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    #1

    engine hesitation

    Hi. Newbie here, first post. I have a '91 Grand Marquis w/ the 5.0L fuel injected engine and AOD tranny. I am experiencing engine hesitation/jerking when at part throttle maintaining speed. The jerking/hesitation is most noticeable while maintaining speed anywhere btwn 35 to 45 MPH. I do not notice the problem if I use cruise control at 60 MPH. My car accelerates fine with no hesitation/jerking. My TPS read 1.4V and I was able to modify/adjust it to 1.1V before I cracked the side of it w/ a drill bit. I replaced the TPS and now have a reading of 1.25V. I'm a little nervous about modifying the new TPS. The engine idles smooth and fine. I removed the screen mesh filter element below the PCV valve which was pretty caked w/ carbon build up. I checked the gap in my spark plugs and have them all adjusted btwn .48-.52. Being that the car accelerates fine I feel certain I can rule out anything distributor/plug wire related. I don't know if maybe the cause could be a transmission TV cable adjustment or what. I was hoping by replacing the TPS and double checking my spark plug gaps that it would solve the problem but it persists. I removed the upper intake manifold while I was replacing my heater hoses and noticed that it has some pretty bad carbon deposits. The hesitation occurs when the engine has reached full operating temp and it doesn't matter if it is in overdrive or not. The car doesn't get driven a whole lot, only when I go home to visit my mother. Any ideas or suggestion on what I can try next? Sorry for the long post, but I wanted to provide as much info as possible.

    Matt
    Tags: None
    #2
    try pulling and plugging the green line to the EGR valve on the side of the throttle body. If the hesitation goes away, my bet is the EGR regulator is sticky and not regulating properly. If no change, its not that.

    Oh, have you replaced the fuel filter in recent memory? If not, do that.
    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

      #3
      The fuel filter was replaced about a year ago and the EGR valve was replaced about 6 months ago. Could a loose TV cable cause these symptoms? When I removed and re-installed the upper intake I noticed that the TV cable was loose when I re-installed the throttle bracket. I don't recall if the TV cable was tight prior to me removing the upper intake. I have upgraded to the brass bushing.

      Comment

        #4
        Not likely. The TV cable being out of adjustment will mostly make the shift points too early. It won't cause the engine to hesitate or misfire.

        The EGR valve itself is seldom at fault. the regulator upstream of it that actually makes it open and close is what goes wonky. Unhooking the EGR valve will determine if the hesitation is related to the valve opening. I had similar problems on my car and after some 2 years of occasional attempts at diagnosis, I found the problem was the regulator solenoid. Instead of giving variable levels of vacuum, it was all or nothing. I shot some WD40 into the regulator which un-stuck it and the problem went away.
        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 gadget73 View Post
          Not likely. The TV cable being out of adjustment will mostly make the shift points too early. It won't cause the engine to hesitate or misfire.

          The EGR valve itself is seldom at fault. the regulator upstream of it that actually makes it open and close is what goes wonky. Unhooking the EGR valve will determine if the hesitation is related to the valve opening. I had similar problems on my car and after some 2 years of occasional attempts at diagnosis, I found the problem was the regulator solenoid. Instead of giving variable levels of vacuum, it was all or nothing. I shot some WD40 into the regulator which un-stuck it and the problem went away.
          This could very well be my issue as well I have replaced the solenoid but it may be sticking there is always the occasional new bad part.
          2002 Mercury Grand Marquis LSE, Sylvania Zevo LED Headlights, MSD Blaster Coils, K&N Cold Air Intake, Dual Exhaust, 3.27's - Dally Driver

          1983 Lincoln Continental Mark VI, Smog Delete - Summer Cruiser

          ​

          Comment

            #6
            ok, thanks Gadget73. Are you talking about the EGR valve sensor when you say regulator? Yeah, I don't have any problems w/ the AOD shifting. What are your thoughts about the TPS? I have read on other forums saying that the TPS voltage should be down around .98V-.99V. The lowest reading I can get w/ my TPS is 1.2 something volts.

            Comment

              #7
              Mercurygm88, What kind of driveability problems are you experiencing?

