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Thread: PCV System

  1. #1
    Member BigT's Avatar
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    Question PCV System

    Itís been about 2 years now, but I got the old girl running great again!

    I had to change out the fuel pump and in-tank rubber hose attached to the fuel pump. I got most of the dash back together, at least enough so I can drive it. I found where my massive vacuum leaks came from and fixed it. The Dorman rubber caps I put on to cap off the large vacuum ports under the top intake cracked. One cracked so bad it was almost in half! I replaced the ignition switch. And I replaced the Mega Squirt computer with a Speed Density Mustang computer.

    It was running so good, I had my wife follow me around town. She said the car smelled like it had Ďalotí of exhaust. Not rich, like too much gas, but a really strong exhaust smell. I pulled away from her at one point, but she said she could tell where I was by following the exhaust smell. She also said if I wanted to do myself in, just start that car in a closed garage and youíll be gone in a minute!

    I looked the PCV system I had set up and realized I didnít have any fresh air going into the system. I put on a breather filler cap and routed the PCV valve to a catch can and then to back to the intake vacuum. No more smell.

    But I got to thinking about the PCV system. This setup is working for me now as Iím running Speed Density, but what happen if I convert to Mass Air Flow? Would it be an unmetered air source? Or is the amount of air so small the MAF computer will adjust for it? If not, what is the proper setup for a MAF PCV system?

    I still have many items to fix on the car, but its great having her on the road again!




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  2. #2
    GMN Regular DerekTheGreat's Avatar
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    Hey yeah, glad to see you're back T. I think I remember when you were in the process of the HO swap. Nice to know you've still got the car.
    1985 LTD Crown Victoria - SOLD
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  3. #3
    Member BigT's Avatar
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    Yes, I was doing a HO swap that went horribly badÖwellÖI thought it went bad. It was really all these other things that were causing me problems.

    The backfiring was caused by a cracked rubber hose connected to the fuel pump inside the tank. That was my fault. In anticipating the HO upgrade a few years earlier, I upgraded to a Mustang fuel pump. I didnít read the instruction to use a fuel injection hose instead of a regular fuel hose. After a few years the hose swelled and cracked open losing fuel pressure to feed the injectors. Plus, the huge vacuum leaks contributed to the lean backfiring.

    The next issue was the car dying. It would start, then immediately die. I found the cause by accident. As I slowly turn the ignition key back and forth, I could hear all the clicks of the starting and stopping process. I notice that if the key went back just a little, it would cut off the engine. So, if I started the car and NOT let it go back to ĎRUNí by the force of the spring, the car would stay running. But if you bump the key, it would shut off the car.

    Now on to the Mega Squirt computer. Because of the low fuel pressure and too much vacuum leak, I canít blame it for not running right. I can blame it for cutting off my A/C because of a WOT signal. No A/C in Alabama is a killer! The companyís fixÖcut the signal wire to the relay preventing it from cutting off the A/C. Seems to me there could be a software check box that could do that, but no you need to cut the wire. Maybe because this is a Grand Marquis and not a Mustang. BTW, no A/C was one of the reasons I had the dash torn apart. The other reason was the to repair the blend door. Which works great now! A/C is nice a cold. I would like to give the Mega Squirt another try, but itís such a pain in the butt to change out. I wish it was in a location and easy as the Mustangs.

    I found the vacuum leaks just a few days ago. I could not believe my eyes how badly cracked and open those vacuum caps were!

    Due to health issues with me and a couple of family members, I was only able to tinker with the car now and then. The car sat for so long, squirrels made it a home. They chewed off my windshield wash spritzer wiring and a few other places.

    For the PCV, Iím thinking of keeping everything the same, but having the fresh air come in from the throttle body hose to the oil filler neck. That should keep it from introducing none metered air into the system. What do you think?




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  4. #4
    GMN Regular DerekTheGreat's Avatar
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    Wow, quite the stories. Lots of headaches I doubt I'd be able to find so good on ya for that. I'll definitely keep those things in mind when tinkering. Sucks about the A/C & Megasquirt. So MS always "sees" a WOT signal thus cutting off the A/C? Also sucks about the squirrels. I hate those fuckin' things. Was digging old nest material from my truck's passenger side fender this weekend, no wonder the fender is rotten...

    Err I thought PCV fresh air does come from the TB? I was just under the hood of my TC yesterday and it's got a black tube going from the TB to the filler neck just as you describe.
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  5. #5
    The Brown Blob 87gtVIC's Avatar
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    In stock form it does for both maf and mafless equipped vehicles of that era. The fresh air is metered though because it comes in after the maf.
    ~David~

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    Quote Originally Posted by DerekTheGreat View Post
    But, that's just coming from me, this site's biggest pessimist. Best of luck

  6. #6
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    Just a side note, I had the exact same experience with the black rubber Dorman vacuum caps. I believe they're intended only for temporary diagnosis work, not permanent installation, or at least they should be, because they do not last long at all.

