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Thread: Replace MAP sensor vacum line

  1. #1

    Default Replace MAP sensor vacum line

    Hi everyone.
    Is it possible to replace the vacuum line to the MAP sensor without removing the intake? The line from the intake is dry rotted and collapses. Itís probably the original line. Itís a 1990 Colony Park that is all stock.

  2. #2
    2 decades of DDing Box Panthers, now in a Whale VicCrownVic's Avatar
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    I don't remember if that one goes all the way under the intake. If it does, there's not much chance of replacing it with out at least lifting the upper intake. May not have to disconnect everything, just lift enough to get under the upper intake, but then you run the risk of breaking the brittle plastic (1/8"?) vac lines.
    Vic

    ~ 1998 Mercury Grand Marquis LS - new DD
    ~ 1991 Mercury Grand Marquis LS "The Scab" - plenty of rot, summer DD
    ~ 1997 GMC Yukon - wannabe winter DD - returning sometime in the 2020s, I finally have an engine
    ~ 1991 Mercury Grand Marquis GS "The Ice Car" - Rotting Retired Winter DD
    ~ 1989 Mercury Grand Marquis GS - Rotting Retired DD
    Gone but not forgotten:
    ~ 1988 Country Squire ~ 1987 Ford Crown Vic

  3. #3

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    Thank you VCV. Iím looking into using medical clamps, the old roach clip kind and a mirror to see what Iím doing coming in from the firewall side. The clamps I have are too large and need to get a medium size. I just now thought about using a flexible tool grabber cable that may work to get it off.

  4. #4

    Default

    If the MAP sensor line is cracked, there are likely other cracked lines.
    In fact, the MAP sensor line might be fine and the lines from the same vacuum tee might be leaking enough to skew the vacuum reading.

    Since so many of the vacuum lines are under the intake, and hard to see (but easy to disturb); and since the upper intake usually comes off pretty easily (especially if you're just moving it slightly to get the vacuum lines, and not removing it from the car, so you can leave the throttle body stuff in place); why not replace all the vacuum lines and then not have to worry about it for another decade or more?

    I bet the time and cost of the work won't be a whole lot more than you were planning on already, and it's much, much easier to use your hands and eyes without mirrors and medical clamps.

  5. #5
    2 decades of DDing Box Panthers, now in a Whale VicCrownVic's Avatar
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    Also, if I'm not mistaken, the vac line at the intake connects to a much larger barb than at the MAP. If you got a line to fit the MAP it will be way too small for the intake end.
    Vic

    ~ 1998 Mercury Grand Marquis LS - new DD
    ~ 1991 Mercury Grand Marquis LS "The Scab" - plenty of rot, summer DD
    ~ 1997 GMC Yukon - wannabe winter DD - returning sometime in the 2020s, I finally have an engine
    ~ 1991 Mercury Grand Marquis GS "The Ice Car" - Rotting Retired Winter DD
    ~ 1989 Mercury Grand Marquis GS - Rotting Retired DD
    Gone but not forgotten:
    ~ 1988 Country Squire ~ 1987 Ford Crown Vic

  6. #6

    Default

    It's been a little while but I think the vacuum tree under the intake has a small line for the MAP, a larger line to the splitter on the firewall (which feeds cruise, HVAC, etc) and a line or two to the evap and egr?
    Again, once they start cracking and coming apart I figure I'm going to end up doing them all eventually, I'd rather do it once and be done.

  7. #7

    Default

    Thanks again VCV and BGW.
    So far the plastic hoses look ok.
    The line coming from the intake is rubber and connects into an adapter fitting that adapts to a smaller hose to the MAP sensor. THANKS AGAIN and I will update.

  8. #8
    2 decades of DDing Box Panthers, now in a Whale VicCrownVic's Avatar
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    They may look ok, and functionally be fine, but one wrong move and they snap easy (which may be part of your concern of not wanting to remove the upper intake). Don't even sneeze on those tiny plastic lines, LOL.

    My fix in that case is to insert both ends of broken plastic line into a piece of vac hose with 1/8" ID. If it doesn't break into a million pieces or too close to the end.
    Last edited by VicCrownVic; 03-19-2021 at 12:55 PM.
    Vic

    ~ 1998 Mercury Grand Marquis LS - new DD
    ~ 1991 Mercury Grand Marquis LS "The Scab" - plenty of rot, summer DD
    ~ 1997 GMC Yukon - wannabe winter DD - returning sometime in the 2020s, I finally have an engine
    ~ 1991 Mercury Grand Marquis GS "The Ice Car" - Rotting Retired Winter DD
    ~ 1989 Mercury Grand Marquis GS - Rotting Retired DD
    Gone but not forgotten:
    ~ 1988 Country Squire ~ 1987 Ford Crown Vic

  9. #9
    GMN Regular DerekTheGreat's Avatar
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    You will never get the old hoses off unless you remove the upper. I had one upper off and it was still a pain in the ass to get the hoses off, ended up cutting them with a razor blade. Your back will thank you. Like others said, it'll give you a chance to replace all the other lines which need to be replaced.
    1985 LTD Crown Victoria - SOLD
    1988 Town Car Signature - Current Party Barge

  10. #10
    I'm an air-conditioned gypsy gadget73's Avatar
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    for the effort involved in trying to not remove 6 bolts, I would say its not worth it. You can get the upper intake off these cars in like 10 minutes.

    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

  11. #11

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    Guess I'll replace the fuel injectors then.
    I didn't want to deal with an intake gasket.

  12. #12
    2 decades of DDing Box Panthers, now in a Whale VicCrownVic's Avatar
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    I've reused the upper to lower intake gasket, you'll be fine there.
    Vic

    ~ 1998 Mercury Grand Marquis LS - new DD
    ~ 1991 Mercury Grand Marquis LS "The Scab" - plenty of rot, summer DD
    ~ 1997 GMC Yukon - wannabe winter DD - returning sometime in the 2020s, I finally have an engine
    ~ 1991 Mercury Grand Marquis GS "The Ice Car" - Rotting Retired Winter DD
    ~ 1989 Mercury Grand Marquis GS - Rotting Retired DD
    Gone but not forgotten:
    ~ 1988 Country Squire ~ 1987 Ford Crown Vic

  13. #13
    I'm an air-conditioned gypsy gadget73's Avatar
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    no need to replace the injectors.

    and +1 on recycling the gasket. I've re-used them several times. Just be careful and try to not damage it. If it does rip its not very expensive.

    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

  14. #14

    Default

    I have a set of new rebuilt injectors on the shelf.
    The car has at least 82,000 miles and thought I might as well do it at the same time.

  15. #15
    I'm an air-conditioned gypsy gadget73's Avatar
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    well in that case, may as well. No better time to do valve cover gaskets either if they have any leaks
    before long we'll have you replacing the engine because its only a little bit more work

    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

  16. #16

    Default

    Good point Gadget.
    I hope not. This one is very original from Arizona with low miles. It still has desert dust on it.

    The other 90 wagon is doing well, always starting. Very smooth idle and driving. Replacing the ECT did it.
    I saw that Bernie has placed the ACT at the back of the upper intake.
    My mpg did go up 2 mpg.
    Maybe more when I fill up again.
    The shifting is very subtle at low throttle but it noticeable at full throttle.
    When I have the transmission fluid changed I will look into the governor.
    I THANK YOU always for all of your help.
    Mike

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