amount of oil in my intake pipes and inter cooler, guess the crawford AOS isnt working too hot. Though as far as I know no smoke while driving unless I boost 21 lbs ( on map 1 ) and its a puff then as well. Motor has 50k and is tired but not dead. car idles fine and I replaced the IACV gasket and cleaned it last summer.

Last edited by Masterchief117; 07-14-2013 at 04:48 PM.
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Old 07-15-2013, 06:43 AM   #10
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Bad coilpack cause this? A friend had a bad one caused the a/f issues..or a nad 02 sensor? I dont have.codes for it because they were.deleted, but could that be bad?

Last edited by Masterchief117; 07-15-2013 at 07:14 AM.
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Old 07-19-2013, 10:32 PM   #11
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Quote:
Originally Posted by Phatron View Post
its not odd that it randomly started...thats exactly how boost leaks are...all the sudden you pop a leak.

i said in my last post that the leak is AFTER the turbo.....

without an air compressor, you can spray brake cleaner while the car is idling and once you find the leak the car will stumble when it sucks in the cleaner. but that really doesnt work most of the time.
Take a propane camping cylinder and hook up a hose... Run it around the engine bay. This works all the time.
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Old 07-19-2013, 10:32 PM   #12
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Quote:
Originally Posted by Masterchief117 View Post
Bad coilpack cause this? A friend had a bad one caused the a/f issues..or a nad 02 sensor? I dont have.codes for it because they were.deleted, but could that be bad?
What's the voltage on the live data?
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Old 08-20-2013, 10:07 PM   #13
Masterchief117
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I know this is an old topic, and I meant to get back on and let anyone know who this may help in the future what I found. I had a coil pack going bad and the bank one 02 sensor was trashed. all codes for 02 sensors had been deleted in tuning at turbo xs and as it turned out, i replaced the number 3 coil pack and front 02 sensor..a few drive cycles later all my problems were solved. cats be about $400 in parts at subaru but I got it all done. Thank you very much to everyone for their input throughout this process!!
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Old 08-21-2013, 03:41 AM   #14
Phatron
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how is deleting the cel's for the sensor that controls the fueling for the car the answer to anything? I don't get it
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Old 08-21-2013, 03:44 AM   #15
Phatron
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Quote:
Originally Posted by Antiharper View Post
Take a propane camping cylinder and hook up a hose... Run it around the engine bay. This works all the time.
and no...spraying brake cleaner or any other chemical into the engine bay doesn't work "all the time". if you think all leaks present themselves at vacuum at idle....you are sorely mistaken.

take a rubber hose with a hole in it and pull vacuum on it, then put 30psi through it and see how the hole reacts
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