Fast idle control valve or switching to carberator
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5.0 and 5.7 Discussion, Fast idle control valve or switching to carberator in Cadillac Engine Technical Discussion; I have my Cadillac 77 seville with the 5.7 liter that i'm getting worked on because of the fuel pumps. ...
  1. #1
    Nico143 is offline Cadillac Owners Member
    Automobile(s): 1977 Cadillac Seville
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    Fast idle control valve or switching to carberator

    I have my Cadillac 77 seville with the 5.7 liter that i'm getting worked on because of the fuel pumps. but in fixing and replacing the fuel pumps, there was a surge that supposively blew the ECM, replace the ECM, sparks, tune up and the mech is telling me that i need to replace the idle control valve because the engine is not getting the right mix and it's idling rough. He also recommend to switch to a carbuerator. Is it necessary to do a conversion like that or am I being taken to the cleaners?

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  3. #2
    Nico143 is offline Cadillac Owners Member
    Automobile(s): 1977 Cadillac Seville
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    Exclamation Re: Fast idle control valve or switching to carberator

    Quote Originally Posted by Nico143 View Post
    I have my Cadillac 77 seville with the 5.7 liter that i'm getting worked on because of the fuel pumps. but in fixing and replacing the fuel pumps, there was a surge that supposively blew the ECM, replace the ECM, sparks, tune up and the mech is telling me that i need to replace the idle control valve because the engine is not getting the right mix and it's idling rough. He also recommend to switch to a carbuerator. Is it necessary to do a conversion like that or am I being taken to the cleaners?
    Seem like after all that the mechanic didn't replace the wires or the harness (stupid) so now my option is going carborator...does anyone have the specs on doing that so I can get the parts and get this ride going?

  4. #3
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Fast idle control valve or switching to carberator

    I see those idle control valves quite often on Ebay lately. I replaced my fuel injection with a carb because the fuel injection wasn't dependable enough for me. All my fuel injection problems were electrical related; electric connections were corroded and had intermittent stalling issues to diagnose on the side of the road. With the carb I only have to open the hood to change the oil. If you have new fuel pumps and a new ECM then you might as well try to keep the original fuel injection going and check Ebay for a idle control valve. Good luck.

  5. #4
    hcaddy95's Avatar
    hcaddy95 is offline Cadillac Owners Fanatic
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    Re: Fast idle control valve or switching to carberator


  6. #5
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
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    Re: Fast idle control valve or switching to carberator

    The old Olds 350 computer was a real dinosaur, from what I remember many many dealers put them back to carbs. I would, or go with a more modern EFI like a TBI from a 93 350 Chevy.

    Don't feel back going back to carb on this one!

    Honestly, they never were right.

  7. #6
    Nico143 is offline Cadillac Owners Member
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    Re: Fast idle control valve or switching to carberator

    Quote Originally Posted by cadillac_al View Post
    I see those idle control valves quite often on Ebay lately. I replaced my fuel injection with a carb because the fuel injection wasn't dependable enough for me. All my fuel injection problems were electrical related; electric connections were corroded and had intermittent stalling issuesto diagnose on the side of the road. With the carb I only have to open the hood to change the oil. If you have new fuel pumps and a new ECM then you might as well try to keep the original fuel injection going and check Ebay for a idle control valve. Good luck.

    I have the stalling issue now. I could drive for about 4-6 miles and then it want to act like it's not getting gas. i pull over and cut off the car wait five minutes and then it will be fine. what would you think is causing this?

  8. #7
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Fast idle control valve or switching to carberator

    You are going to have to invest in a fuel pressure gauge at some point. If the pump in the tank was replaced then the tank and inlet sock filter should be fairly clean. Mine had a damaged/spliced wire (green I think) going to fuel tank that used to lose connection. Sometimes I would wiggle the wires on the ECM and it would start. How is the idle speed cold and warm? Does it idle smooth? My old FI used to idle super smooth. It took a little while to get my carb to run and idle that smooth.

  9. #8
    carnut is offline Cadillac Owners Master
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    Re: Fast idle control valve or switching to carberator

    The fast idle valve ( called a choke heater back in its day ) has nothing to do with idle smoothness unless its staying fully extended. All it did was raise up in the throttle body when the engine was cold causing a large vacuum leak which the computer read as more air and added more fuel to raise the idle until the car was fully warmed up. The 2 wire connector to it supplied voltage to heat the wax within it which, once heated, would allow the valve to drop or sink down into the throttle body lowering the idle speed. Remove the air cleaner lid with the engine running and fully warmed up. Press on the heater and it should have NO spring tension. If you can push it down and the idle is affected, its faulty or the little brass lever on its side has broken off and wont activate the micro switch to heat the valve. Assuming the valve is fully seated the idle air rate can be adjusted at the front of the throttle body by the large screw in the bottom center. Early cars used an allen wrench screw with a jamb nut, later ones simply had a large screw with a spring behind it. That screw can correct a rough idle.

  10. #9
    SSG
    SSG is offline Cadillac Owners Member
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    Re: Fast idle control valve or switching to carberator

    Quote Originally Posted by Nico143 View Post
    I have the stalling issue now. I could drive for about 4-6 miles and then it want to act like it's not getting gas. i pull over and cut off the car wait five minutes and then it will be fine. what would you think is causing this?
    How long is it fine for??? 4-6 more miles or can you drive all day? Give a little more detail as to what happens. Be careful if you push down on the air control valve. You can latch the valve closed as it has two wire like clips that will get stuck under the end of the plastic cylinder it moves in. You won't have fast idle on start up if that happens.

  11. #10
    SSG
    SSG is offline Cadillac Owners Member
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    Re: Fast idle control valve or switching to carberator

    Quote Originally Posted by Nico143 View Post
    I have my Cadillac 77 seville with the 5.7 liter that i'm getting worked on because of the fuel pumps. but in fixing and replacing the fuel pumps, there was a surge that supposively blew the ECM, replace the ECM, sparks, tune up and the mech is telling me that i need to replace the idle control valve because the engine is not getting the right mix and it's idling rough. He also recommend to switch to a carbuerator. Is it necessary to do a conversion like that or am I being taken to the cleaners?

    Your being taken to the cleaners. Find an old Caddy mechanic that "WORKED" on the Fuel Injection systems back then. Not just someone who worked on Caddys. The injectors fired the four outer cylinders and then the four inner injectors. Many times the ECU would fail on one set of injectors. That would give you a rough idle and low power.

  12. #11
    TOMMY MILAN is offline Cadillac Owners Member
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    Re: Fast idle control valve or switching to carberator

    Quote Originally Posted by cadillac_al View Post
    I see those idle control valves quite often on Ebay lately. I replaced my fuel injection with a carb because the fuel injection wasn't dependable enough for me. All my fuel injection problems were electrical related; electric connections were corroded and had intermittent stalling issues to diagnose on the side of the road. With the carb I only have to open the hood to change the oil. If you have new fuel pumps and a new ECM then you might as well try to keep the original fuel injection going and check Ebay for a idle control valve. Good luck.
    I have a 79 Seville...can you give me details on what is needed to do I carb conversion to replace EFI? Thanx//tommy milan

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