'94 SLS Idling to fast
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Northstar Engines and System Technical Discussion Discussion, '94 SLS Idling to fast in Cadillac Engine Technical Discussion; Hi, My '94 SLS is Idling way to fast, around 1800 rpm. I changed out the idle speed motor, with ...
  1. #1
    Reactor is offline Cadillac Owners Member
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    '94 SLS Idling to fast

    Hi,
    My '94 SLS is Idling way to fast, around 1800 rpm. I changed out the idle speed motor, with no effect on the problem, I checked the vacuum lines, they look ok.
    any suggestions?

    thanks for your help.

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  3. #2
    wydopnthrtl's Avatar
    wydopnthrtl is offline Cadillac Owners Fanatic
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    Re: '94 SLS Idling to fast

    Is the throttle body clean? (blade not closing all the way)

    Generally if you have a high idle and can't find it.. it's usually a vacuume leak somewhere.

    Rich

  4. #3
    Reactor is offline Cadillac Owners Member
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    Re: '94 SLS Idling to fast

    I will check it to see, also, I will check the intake cover for leaks, that is one spot I did not check.
    thanks

  5. #4
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: '94 SLS Idling to fast

    Check around the top of the throttle body on the vacuum line "boot". That seems to be a common problem place

  6. #5
    Reactor is offline Cadillac Owners Member
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    Re: '94 SLS Idling to fast

    Vacuum line boot? would that be the location where the 2 vacuum line tubes come out?
    also, would one of the green rubber seals around one injector being half gone cause this problem?

  7. #6
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: '94 SLS Idling to fast

    Yes, and maybe.

    I think because the injector is inside the manifold, that the lower seal doesn't really seal anything. But I would get it replaced anyways, they're cheap.

  8. #7
    Reactor is offline Cadillac Owners Member
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    Re: '94 SLS Idling to fast

    I pulled off the top of the intake, all looked ok, then I re-installed the top and still it idles to fast.
    I checked the vacuum lines at the top of the throttle body, they were ok, and I went ahead and checked any vacuum lines I could find, still idles to fast.
    Could a bad Fuel Pressure Regulator cause this?
    Fuel pressure seems to be about 45psi, and the needle is solid steady, with the car running, not pulsing up and down.
    does this indicate a bad FPR?
    again thanks for the help.

  9. #8
    Ranger's Avatar
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    Re: '94 SLS Idling to fast

    Does not sound like a bad FPR, but why didn't you check it when you had the cover off? Sounds more like a vacuum leak (maybe around the cover), sticky throttle plate or a bad ISC motor (I think the '94 used the ISC motor).

  10. #9
    Reactor is offline Cadillac Owners Member
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    Re: '94 SLS Idling to fast

    How do you check the FPR with the cover off?
    throttle plate looks normal, but I did not look at it close, I will re-check it.
    I replaced the ISC motor, and it did not help.
    ?
    I might have to take it to a pro.

  11. #10
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    Re: '94 SLS Idling to fast

    With the cover off, turn the key on to pressurize the fuel system, but DO NOT start the engine as it will run away WOT and bounce off the rev limiter. Now look for fuel leaking from the FPR nipple. There should be none.

    Did you adjust the ISC motor after replacement?

  12. #11
    Reactor is offline Cadillac Owners Member
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    Re: '94 SLS Idling to fast

    I set the ISC to the same distance as the old, but it is more likely set shorter, which is pushing on the throttle less.

  13. #12
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    Re: '94 SLS Idling to fast

    But did you use the correct proceedure to set it? You have to push on the plunger with your thumb. The plunger will retract. When it bottoms out, pull the plug and adjust it to .030 gap with the throttle linkage, then plug it back in.

  14. #13
    Reactor is offline Cadillac Owners Member
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    Re: '94 SLS Idling to fast

    I guess I did not use the correct procedure, I will re-check that adjustment.
    thanks.
    I checked the FPR with the cover off, and it was ok.
    still idling to fast after the cover was put back on.

  15. #14
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: '94 SLS Idling to fast

    Have you checked for codes? You might have some sensor problem causing the engine to idle higher than it should. TPS comes to mind.

  16. #15
    Reactor is offline Cadillac Owners Member
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    Re: '94 SLS Idling to fast

    I read the codes through the instrument display after holding down the OFF and warmer buttons at the same time until it went into the test mode.

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