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Rough start, low MPG

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  • Rough start, low MPG

    Ok, I have searched around the forums but have not found a problem quite like what I have.

    to start, I have an 91 EFI 5spd all stock. Car here: W4RKRYs 91 Build

    It was getting hard to start a few months ago. If the car was driven, shut off, then started again with the engine warm, I would have to crank it for 20 seconds with the accelerator pinned. It would only fire on 2 cylinders, slowly gaining rpm until about 5k rpm then suddenly all the cylinders would fire and it would be fine.
    Later, it would take up to 30 or 40 seconds to finally fire all the cylinders.
    I replaced the stock fuel filter, was super dirty, but did not help. Car does this to this day.

    I will post a poor quality starting video link as soon as it is uploaded to youtube.

    Then, just about a week and a half ago, My milage has dropped considerably, down to almost 23 or so mpg. The check engine light will come on at random times then turn off. Doesnt matter if its hot, cold, driving fast or slow, it just comes on randomly. When I go to check the codes, there are none stored. I checked plugs and wires, they were ok, disty looks fine, etc.
    I used a stethoscope to listen to the injectors, they appear fine as well.
    Checked o2 sensor voltage, it swings from .85 to .19, so it seems ok.
    I know they are switching to winter gas, but I would not expect this drastic of a drop in MPG.

    I have not done a compression test, but I assume it is bad, this thing burns an obscene amount of oil, but it has always done that, never had MPG problems before.
    Will Samet

    JDMSTIVA - Rest in Peace. Festiva of the Month, May '16 - Best Beater & Bad Luck Award, FMX - (Build Thread)

    JDMSTIVA V2 - Racecar, Showcar, Work in Progress - (Build Thread)

    1990 LX - B6D swapped, mostly stock.

    How to find me:
    Facebook messenger is the best way. m.me/willsamet
    Feel free to PM me anytime!
    Reddit / Snapchat / everywhere else: w4rky
    Instagram/Twitter: @WILLSAMET

  • #2
    Clogged cat? or maybe clogged injectors. I'd run some fuel injector cleaner in the gas tank to eliminate that possibility.

    The oil burning may have clogged up the cat after all this time.

    Also pull the coil wire, and look for corrosion in the coil.
    Last edited by TominMO; 10-28-2015, 10:14 PM.
    90 Festy (Larry)--B6M (Matt D. modified B6 head), header, 5-speed, Capri XR2 front brakes, many other little mods
    09 Kia Rondo--a Festy on steroids!

    You can avoid reality, but you can't avoid the consequences of avoiding reality--Ayn Rand

    Disaster preparedness

    Tragedy and Hope.....Infowars.com.....The Drudge Report.....Founding Fathers.info

    Think for yourself.....question all authority.....re-evaluate everything you think you know. Red-pill yourself!

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    • #3
      Tom, I have no cat, And the injectors sounded like they were working with the stethoscope. Could they be making the right sounds but still be plugged?
      Will Samet

      JDMSTIVA - Rest in Peace. Festiva of the Month, May '16 - Best Beater & Bad Luck Award, FMX - (Build Thread)

      JDMSTIVA V2 - Racecar, Showcar, Work in Progress - (Build Thread)

      1990 LX - B6D swapped, mostly stock.

      How to find me:
      Facebook messenger is the best way. m.me/willsamet
      Feel free to PM me anytime!
      Reddit / Snapchat / everywhere else: w4rky
      Instagram/Twitter: @WILLSAMET

      Comment


      • #4
        Originally posted by w4rkry View Post
        Tom, I have no cat, And the injectors sounded like they were working with the stethoscope. Could they be making the right sounds but still be plugged?
        IDK, maybe. Can't hurt to use the cleaner. I pretty much do it with every new-to-me car.

        In my experience, we take a ~10% hit in MPG in the winter.
        Last edited by TominMO; 10-28-2015, 10:19 PM.
        90 Festy (Larry)--B6M (Matt D. modified B6 head), header, 5-speed, Capri XR2 front brakes, many other little mods
        09 Kia Rondo--a Festy on steroids!

        You can avoid reality, but you can't avoid the consequences of avoiding reality--Ayn Rand

        Disaster preparedness

        Tragedy and Hope.....Infowars.com.....The Drudge Report.....Founding Fathers.info

        Think for yourself.....question all authority.....re-evaluate everything you think you know. Red-pill yourself!

        Comment


        • #5
          Not plugged but maybe sticking open, leaking and dribbling. This will wash oil off cylinder walls and flood the engine with the fuel left in the rail after shut down. Extended throttle open cranks to clear the fuel and oil. You may have gone from leaking squirting which will require lots of fuel to run.

          Get the dirt out of the tank, flush the system, change the filter again, and get the rail cleaned out and the injectors ultrasonically cleaned, checked for balance and spray pattern or just get new ones.

