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Thread: 1987 Town Car running rich? High IDLE. Poor MPG

  1. #1

    Default 1987 Town Car running rich? High IDLE. Poor MPG

    1987 Town Car. Stock Drivetrain with Dual Exhaust no Cats. Recent Spark plugs, wires and cap, no rotor. Averaging 15mpg. I know this car will average 18 or more like it used to when it was like new. I suspect the elimination of the catalytic converters with my new dual exhaust is the reason that it is running rich. What can I do about this? Idling high, cruise control is out as well.

  2. #2
    I post a lot...
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    Sounds more like a vacuum leak.

    85 4 door 351 CV - 160KMs stock and with issues... 4BBL swap and other goodies in the spring...next spring

    06 Mazda 3 hatch 2.3L 5AT (current daily)

  3. #3
    Proud Owner Of A 1987 Mercury Grand Marquis! miamibob's Avatar
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    Why do all that and no rotor? You were in there to do the cap! Could be vac or also check TPS, IAC and O2 sensors.

  4. #4
    fuck no, not today, thank you kindly 1990LTD's Avatar
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    Unless your rotor looked perfect you should always replace it when you do the cap etc. 5 bucks at the most.


    Converters on these cars have SFA to do with how much gas she burns, the o2 sensor is up in the exhaust manifold so it gets a signal pre-converter anyway in stock form. I got a bump in gas mileage when I went from a stock single exhaust to 2.25 dual pipes and no converters. A drop makes no sense, so a vacuum leak would be my first guess.


    do you know how to check for leaks?



    When you got rid of the converters, what was done to the air pump plumbing that used to run down to the cats?
    Last edited by 1990LTD; 09-24-2011 at 02:23 PM.
    - 1990 Ford LTD Crown Victoria P72 - the street boat - 5.0 liter EFI - Ported HO intake/TB, 90 TC shroud/overflow, Aero airbox/zip tube, Cobra camshaft, 19lb injectors, dual exhaust w/ Magnaflows, Cat/Smog & AC delete, 3G alternator, MOOG chassis parts & KYB cop shocks, 215/70r/15s on 95-97 Merc rims - Summer toy/work in progress.

    - 2007 Ford Escape XLT - soccer mom mobile - 3.0 Duratec - Daily Driver/Beater/Hauler of parts and contraband

  5. #5
    I post a lot...
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    I'm interested too.
    Since doing my HO swap; my first gas tank was 10mpg, my second gas tank was 12.5mpg.

    My major commute with the old lopo used to be 20miles to school and back, and 20mpg was common. 18mpg wintertime. 24mpg best tank ever.
    I now commute 5 miles to work, 5miles back. So I realize that shorter trips could be a part of it; and having fun with the new engine that first tank could have been part of the 10mpg. I also don't know if a just-rebuilt engine needs to break in a little; if internal frictions are high.
    But this had better not be a longterm average.

    So I'm interested in some of these responses also.
    Could an exhaust leak, such that the O2 sensor sees less exhaust, cause rich-running issues?
    Granted I have no idea if I'm running lean, rich, or just right-- worth finding a friend with a tailpipe sniffer?

    And I wouldn't mind a description of how to test for vacuum leaks. I presume the same smoke test I've used for emissions system leaks, would do the same job; and watch for a flow rate? flow rate = leak, no flow=contained? If there is flow, look for smoke somewhere?
    Last edited by BerniniCaCO3; 09-24-2011 at 02:57 PM.

  6. #6
    Abolish the act of 1871 Lincolnmania's Avatar
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    replace all the dead vacuum lines, you will have to pull the upper intake to get at a few.......little trick i use is to blow smoke into one of the vacuum lines and look for smoke to escape.

    i see no mention of changing the pcv valve screen and grommet the screen gets clogged and the grommet turns to rock.......the pcv hose also turns to rock

    1986 lincoln towncar signature series. 5.0 HO with thumper performance ported e7 heads, 1.7 roller rockers, warm air intake, 65mm throttle body, 1/2" intake spacer, ported intakes, 3.73 rear with trac lock, 98-02 front brake conversion, 92-97 rear disc conversion, 1" rear swaybar, 1 3/16" front swaybar, 16" wheels and tires, loud ass stereo system, badass cb, best time to date 15.94 at 87 mph. lots of mods in the works 221.8 rwhp 278 rwt
    2006 Lincoln Town Car Signature. Stock for now
    1991 lincoln mark VII bill blass (Buy me!)
    1982 efm and 1986 alaska stokers keeping me warm

  7. #7
    Fastest Box In South Jersey 86VickyLX's Avatar
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    I second the PCV filter. Unless you like changing gaskets frequently...
    "Vicky" 1986 Ford LTD Crown Victoria LX ..................................."Blue" 1992 Mercury Grand Marquis LS

    Vicky
    Too much stuff to list in my signature...
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  8. #8
    I'm an air-conditioned gypsy gadget73's Avatar
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    high idle + poor economy almost always means vacuum problems. Yank the intake, change the hoses, and replace the PCV junk while you're in there. If the valve covers leak, change those too.

    86 Lincoln Town Car (Galactica).
    Drivetrain: 5.0 HO, Explorer cam, FMS 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley, SuperCoupe stall converter

    Suspension: Bridgestone Protenza G019 225/60/16 on LSC turbines, 1 3/16" wagon front bar, 1" PI rear bar, cargo coils, KYB GR-2 front shocks, F150 rear air shocks, big front brakes, ES poly front suspension bushings, 00 CVPI steering box, ES poly body mounts, rear disc brakes

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks.

  9. #9

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    Allright guys. I just replaced the Rotor yesterday too. I will begin the rest of the project by next weekend. Hunting down any vacuum leak.

  10. #10

    Default

    Allright guys. I just swapped a newer coil from a Foxbody 5.0 and replaced the Rotor yesterday too. I will begin hunting down the vacuum leak next. The car seems to be sucking down a quart of oil per week too.

  11. #11
    Abolish the act of 1871 Lincolnmania's Avatar
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    valve cover gaskets and lower intake gasket for sure.....make sure to use felpro permadry gaskets

    1986 lincoln towncar signature series. 5.0 HO with thumper performance ported e7 heads, 1.7 roller rockers, warm air intake, 65mm throttle body, 1/2" intake spacer, ported intakes, 3.73 rear with trac lock, 98-02 front brake conversion, 92-97 rear disc conversion, 1" rear swaybar, 1 3/16" front swaybar, 16" wheels and tires, loud ass stereo system, badass cb, best time to date 15.94 at 87 mph. lots of mods in the works 221.8 rwhp 278 rwt
    2006 Lincoln Town Car Signature. Stock for now
    1991 lincoln mark VII bill blass (Buy me!)
    1982 efm and 1986 alaska stokers keeping me warm

  12. #12
    I'm an air-conditioned gypsy gadget73's Avatar
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    yup, they're spendy but they last. The cork ones do not. 40 bucks for the valve cover gaskets but you'll never have to touch it again.

    86 Lincoln Town Car (Galactica).
    Drivetrain: 5.0 HO, Explorer cam, FMS 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley, SuperCoupe stall converter

    Suspension: Bridgestone Protenza G019 225/60/16 on LSC turbines, 1 3/16" wagon front bar, 1" PI rear bar, cargo coils, KYB GR-2 front shocks, F150 rear air shocks, big front brakes, ES poly front suspension bushings, 00 CVPI steering box, ES poly body mounts, rear disc brakes

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks.

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