    The multi-coloured Dorman vacuum caps, on the other hand, are fine for long term use.

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  7. #7
    I'm an air-conditioned gypsy gadget73's Avatar
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    Stock PCV system does pull fresh air off the elbow on the throttle body. As long as that is the only place air is going to the crankcase, you won't have an unmetered air source. If its pulling straight from atmosphere, its a vac leak as far as a MAF setup is concerned.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

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    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  8. #8
    Member BigT's Avatar
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    Quote Originally Posted by DerekTheGreat View Post
    ÖSucks about the A/C & Megasquirt. So MS always "sees" a WOT signal thus cutting off the A/C?
    Yes, either it sees it or sends it to the A/C cut-off relay. The tech I was talking to could only offer me the wire snipping solution.

    Quote Originally Posted by DerekTheGreat View Post
    Also sucks about the squirrels. I hate those fuckin' things. Was digging old nest material from my truck's passenger side fender this weekend, no wonder the fender is rotten...
    I lost the low beams a couple days ago. Not sure what they did, the high beams worked fine. Today I got a new relay and redid all the low wiring. Now I have headlights again!

    Quote Originally Posted by DerekTheGreat View Post
    Err I thought PCV fresh air does come from the TB? I was just under the hood of my TC yesterday and it's got a black tube going from the TB to the filler neck just as you describe.
    Quote Originally Posted by 87gtVIC View Post
    In stock form it does for both maf and mafless equipped vehicles of that era. The fresh air is metered though because it comes in after the maf.
    Quote Originally Posted by gadget73 View Post
    Stock PCV system does pull fresh air off the elbow on the throttle body. As long as that is the only place air is going to the crankcase, you won't have an unmetered air source. If its pulling straight from atmosphere, its a vac leak as far as a MAF setup is concerned.
    Yep, after stepping back and relooking at the setup, thatís the best way to go. During my past tinkering, I just didnít put it back right. I can see how it will be metered now.

    Quote Originally Posted by kishy View Post
    Just a side note, I had the exact same experience with the black rubber Dorman vacuum caps. I believe they're intended only for temporary diagnosis work, not permanent installation, or at least they should be, because they do not last long at all.

    The multi-coloured Dorman vacuum caps, on the other hand, are fine for long term use.
    Thanks, using them now!




    I'd rather be a failure at something I love than a success at something I hate.
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  9. #9
    I'm an air-conditioned gypsy gadget73's Avatar
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    Does the MS drive the relay in the opposite manner as the stock stuff? The stock ECM powers the relay to disengage the AC. If the MS arrangement drops power to the relay, then the fix is simply moving the wire in the AC relay socket from the NC connections to the NO connections.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  10. #10
    Member BigT's Avatar
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    Quote Originally Posted by gadget73 View Post
    Does the MS drive the relay in the opposite manner as the stock stuff? The stock ECM powers the relay to disengage the AC. If the MS arrangement drops power to the relay, then the fix is simply moving the wire in the AC relay socket from the NC connections to the NO connections.
    MS tells the A/C relay the throttle is wide open, all the time. I'm not sure if it is sending power to the relay, or cutting power to the relay to cause the problem. I do know that if I go with the MS, I will have to cut the wire talking to the A/C relay in order to have A/C. Which will cause the A/C to continue to run even when I do go WOT. With MS I cannot have it both ways.

    From my e-mail/forum (MSPNP=Mega Squirt Plug-N-Play):
    --------------------------------------------------------------------------------------------------------------
    Correct, the MSPNP does not have a WOT cutoff function normally.
    Thanks,

    Matt Cramer
    DIYAutoTune.com support


    On 8/2/2016 6:39 AM, Tom wrote:
    Matt,

    Thank you for answering my e-mail and post. I'm wondering if snipping that wire will it make the WOT relay stop functioning? Meaning after I snip this wire, when I floor it, the A/C clutch will not disengaged and keep running?

    Tom

    http://www.msextra.com/forums/viewto...=grand+marquis
    --------------------------------------------------------------------------------------------------------------

    This seems like a short coming of MS. Since the current SD HO Mustang ECM I'm using gives me both, I would think MS could too. And from my MAF research, I did NOT see folks with A/C problems after their conversion. So it makes me lean towards selling the MS and going with MAF.




    I'd rather be a failure at something I love than a success at something I hate.
    George Burns

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