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  1. #1
    Sr. Engineer
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    Default Engine rough at ilde or cruising speed

    Hey guys
    '91 Chevy Silverado, 5.7L V8 w/ TBI (Edelbrock Manifold).

    The engine "lopes", struggles, sputters at idle speeds or at a cruising speed.
    If I press the throttle, it is fine......just when I level off at a running speed or if I am at a stop light idling.

    I have check the fuel filter, and he appears fine, I can blow through him.

    I just looked at the TBI and sprayed some cleaner on him. Both injectors are spraying fuel.

    My vacuum hoses appear to be fine, I have the hose going into the EGR plugged, so he is out of the picture.


    Is there anything else I can check and try.
    I will prolly replace the plugs and wires.....I did see some rust on the #1 spot of the distributor cap, as well as some rust dust in the spark plug wire boot connecting to him....so I will sand down the tips there.

  2. #2
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    murdog94's Avatar
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    Default

    I would install a new cap and rotor as well those are the most common problems with these trucks. Then clean the IAC as well and check to make sure that it is good.. Also is the Check engine light on??
    Mike

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  3. #3
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    The CEL only has come on once, and that was while approaching a stop light.

    ---------- Post added at 06:24 PM ---------- Previous post was at 06:15 PM ----------

    The other thing of note, not sure if it has anything to do w/ it.....

    But I believe my A/C compressor is going bad or getting ready to lock up......so I was trying to add in more PAG Oil to the compressor....Engine and A/C on.

    While I was doing this, it was really bogging down the engine (Compressor I think is shot cause it makes awful noises)......it eventually shut off.
    But since then, this sluggish, sputtering symptom has been prevalent....
    It has been noticeable since the A/C Compressor has been acting up.....but it has gotten worse since the above incident.

  4. #4
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    Another question

    Regarding the problem A/C Compressor....if this thing is getting to the point where it might be locking up.
    Is it possible for that thing to throw the timing on the engine?
    Since it is one serpentine belt (I would think no....worst case it would shred the belt)......

  5. #5

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    anybody mension timing yet...??????

    ---------- Post added at 10:13 PM ---------- Previous post was at 10:10 PM ----------

    Quote Originally Posted by MightyMax View Post
    Another question

    Regarding the problem A/C Compressor....if this thing is getting to the point where it might be locking up.
    Is it possible for that thing to throw the timing on the engine?
    Since it is one serpentine belt (I would think no....worst case it would shred the belt)......
    NO, can not affect timing and can not lock up if its off...the clutch will be free spinning if off and if it locks up in on the belt would be squeeeeeeling like hell.

    1996 Suburban K3500 SLT DUALLY
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  6. #6
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    I am thinking maybe timing as well.
    It seems to be more noticeable when the engine is warm/hot.
    Not happening when the engine is cold.

    I went out this morning and cleaned the distributor cap....so I cleaned the corrosion off the contacts (all 8 ) inside the cap, and I cleaned off the #1 tip going to the #1 spark plug wire. There was rust on him....the other tips were fine.

    Took him for a test drive and was fine while cold, but started happening again when it warmed up.

    I am thinking maybe fuel pump....but I will see if I can get a timing light and check him....that will be the easier of the two at this point.

  7. #7
    Jr. Engineer hundojoe's Avatar
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    Default

    The original motor in my 1989 chevy had similar symptoms, ended up being a worn cam, stabbed a new cam and lifters and ran great after that.
    1999 Silverado Regular Cab Short Box
    Black on Black, Line-X sprayed in bed liner
    5.3 with K&N CAI, Texas Speed 220/220 cam with 112 deg LSA
    Texas Speed computer Tune
    American Racing Headers with Cats
    4.11 gears front and back, with Eaton rear posi
    Flowmaster 40series true duals
    16X8 American Racing Nitros with 305/70/16 Goodyear MTR's
    285's in the pic



    If it ain't broke...........Give me a minute!

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  8. #8
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    I replaced the spark plug wires....the problem didn't seem to be as bad...I think I will need to take it for a longer road trip.

    But I think it is the fuel pump, so I am gonna try and replace him in the next few days.

  9. #9
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    I changed the fuel pump out yesterday (man that sucked)....
    The problem is still there.....I guess I need to start checking sensors??

  10. #10
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    I am beginning to think the Idle Air Control (IAC) valve......
    How big a deal is he to change out???
    Can it be done quick?


    Also, what about the ECM, what am I looking at for doing a replacement on him?

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