              Comment

                #8
                Originally posted by MattDoscher View Post
                Mercurygm88, What kind of driveability problems are you experiencing?
                A slight hesitation when cruising a constant speed between 60-70 miles an hour and also between 35-45. I replaced the egr solenoid and all was fine for a couple of days and then it started happening again which is why I think thats what it may be. Everything else is new as well.

                heres the thread I started on it.

                65mph+ miss - GrandMarq.NET - Panther Headquarters
                http://www.grandmarq.net/vb/showthread.php?45715-65mph-miss&highlight=
                The meat and potatoes of GMN-Discussions related to the 5.0/5.8 engine.
                2002 Mercury Grand Marquis LSE, Sylvania Zevo LED Headlights, MSD Blaster Coils, K&N Cold Air Intake, Dual Exhaust, 3.27's - Dally Driver

                1983 Lincoln Continental Mark VI, Smog Delete - Summer Cruiser

                ​

                Comment

                  #9
                  the egr regulator I think means the egr solenoid at the other end of the vacuum line on the passenger inner fender.

                  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

                    #10
                    Originally posted by slymer View Post
                    the egr regulator I think means the egr solenoid at the other end of the vacuum line on the passenger inner fender.
                    yep that thing little black thing with two vacuum lines and plug. The position sensor is the thing bolted to the back of the valve.
                    2002 Mercury Grand Marquis LSE, Sylvania Zevo LED Headlights, MSD Blaster Coils, K&N Cold Air Intake, Dual Exhaust, 3.27's - Dally Driver

                    1983 Lincoln Continental Mark VI, Smog Delete - Summer Cruiser

                    ​

                    Comment

                      #11
                      Is the regulator even available? Haven't even seen an aftermaket one. I am talking about the black unit with the cap and the foam filter under it.


                      "Hope and dignity are two things NO ONE can take away from you - you have to relinquish them on your own" Miamibob

                      "NEVER trade your passion for glory"!! Sal "the Bard" (Dear Old Dad!)

                      "Cars are for driving - PERIOD! I DON'T TEXT, TWEET OR TWERK!!!!"

                      Comment

                        #12
                        Originally posted by miamibob View Post
                        Is the regulator even available? Haven't even seen an aftermaket one. I am talking about the black unit with the cap and the foam filter under it.
                        yeah I got a borg warner one from oreilly auto parts they had I think 3 different brands available and could even get me a motorcraft one for like $75. I think the borg warner one I got was $35. Autozone and NAPA auto parts also have them available in there store brands.
                        2002 Mercury Grand Marquis LSE, Sylvania Zevo LED Headlights, MSD Blaster Coils, K&N Cold Air Intake, Dual Exhaust, 3.27's - Dally Driver

                        1983 Lincoln Continental Mark VI, Smog Delete - Summer Cruiser

                        ​

                        Comment

                          #13
                          I had this exact problem and it went away when I replaced my TFI module to fix a no spark issue. I really don't know why, but it did.

                          Comment

                            #14
                            On the 91, the regulator is hanging right behind the throttle body if I'm not mistaken. All 3 solenoids ought to be there. The EGR one is the one with a red and a green line. Just disconnect the EGR valve first to see if anything changes. No point in replacing the regulator if its not actually bad. It may not be this at all. Unhooking the valve is just a way to pinpoint if the issues are related to the EGR system or not.

                            And for what its worth, I bought a new one directly from Ford, though my old one was working just fine after spraying some wd40 in it. Increasingly I'm leery of aftermarket EFI related parts. They seem to cause more trouble than they fix.
                            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
                              Thanks everyone for chiming in. It's interesting to read. I will have to try what gadget73 recommended and disconnect the EGR regulator the next time I'm in SC. Me and mercurygm88 seem to be having the same problem as what he describes is what I'm experiencing, hesitation at part throttle while maintaining speed. I noticed that when I drove it a few weeks ago and had the cruise on at 60 there was no hesitation. It only seems to happen when driving by foot. I also notice a hesitation when slowly opening the throttle from a stop, but if I depress the accelerator more than I normally would there is no hesitation. What do you all think about my TPS not reading .98V-.99V and reading 1.2ishV?

                              Comment

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