5.7 TBI timing: cold-start issues

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by themaddhatter, Sep 7, 2004.

  1. themaddhatter

    themaddhatter Registered Member

    Apr 16, 2002
    Likes Received:
    91 5.7 suburban TBI.
    When I start it after it hasn't run for 5 hours or more, the engine starts and chugs along like the timing is wrong. After about 30-60 sec, it smoothes out the timing (computer does it I am assuming) and it runs fine. If you start it up within an hour or two of it doing this, it starts and runs normal. It is as if the computer forgets where it is set on the baseline. I just checked the baseline timing with the black/tan wire disconnected, and it is right on at 0. This engine has had in the last year: new plugs/coil/cap/rotor/distributor, so that shouldn't be the culprit (hopefully).

    Any ideas? Is there a battery or something associated with the computer that remembers this timing position that discharges after a few hours?

    Any help would be appreciated,

  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

    Dec 14, 2001
    Likes Received:
    Pleasanton, CA.
    I would put money on a fuel filter bad. The fuel filter should have a drainback valve in it and it may be bad enough that fuel pressure is bleeding off and causing your initial idle problem. This is just my educated guess. /forums/images/graemlins/thumb.gif

    When is the last time you changed the fuel filter?
    Also check for any fuel leaks that could be small enough the allow air to enter the fuel stream and give you an air pocket at start-up.

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