          Double check what you told us and look for the problems..other things can cause these things too.
          Reflex paint by Langeman...Lifted...Tow Rig

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          • #6
            Can the injectors be cleaned while in the engine (with seafoam or similar) or will I need to remove them?
            Will Samet

            JDMSTIVA - Rest in Peace. Festiva of the Month, May '16 - Best Beater & Bad Luck Award, FMX - (Build Thread)

            JDMSTIVA V2 - Racecar, Showcar, Work in Progress - (Build Thread)

            1990 LX - B6D swapped, mostly stock.

            How to find me:
            Facebook messenger is the best way. m.me/willsamet
            Feel free to PM me anytime!
            Reddit / Snapchat / everywhere else: w4rky
            Instagram/Twitter: @WILLSAMET

            Comment


            • #7
              VIDEO: https://www.youtube.com/watch?v=eWaS...nnel=WillSamet
              Will Samet

              JDMSTIVA - Rest in Peace. Festiva of the Month, May '16 - Best Beater & Bad Luck Award, FMX - (Build Thread)

              JDMSTIVA V2 - Racecar, Showcar, Work in Progress - (Build Thread)

              1990 LX - B6D swapped, mostly stock.

              How to find me:
              Facebook messenger is the best way. m.me/willsamet
              Feel free to PM me anytime!
              Reddit / Snapchat / everywhere else: w4rky
              Instagram/Twitter: @WILLSAMET

              Comment


              • #8
                Chemical cleaning can remove carbon - petroleum based deposits, Ultra sound will remove oxidisation such as corrosion or rust. It depends what is causing the sticking..if it is sticking a injector. One of the other things is a fuel pressure regulator leaking back through the vacuum hose. Look for signs, clues..
                Reflex paint by Langeman...Lifted...Tow Rig

                Comment


                • #9
                  Yes, the injector tips can plug and the injecter will still open and close. Try a heavy dose of injector cleaner in your tank and if it doesnt help after half a tank or so then remove the injectors and visually inspect them.
                  Hows your spark plug gap? I forgot about mine once and the gap got so big the one cylinder wouldnt fire untill it got hot enough to self ignite basically. Check your wires, are they grounding out? How about your cap and rotor? The rotor and inside the cap can get very corroded up. Has oil ever fouled your plugs?
                  Check your vaf.
                  Your distributor hasnt come loose and turned to put the timing off?
                  Coil is still good?
                  When your check engine light comes on IMMEDIATLY turn the car off and coast with it off to the side of the road and check the code.


                  Sent from my iPhone using Tapatalk

                  Comment


                  • #10
                    Havent checked the gap, plugs were ok last I checked, Wires and rotor are all new or newer. Havent check the vaf or coil. I will check them and the injectors tomorrow
                    Will Samet

                    JDMSTIVA - Rest in Peace. Festiva of the Month, May '16 - Best Beater & Bad Luck Award, FMX - (Build Thread)

                    JDMSTIVA V2 - Racecar, Showcar, Work in Progress - (Build Thread)

                    1990 LX - B6D swapped, mostly stock.

                    How to find me:
                    Facebook messenger is the best way. m.me/willsamet
                    Feel free to PM me anytime!
                    Reddit / Snapchat / everywhere else: w4rky
                    Instagram/Twitter: @WILLSAMET

                    Comment


                    • #11
                      I just realized I never posted the solution to my Problem.

                      It ended up being a bad ECT. It was not reading anything properly, causing the ECU to default to some crazy rich fuel maps even when the engine was warm. After replacing the sensor, it fixed the issues!
                      Will Samet

                      JDMSTIVA - Rest in Peace. Festiva of the Month, May '16 - Best Beater & Bad Luck Award, FMX - (Build Thread)

                      JDMSTIVA V2 - Racecar, Showcar, Work in Progress - (Build Thread)

                      1990 LX - B6D swapped, mostly stock.

                      How to find me:
                      Facebook messenger is the best way. m.me/willsamet
                      Feel free to PM me anytime!
                      Reddit / Snapchat / everywhere else: w4rky
                      Instagram/Twitter: @WILLSAMET

                      Comment


                      • #12
                        Originally posted by w4rkry View Post
                        I just realized I never posted the solution to my Problem.

                        It ended up being a bad ECT. It was not reading anything properly, causing the ECU to default to some crazy rich fuel maps even when the engine was warm. After replacing the sensor, it fixed the issues!
                        I had no idea a bad ECT could cause that! I don't even know where my b6t gets its coolant temp reading from.
                        Dark blue '91 B6t + E series
                        Something new breaks every day

                        Comment


                        • #13
                          It was probably pinned to -40* ...
                          Trees aren't kind to me...

                          currently: 2 88Ls (Scrappy and Jersey), 88LX, 90L(Pepe), 91L, 91GL (Skippy) 93 GL Sport (the Mighty Favakk), 94 (Bruce) & 95 Aspire SEs, 97 Aspire (The Joker),
                          94 Justy 4WD, 87 Fiero GT, plus 2 parts cars. That's my fleet.

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