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    #1

    bad iac valve?

    I've read about folks getting a bad TPS but don't recall if I ever saw IACs mentioned. The one I got from RockAuto wouldn't let my car idle right..kept surging and stalling.

    I had been mucking with vacuum lines and removing unnecessary ones so I originally thought I had a vacuum leak but eventually (after also trying another TPS, also new).

    I tried unplugging the valve - did nothing, disconnecting the valve shot the engine speed through the roof (no idea what it revved up to, didn't stop to check before I turned it off as quickly as possible). It would also make a sucking sound for over a second after I turned the car off, no CEL though. Disconnect battery, install old IAC, wait, reconnect battery, car runs
    "fine", same as it did before I put the new one on. It's not perfect, hence buying the new valve.

    I emailed RockAuto about it. It wasn't really expensive and they've replaced stuff for me in the past so I don't expect this to be a big hassle. I'd be happy with credit towards a Motorcraft unit.


    ever get a bad one right out of the box? have any other brand new parts be junk?
    Last edited by 1990LTD; 10-13-2010, 02:20 AM.
    sigpic


    - 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

    - 2007 Ford Escape XLT - soccer mom lifted station wagon - 3.0 Duratec, auto, rear converter delete w/ Magnaflow dual exhaust

    - 2008 Mercury Grand Marquis Ultimate Edition - Daily driver - 4.6 2 valve Mod motor, 4R75E, 2.73s. Bone stock
    Tags: None
    #2
    Yes, have gotten a bad IAC out of the box. So have several others. Have had better luck with junkyard IAC's than new ones.
    Originally posted by gadget73
    There is nothing more permanent than a temporary fix.
    91 Mercury CP, Lopo 302, AOD, 3.08LSD. 3g upgrade, Moog wagon coils up front, cc819s in the back. KYB GR-2 police shocks. Energy suspension control arm bushings. Smog deleted.
    93 F-150 XLT, 302, ZF 5-spd from 1-ton, 4wd.
    Daily--07 Civic Coupe. Bone stock with 25k miles
    Wife--14 Subaru Outback. 6-speed.
    95 Subaru Legacy Wagon--red--STOLEN 1/6/13

    Comment

      #3
      I think a good IAC is supposed the stall the motor when you unplug it...
      Pete ::::>>> resident LED addict and CFI defector LED bulb replacements
      'LTD HPP' 85 Vic (my rusty baby) '06 Honda Reflex 250cc 'Baileys' 91 Vic (faded cream puff) ClifFord 'ODB' 88 P72 (SOLD) '77 LTDII (RIP)
      sigpic
      85HPP's most noteworthy mods: CFI to SEFI conversion w/HO upperstuff headers & flowmasters P71 airbox Towncar seats LED dash light-show center console w/5 gauge package LED 3rd brake light 3G alternator mini starter washer/coolant bottle upgrade Towncar power trunk pull underhood fuse/relay box 16" HPP wheels - police swaybars w/poly rubbers - budget Alpine driven 10 speaker stereo

      Comment

        #4
        MrMarquis had a bad brand new IAC on his car. It gave codes for idle too high and idle too low at the same time during a self test. That sounds like it ought to be impossible, but thats what it did. It just wouldn't idle quite right either. Stuck a used Motorcraft part on, the codes cleared, and the idle was normal again. I think thats gonna have to be one of those parts thats Motorcraft or nothin.
        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 grandpa spec white and cranberry

        1984 Lincoln Continental TurboDiesel - rolls coal

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

        Comment

          #5
          Originally posted by 85crownHPP View Post
          I think a good IAC is supposed the stall the motor when you unplug it...

          yeah, absolutely no change when I unplugged it
          sigpic


          - 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

          - 2007 Ford Escape XLT - soccer mom lifted station wagon - 3.0 Duratec, auto, rear converter delete w/ Magnaflow dual exhaust

          - 2008 Mercury Grand Marquis Ultimate Edition - Daily driver - 4.6 2 valve Mod motor, 4R75E, 2.73s. Bone stock

          Comment

            #6
            yeah thats most likely fried, or someone has jacked around the throttle stop screw so the idle is way above what the ecm can control.
            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 grandpa spec white and cranberry

            1984 Lincoln Continental TurboDiesel - rolls coal

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

            Comment

              #7
              rockauto think it's because it's not the right one for my car (federal vs California emissions)..I bought the federal version because it's not a California car. The only visible difference in the valves in their catalog is the angle of the plug..one is at a right angle and the other straight out...but the valve I have looks the same as the valve I bought. whatever, I've saved enough money through them to write this one off as a learning experience (BUY OEM)
              sigpic


              - 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

              - 2007 Ford Escape XLT - soccer mom lifted station wagon - 3.0 Duratec, auto, rear converter delete w/ Magnaflow dual exhaust

              - 2008 Mercury Grand Marquis Ultimate Edition - Daily driver - 4.6 2 valve Mod motor, 4R75E, 2.73s. Bone stock

              Comment

                #8
                california



                federal

                sigpic


                - 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

                - 2007 Ford Escape XLT - soccer mom lifted station wagon - 3.0 Duratec, auto, rear converter delete w/ Magnaflow dual exhaust

                - 2008 Mercury Grand Marquis Ultimate Edition - Daily driver - 4.6 2 valve Mod motor, 4R75E, 2.73s. Bone stock

                Comment

                  #9
                  its the same part, just one has a 90. The 90 is actually normally found on Fox cars with the intake facing the other way since you cant plug it in on a Panther once its bolted up. You can use one, just plug in the connector before bolting it to the engine.
                  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 grandpa spec white and cranberry

                  1984 Lincoln Continental TurboDiesel - rolls coal

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

                  Comment

                    #10
                    ^Or you can unscrew the motor from the pintel part and rotate it 90 degrees.^


                    My idle screw if I pull it out anymore it doesn't contact the throttle bracket. A lot good that does. My car will idle with the iac unplugged. It won't high idle of course.

                    Comment

                      #11
                      the ones that idle high with the screw backed out all the way and an HO or Explorer throttle body can be fixed with a pop rivet in the small hole through the throttle blade. I suppose soldering the hole shut and re-drilling the solder blob with a smaller drill also works but the pop rivet gets the job done.
                      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 grandpa spec white and cranberry

                      1984 Lincoln Continental TurboDiesel - rolls coal

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

                      Comment

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