Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

TBI: "high idle problem"

Discussion in 'The Garage' started by conoverbandit, Feb 6, 2004.

  1. conoverbandit

    conoverbandit 1/2 ton status

    Joined:
    Jan 23, 2002
    Posts:
    452
    Likes Received:
    0
    Location:
    Conover N.C
    TBI: \"high idle problem\"

    Hello,

    I got a 87 chevy r-30 pickup, has TBI 454 init. The problem I have is a "high idle" type thing, the engine act's as if it has a choke onit and it's hung up. I have driven it as a trial and error thing. The "choke" light comes on in the dash-----not sure what this is all about I did'nt think TBI had a choke. It's weird the choke light will come on for a minute or do, go off and it will idle down to normal, start driving again and light comes on again and idle goes back up. Here's what I have tried so far: I have replaced the TBI heater to intake gasket, replaced the TBI to heater gasket, complete tune up plugs,wires, cap/button, ran the vac.lines from tbi to thier hook ups, done vac. test on them.....found 2 leaking going to a small black box ,from box to egr, replaced both and found A.I.R line disconnected. changed coolant sensor (thought this would fix gauge also but gauge in dash cluster still not working). This is what I know about this engine: it sat for over a year, then was started, backfired and burnt the TBI connectors up.I replaced those but I did drive the truck home with the burnt ones. I have also cleaned the idle air control valve and reinstalled it. All of this has helped engine run better but it still will not idle. At this point I'm thinking rebuild TBI and 2 new injectors since I figure they might have been damaged in the backfire incident. Can Y'all help me? This is my first big block truck, and it's beginning to get to me. Thanks,

    Conoverbandit
     
  2. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Re: TBI: \"high idle problem\"

    Hmm, I'm not sure what (or why!) the choke light is doing there... /forums/images/graemlins/confused.gif

    But for this:
    [ QUOTE ]
    changed coolant sensor (thought this would fix gauge also but gauge in dash cluster still not working).

    [/ QUOTE ]
    Which coolant sensor did you replace? TBI trucks have two. One in the drivers side head that feeds the gauge in the dash and one in the intake manifold that feeds the ECM for help in determining fuel needs.
     
  3. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Re: TBI: \"high idle problem\"

    Do you see the Check Engine light come on when you first start the truck? I'm wondering if somehow the wrong insert is in the dash and that the Choke light really should be labeled Check Engine...
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,979
    Likes Received:
    189
    Location:
    Roy WA
    Re: TBI: \"high idle problem\"

    Yeah, the Choke and Check Engine Light "filter" is the exact same piece, (same location in the cluster) just different printing on it.

    Either the filter could have been changed, or it's the wrong cluster for the truck would be my suspicion.
     
  5. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

    Joined:
    Jan 21, 2001
    Posts:
    20,716
    Likes Received:
    2
    Location:
    Undisclosed Location
    Re: TBI: \"high idle problem\"

    Possible vacuum leak?
     
  6. conoverbandit

    conoverbandit 1/2 ton status

    Joined:
    Jan 23, 2002
    Posts:
    452
    Likes Received:
    0
    Location:
    Conover N.C
    Re: TBI: \"high idle problem\"

    Thanks for all the replies so far,

    I did not know there were 2 coolant sensors.However I did change the one in the intake, so I guess that one goes to ecm? and no "check engine light" when ignition is on or running or anything. best I can tell it is orginal cluster, everything else works except temp and clock.Don't know if there is any connection between the 2 but temp and clock are side by side each other. You know where about's that 2nd coolant senser is in the head? I have found 2 wires laying in engine compartment, 1 has insulation? around it about 8 inches up the wire, the other is just a plain wire but both have the same type connecter in them. Which is you know the older type sensers that the wire just slid over top of the senser? both of these have that same connector on them, and they run up each side of the engine. The one on the pass. side actually exits the harness that runs along the intake(this is the one with insulation on it) But I can't see any other sensers from looking down each side of the engine either.Is the 2nd. senser under the exhaust manifold somewhere? Sorry to be long winded just trying to give as much info as possible to aid in help dianosing problem. THanks
     
  7. Jonny-K5

    Jonny-K5 1/2 ton status

    Joined:
    May 27, 2003
    Posts:
    1,654
    Likes Received:
    0
    Location:
    SoCal
    Re: TBI: \"high idle problem\"

    [ QUOTE ]
    Possible vacuum leak?

