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    #1

    Throttle Position Sensor gives high voltage readings...

    I own a 1983 Grand Marquis, and it hesitates when I try to accelerate from a stopped position. I have changed the spark plugs, spark plug wires, and fuel filter. I then checked the voltage readings from the throttle position sensor (TPS), and it was giving high voltage readings (from 2 v at no throttle, to 8 v at full throttle). I replaced this TPS with a new one, and got the SAME readings. So I'm assuming I found the problem, but I'm not sure what this means.

    I can't find any definitive answers online anywhere. What do these high readings mean? Is the ECM shot and in need of replacing? Thanks for the help!!
    Tags: acceleration problem, engine pause, slow acceleration
    #2
    Reference voltage to a TPS should be at or near 5v. Full throttle reading should be really close.
    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

      #3
      is it throttle body injection (CFI) or a 351 and have a carburetor? I don't think it'll actually make a difference in the diagnosis, but the older car gurus around here might need that info. I'm also pretty sure that 1990LTD is right about the voltage shouldn't be higher than 5V. If that is the case, then you probably need an ECM or a voltage regulator for the alternator (or both).

      Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
      rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

      Originally posted by gadget73
      ... and it should all work like magic and unicorns and stuff.

      Originally posted by dmccaig
      Overhead, some poor bastards are flying in airplanes.

      Comment

        #4
        The 5v reference is pretty common today but I don't know about a car that old.
        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

          #5
          yeah... that's why I'm wanting gadget or someone that knows those older systems to comment.

          Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
          rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

          Originally posted by gadget73
          ... and it should all work like magic and unicorns and stuff.

          Originally posted by dmccaig
          Overhead, some poor bastards are flying in airplanes.

          Comment

            #6
            Sorry for not including this in the original post... it's a CFI 5.0 engine. And EVERYTHING I've found online says the same thing 1990LTD is saying: that the TPS receives a base 5 volts, and it shouldn't have a reading above that. But I just can't find any info on what that means if the reading is too high. Since I the old TPS and the new TPS give the same readings, I'm assuming it's some other component, I'm just not sure which one to target going forward.

            Comment

              #7
              definite test... disconnect the TPS, turn the car on, but do not start the engine. read the voltages in the wires and see if there's a good 5 volts coming from that reference pin. If it's higher, it's the ECM. If it's 5V... the problem may be in the charge circuit from the alternator (may need a new regulator).

              Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
              rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

              Originally posted by gadget73
              ... and it should all work like magic and unicorns and stuff.

              Originally posted by dmccaig
              Overhead, some poor bastards are flying in airplanes.

              Comment

                #8
                The reference pin says that it is sending around 9.3 V into the TPS. I'm assuming that's too much, unless this is how high the older cars should be reading. I guess that I'll need to take it to a shop and have them evaluate the ECM?

                Comment

                  #9
                  check reference voltage to other sensors and see if they're better than 5v
                  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

                    #10
                    I think the reference voltage is all from the same supply internally. The MAP sensor would be the other easy to get to sensor to check. If it is showing the same voltage... then definitely the ECM.

                    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
                    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

                    Originally posted by gadget73
                    ... and it should all work like magic and unicorns and stuff.

                    Originally posted by dmccaig
                    Overhead, some poor bastards are flying in airplanes.

                    Comment

                      #11
                      EEC3 runs a 9 volt reference signal, not 5 volts like EEC4. I don't know the proper idle position voltage on that system, but its probably not 1 volt.
                      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

                        #12
                        in that case... the reference signal is probably fine and the ECM is OK.

                        The hesitation may be due to the cryptic EGR system on those things. I know nothing about those but there's been a few threads on here about them.

                        Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
                        rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

                        Originally posted by gadget73
                        ... and it should all work like magic and unicorns and stuff.

                        Originally posted by dmccaig
                        Overhead, some poor bastards are flying in airplanes.

                        Comment

                          #13
                          Thanks for the help! I ran through a bunch of threads and it sounds like I need to keep plunking away at the issue. I've found a lot of people saying that the ECM is a component that either 'works or doesn't work; there's no in between', so that's a relief. I think I need to: 1) check out the MAP sensor; 2) check all of the vacuum lines; and 3) check the fuel pressure coming from the pump. When I replaced the spark plugs it looks like the engine is running a little lean, but then again, Gadget74 said in one of his posts that the EEC3 system typically runs lean. Slymer, how would I go about checking the EGR system? I'm not even sure on where to start with that.

                          Comment

                            #14
                            The EGR system is really no different than other models, but it is a little more inclined to clog. Do you have the iron or the aluminum intake? The EGR system differs slightly on them. On the iron intake, you can remove the CFI unit and the EGR spacer underneath it. Take the EGR valve and it's cooler off the spacer and make sure you chisel out all the carbon crud in there. Clear out the ports in the intake itself as best you can too and see if helps any when it goes back together. If its the aluminum intake, there is no spacer that can be removed. Just pull the EGR valve off and clean the ports in the intake as best you can. There is a cooler that may or may not bolt between the EGR valve and the intake. If its there, make sure it is also not packed full of junk.

                            What sort of shape are your vacuum lines in? They really need to be perfect for this to work right. Ideally, I'd say replace every one of them but at a minimum, they need a very close inspection for any cracks or signs of leaks.

                            As for the idle voltage thing, thinking about it this may be one of those systems that needs the idle voltage to be something specific in order to work right. Unfortunately I just don't know what that voltage may be. If anyone has the Ford manuals specifically for the 83, that ought to have the info. Its possibly in some EEC-specific or emissions controls manual though.
                            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

                              #15
                              The intake is iron, and I have not performed a thorough inspection of the vacuum lines. They look decent after doing a quick assessment, but I will take a weekend and tackle both the EGR and vacuum lines (hopefully before it snows here in Denver). Another factor I have not mentioned is that this Marquis only has 30,000 miles on it... an older couple owned it, and kept it covered IN their garage. So the interior and body are in cherry shape, but I'm sure a period of rest that long may have dried out some gaskets and vacuum lines. I just checked the new spark plug wires tonight with a tester while it was running to make sure there was no issue with the distributor, and they all seem to be firing correctly. Also, about a month ago, the I checked the timing and it was correct as well.

                              Comment

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