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  1. #1

    Default Rebuilt 454 running bad

    Hey guys!

    My uncle and I finally got the 454 back in the dually. He went to crank it up to warm the engine, and it would die after 5ish minutes of idling. He thought it was the alternator was not working, but when I put my meter on the battery, voltage when the motor was running was 13.5 volts, so it isn't the alternator. When I was testing his theory about the bad alternator, I revved it up to about 1500 rpm, and it ran nice, but when I let off the accelerator, it tried to idle, but couldn't keep a steady idle speed and died. Now it won't idle for anything :| . Anyone have any ideas as to what's going on? I'm thinking it may be the IAC (idle air controller, or something like that), but he keeps asking me if that was the problem, why isn't it throwing a code. As far as I know, the IAC isn't electronic, is it? Also, the motor is throwing a P1345 code, which is CKP and CMP sensor correlation code. From what my grandfather is saying, there is a learn process for that that has to be performed while driving. Both of the offending sensors were changed before putting the motor back in the truck. Any merit to what my grandfather said? We would drive it and attempt the relarn procedure, except that my uncle didn't put the torque converter back in in preparation to drop the tranny to get it rebuilt. Any fresh ideas are always appreciated. Thanks guys!
    Last edited by Crawdaddy; 08-13-2007 at 07:34 AM. Reason: fixed title

    1991 Chevy Suburban 1/2 ton 2WD w/ chevy SBC 350-3/4 ton drivetrain upgrade w/4.10 gears 200K miles
    2005 Saturn ION-2 Stock 277K miles
    1982 Bronco, 1993 Bronco (sold), 1971 M35A2 Deuce and a Half

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  2. #2
    TrailLeadr's Avatar
    Join Date
    Jun 2005
    Coventry, Rhode Island


    I don't think the learning portion would have anything to do with the idle. The learning is usually just for the trans.
    IAC runs about $49.99 over at

    check out this guy's suggestion on how to test the IAC
    Rhode Island

  3. #3


    If you are getting the code about cam/crank correlation, your distributor is off a tooth or so. Correcting this may get your idle back.

    99 K 1500 Suburban
    78 Silverado Big 10 w/factory 454
    00 S-10 Blazer
    1976 Trans Am
    1980 Honda CB900 Custom

  4. #4
    Jr. Mechanic
    Join Date
    Jul 2007
    Washington State, the Dry Side ( Southeastern)


    Quote Originally Posted by GaryL View Post
    If you are getting the code about cam/crank correlation, your distributor is off a tooth or so. Correcting this may get your idle back.
    Actually...I was thinking the same thing....However I was not sure if you rebuilt the engine....I was thinking the timing chain maybe off a few teeth....The distributer is much easier to check....But you should check TDC in #1 just to make sure you have Cam timing.

    My Thoughts.....
    Just Another Day in Paradise...

  5. #5
    Jr. Apprentice CaJuN625's Avatar
    Join Date
    Aug 2007
    Pleasant View, UT

    Default Dumb mode

    Unplug the computer and put the engine in "dumb" / "open loop" / "limp" mode. If it idles nice, it's a sensor giving a reading outside what the computer knows what to do with or is telling the computer to do something it shouldn't be. If it doesn't change the way the engine runs, it's something off in the timing - maybe the bolt's loose that holds the distributor from rotating?

    If it idled ok for 5 minutes ... you may have had oil supply or coolant supply issues and could have done some damage.
    Pleasant View, UT

    1998 Tahoe LT 4dr 4wd
    2004 GMC 2500HD CC / SB

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