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  1. #1
    Jr. Engineer JTWard's Avatar
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    Question Frustrating cold idle problem ?

    I have a 1990 Chevy 1500 Silverado, 305 w/ TBI injection. New Injectors, fuel pump & tank & filter. Idle is way too low when started, So I installed a new "Idle Air Control Module" but it made little difference. Last month I had some electrical problems that wound up being a bad EPCM and we installed a new EPCM and calpak chip. But no matter what I do, I can't find this low Idle gremlins. I've looked for a vacuum leak but I can't find it and the EPCM doesn't leave any trouble codes as I have check five times now. I'm out of ideas now ???? Thank you !

  2. #2

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    Have you took off the throttle body and actually cleaned it out?...run some sea foam through your brake booster vaccum line and see if that helps also...maybe it will help clean the gunk out and idle better

    2009 Chevrolet Silverado 1500 LT Z71 Crew Cab "All-Star Edition"

    Line-X'd Bed
    Line-X'd Custom Brush Guard(Heavy Duty)
    5.3L Flex Fuel
    275/65R18 Toyo Open Country AT2's
    2" Rough Country Leveling Kit(want to get the 2.5 RC kit)
    EGR In-Channel Vent Visors
    Exterior PLUS Package
    Interior PLUS Package
    K&N Drop-In Air Filter
    ProFlaps
    Cat-Back Dual Exhaust
    Black Bowties
    Diablo Sport Predator(AFM Disabled)
    ProFlaps
    Towing Mirrors
    Next Planned Mods
    Blacked out Tail Lights
    Aftermarket Rims

  3. #3
    Jr. Engineer JTWard's Avatar
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    well everything we've found so far shows a clean, non sludge engine internals. When we put new head gaskets on everything was spotless ? We've cleaned everything we've touched so far, But I can't figure out this last nagging idle problem. I'm going to try squirting a little carb cleaner around the engines intake manifold to see if I can locate a vacuum leak ? Thank you !

  4. #4

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    Ya it does kinda sound your getting a small vaccum leak...those are the worst ones to find!

  5. #5
    Jr. Engineer JTWard's Avatar
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    Well even shooting carb cleaner around the intake manifold might work, But I'm doubtful as we just install new gaskets when we did the head gaskets last year. It doesn't leak and fluids, so if there is a flaw or crack, and I'm not saying there is, it sure is hiding pretty well.

  6. #6

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    sounds more like you might be a little "fat" typically a small vac leak would increase idle. try adding propane through throttle body,idle up its lean, down its rich. don't forget MAP & MAF sensors. i' don't remember if they put MAF on the 90's but a dirty MAF will cause idle issues. also don't know anything about the "chip" but any time you "tweak" a PCM you are asking for ghosts to appear.

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