Boost control solenoid test
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This is a discussion on Boost control solenoid test within the Tutorials & DIY forums, part of the Tech & Modifying & General Repairs category; Having boost issues in an 02 Wagon, manual trans, no aftermarket parts, no tune, 200K miles. it's was running half ...

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    Boost control solenoid test

    Having boost issues in an 02 Wagon, manual trans, no aftermarket parts, no tune, 200K miles. it's was running half pressure. I put a new restrictor pill on because the line was cracked and the new pill made it have bad fluctuation. Then it started running half again after 2 days. I hooked the BCS directly up to 12V and I can hear it working however, I dont know if that means it's a good part. Any thoughts?

    Called 2 different shops here in Dallas. One said it was the Wastegate actuator, and the other (cobb tuning) said "no that's not it, you probably have a vacuum leak somewhere."

    Im am getting a divorce so money is super tight right now. I can't afford to buy parts that aren't the issue, sooo..... Help me please.

    Side note: my bugeye has most of the typical issues that I've seen on these cars. Clock is broken, boost issues, oil leak near turbo, stock radio CD issue, etc...
    Last edited by Doris; 05-01-2016 at 10:41 AM. Reason: Clarity

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            MainFrame's Avatar
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    Vacuum leak is probably the most likely problem.. I would check over everything closely to look for any worn out hoses, anything that doesn't look right really, clean the grounds, clean the MAF (probably clean the throttle body too). Then I would make a boost leak tester, plug it into the inlet, cap off all the vacuum lines, air it up to about 15psi and see if it holds. If you hear air hissing anywhere find it and fix the leak. After that reset the ECU and go for a drive.. just a normal drive, don't beat on it or anything. Once you've driven it 30-50 miles check it out and see if the issue is fixed.


    You can also put the car into test mode by plugging the green connectors together under the dash and see if it cycles the BCS.. supposedly you should be able to hear it clicking on and off, although I've never been able to diagnose a BCS that way. It's pretty uncommon for them to fail, and there are a lot more likely reasons why you could have low boost.

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    Thank you. I'm under the hood right now cleaning. I'll search high and low. This is an annoying problem.

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    Update: I cleaned the MAF. In the process I found 2 vacuum leaks, caused 2 more, fixed them all. But I broke the purge valve and the blue T that's right next to it. A lot of stuff is very brittle. For the time being I've deleted it. I fixed it with some epoxy but it has to cure over night. The purge solenoid is still under vacuum and still plugged in. Now I'm back to the bad boost fluctuation. Overboosting the dropping and instantly building back up. Im have no idea what's happening.
    Also there's a short hose on the drivers side beside the washer fluid reservoir, crankcase breather maybe? I dunno. But it was connected to nothing. No idea how long it was like that but judging by the way it was sitting it had been a long time.

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            MainFrame's Avatar
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    Quote Originally Posted by Doris View Post
    Also there's a short hose on the drivers side beside the washer fluid reservoir, crankcase breather maybe? I dunno. But it was connected to nothing. No idea how long it was like that but judging by the way it was sitting it had been a long time.

    It was connected to nothing on either end? Over on that side you should have hoses from the manifold connected to the brake booster, fuel pressure regulator, bypass valve, and boost gauge if you have one.


    You can't verify that all the leaks are fixed without doing a boost leak test first.. if you air it up and it holds pressure then you're good, if you just fix what you can see you have no idea if it's actually fixed or not. And if it's over boosting and oscillating that badly you're doing permanent damage to the engine by driving it.

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    There are most likely still leaks. And I'm keeping my foot out of it till I get this figured out. The hose I'm taking about is right behind the rear spark plug. If you remove the washer fluid jug its right there. The bottom was connected nothing.
    Last edited by Doris; 05-02-2016 at 09:43 AM. Reason: Typo

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            MainFrame's Avatar
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    Quote Originally Posted by Doris View Post
    The bottom was connected nothing.

    And the top was connected to.... ?

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    Bottom of the hose is the valve cover vent. The top of that hose feeds back into the intake manifold under the intake runners just to the driver side of the throttle body

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            MainFrame's Avatar
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    Ahh.. then that's just the vent for the driver's side head.

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    Quote Originally Posted by MainFrame View Post
    Ahh.. then that's just the vent for the driver's side head.
    The max mpa I get is .11 or 16psi and it drops to .05 mpa. Back and forth. Looks like a metronome

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