'94 Concours starts at run away engine speed
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, '94 Concours starts at run away engine speed in Past Cadillac Vehicle Discussion; I just installed a new fuel pump on my 1994 Concours, started and ran like a new car. I then ...
  1. #1
    Mark Hollis is offline Cadillac Owners Member
    Automobile(s): 1994 DeVille Concours
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    '94 Concours starts at run away engine speed

    I just installed a new fuel pump on my 1994 Concours, started and ran like a new car. I then remembered that I hadn't seen a vacuum hose on the top of the fuel pressure regulator. I removed the top cover to expose the fuel pressure regulator and there wasn't a vacuum line on top of the regulator.
    While I was away from the car for a few minutes, my Dad started the car then immediately turned the car off as it started as if the accelerator pedal was on the floorboard of the car. After explaining why the car shouldn't have been started, we put the cover back on, yet the car will continually start as if the accelerator pedal is on the floor, yet the position of the pedal is all the way up as it should be.
    I can also hear something "sucking" air near the Mass Airflow when the key is first turned on, but will stop when the fuel pump stops running. Any ideas?

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: '94 Concours starts at run away engine speed

    There is no vacuum line involved on the '93/'94 because the FPR is inside the manifold and subjected to manifold vacuum.

    If it is still running away at high RPM, you still have a massive vacuum leak. Find that sucking air noise and you'll have found your problem. Something was not reinstalled properly.

  4. #3
    amunderdog is offline Cadillac Owners Connoisseur
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    Re: '94 Concours starts at run away engine speed

    you will need to smoke the intake to find the leak as running it is not an option.

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: '94 Concours starts at run away engine speed

    Spraying Brakleen around the manifold and any other potential leak points will also work.

  6. #5
    Mark Hollis is offline Cadillac Owners Member
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    Re: '94 Concours starts at run away engine speed

    Thanks for the information, it is most appreciated more than each of you know.
    Here is what I discovered today. It turns out that what I thought was a "sucking air" sound was actually one of the fuel injectors had jumped out of its place and was sitting off to the side, spewing fuel. I also discovered that the seal on the bottom of the injector missing and so far there is no sign of it anywhere. The engine has Sorensen injectors and the seal is bright green in color so I would think it would be easy to find. Since I am having to lift some of the injectors to see in the area, I am going to install a new seal and o-ring set and pray that this solves everything.

  7. #6
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: '94 Concours starts at run away engine speed

    Quote Originally Posted by Mark Hollis View Post
    It turns out that what I thought was a "sucking air" sound was actually one of the fuel injectors had jumped out of its place and was sitting off to the side, spewing fuel.


    EDIT:
    Just realized that this a is a '94 so the injector is inside of the manifold. Not quite as bad as if it where a later year.

  8. #7
    Mark Hollis is offline Cadillac Owners Member
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    Re: '94 Concours starts at run away engine speed

    Thanks again for all the help...will post the results and see what happens.

  9. #8
    Mark Hollis is offline Cadillac Owners Member
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    Re: '94 Concours starts at run away engine speed

    UPDATE!!!
    After searching, the fuel rail injector kit was completely unavailable, I settled for going to a salvage yard and buying an injector with the seal as well as a few other seals that I was allowed to pull. This seated well and took care of the sucking air issue as well.
    But, the starting at full throttle issue remains. I have hit the accelerator after starting the car to no avail. The engine sounds great, other than a full throttle start.
    I am searching for a vacuum leak, loose wire, or something with the throttle that may be stuck, but so far, have found nothing.
    I have pulled the codes, and there are no new codes, just codes in history. I am also thinking about buying a scanner that will work on this car.
    Any suggestions?

  10. #9
    Aztec ETC ECS's Avatar
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    Re: '94 Concours starts at run away engine speed

    Quote Originally Posted by Ranger View Post
    Something was not reinstalled properly.
    Like the cover?
    It ran fine until removal, right?

  11. #10
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    Re: '94 Concours starts at run away engine speed

    Manifold cover would be my first guess as well.

  12. #11
    Mark Hollis is offline Cadillac Owners Member
    Automobile(s): 1994 DeVille Concours
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    Re: '94 Concours starts at run away engine speed

    Thanks for the information, will give it another go.

  13. #12
    Mark Hollis is offline Cadillac Owners Member
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    Re: '94 Concours starts at run away engine speed

    You guys are great!!! The cover was installed wrong, with the "Northstar" nameplate being slightly offset, and two of the bolts in the wrong places. Test drives, the car did well.

    On a longer test drive of about 20 miles open highway, I began to notice the accelerator pedal leaving my foot slightly, then return to my foot, but no change in the performance. After stopping with the car turned off for about 30 minutes, I started the car without issue, and drove another 5 miles, when the accelerator began to leave my foot again, with slightly more travel.

    I pulled into a parking lot and the car started to run a little rougher, and turned the car off for about 30 min. Restarted the car, while idling, the accelerator pedal would go down a short bit then a click could be heard, and the accelerator pedal would return to the full up position like it was searching for an idle. The engine would barely run while trying to idle, yet when I would accelerate, the car would run a bit better, enough to make a short trip to a place I could safely leave the car. On this part of the drive, I accelerated more then I normally would, and the car ran fairly well. After the car cooled completely, I could drive the car the 20 miles home, with the accelerator pedal leaving my foot again ever so slightly.

    Thinking I may have damaged the fuel pressure regulator, I replaced the regulator, the car started better and ran better than it has in a long time. I did another test drive at highway speeds, curvy back roads with a lot of hills, enough to put the car through various accelerations, and slowing to idle speeds. The car ran great. Upon returning home, I shut the car off, restarting after a few minutes, and we are back to searching for an idle and running rough.

    The idle speed control motor was replaced about 45k miles ago as well as the PCM.

    Any ideas?

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