    [/ QUOTE ]

    i second that, i had a high idle problem, leaky vacuum hose.
     
  8. conoverbandit

    conoverbandit 1/2 ton status

    Joined:
    Jan 23, 2002
    Posts:
    452
    Likes Received:
    0
    Location:
    Conover N.C
    Re: TBI: \"high idle problem\"

    Hello,

    Where do you think the leak would be? I have vac. tested all lines comming from the TBI it's self to thier connections, took each piece off and vac. tested it, found 2 bad lines and replaced them.Everything I've done so far has helped the engine, when I first got it there was a loud "hissing" sound comming from it, but when I checked the fuses and found one labeled "gauges/idle" it was blown, so I replaced it with same type/size fuse..This is when the gauges (except clock and temp) started working again. Also the hissing noise went away, as posted above I changed both TBI gaskets,I was told this was a common problem on this set up.Thank you for your time,
     
  9. conoverbandit

    conoverbandit 1/2 ton status

    Joined:
    Jan 23, 2002
    Posts:
    452
    Likes Received:
    0
    Location:
    Conover N.C
    Re: TBI: \"high idle problem\"

    Just to let you know, I did find the second coolant senser.No wires hooked to it. Found wire and connected.Have'nt tried it yet, but hopefully this will fix problem w/gauge. Thanks,
     
  10. bigyellowjimmy

    bigyellowjimmy 1/2 ton status

    Joined:
    Jan 15, 2004
    Posts:
    2,105
    Likes Received:
    0
    Location:
    Chandler, AZ
    Re: TBI: \"high idle problem\"

    First check ECM codes.....but sounds to me like a vacuum leak, must have been a decent fire to burn up the the FI connectors so could be something on/near the TB. Since you've covered all vac hoses check gasket from TB to intake and also the throttle shaft, see if it has up/dn play. If its bad enough it'll leak vac or the plates will stick inside like you are pushing on the accelerator. Next, look down the TB with a flashlight while engine is running, is there an even fuel spray or clobs or big drops of fuel? Also check all vac sources threaded into the intake for leakage, especially going to the brake booster. Good luck, keep us informed on your progress! /forums/images/graemlins/thumb.gif
     
  11. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Re: TBI: \"high idle problem\"

    found several vacdk leaks on my 88 454. The heaer gaskets were bad but I see you replaced those. I also found cracks in all those plastic vac lines.
     
  12. conoverbandit

    conoverbandit 1/2 ton status

    Joined:
    Jan 23, 2002
    Posts:
    452
    Likes Received:
    0
    Location:
    Conover N.C
    Re: TBI: \"high idle problem\"

    Yea, I hate those plastic lines. I can't understand why they (gm) went to this, every vehicle I touch that has those usually break while I'm trying to unhook them or move them around to get to something else. /forums/images/graemlins/rotfl.gif
     
  13. conoverbandit

    conoverbandit 1/2 ton status

    Joined:
    Jan 23, 2002
    Posts:
    452
    Likes Received:
    0
    Location:
    Conover N.C
    Re: TBI: \"high idle problem\"

    This truck has hydroboost. I thought those only came on diesel engine set ups but this puppy's got it, double checked the emission decal and it says 7.4 (454)?
    Like I stated earlier, you don't need any extra light to see the fuel going down into this thing, she's flooding to a point. At any time while the engine is running you can see the fuel "standing" on top of the butterflies.....maybe a puddle in each bore aboutt he thickness of a matchbook! If I leave the air cleaner off the fuel jumps out onto the intake! Maybe I'll get one of these days lol. Thanks for the replies so far, they have helped alot.Let's keep going with the ideas and hopefully I can get this thing fixed and start driving on a regular basis. /forums/images/graemlins/thumb.gif
     

Share This Page