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  1. #1

    Default poor idling and hard start on s10 blazer

    so my girlfriends s10 blazer with 4x4 was running really rough lately and has been starting hard even after installing a new starter and battery and spark plugs. Well pulled the codes today and it got: running too rich and something with the egr valve? So they said it could be either O2 sensor or egr valve anyones thoughts suggestions? If i replace the O2 sensor and egr valve do you think it will fix the hard start and poor idle? and lookslike O2 sensor will be easy to replace, infront or behind cat but no idea about egr valve. Thanks everyone

    2000 Chevy Silverado 2500 4x4

    6.0L v8:great: 4L80E

    2.5 in Daystar leveling keys

    285/75/16s BFG ATs on HD wheels

    Cab lights and tool box

  2. #2
    Jr. Engineer hundojoe's Avatar
    Join Date
    Feb 2010
    Elk River, Minnesota


    It might be the fuel pressure regulator, does the truck get parked inside? does the garage smell like gas after it sits over night? if so prolly the fuel pressure regulator. Also if you pull the vacume line off the the fuel pressure reguater and raw fuel comes out of the regulator that means the rubber diaphram inside has deteroiated. And is more then likely the culprit.

  3. #3
    Legend kgibson181's Avatar
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    Jul 2009
    Cedar Grove, NC
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    I had the same exact problem with my truck, rough, low idle, hard to start, and sometimes shut off. The culprit in mine turned out to be the idle control valve. Took it off and the tiny gap the valve has in its released position for idle was completely clogged with gunk. 1 bottle of throttle body cleaner and 20 minutes later my truck ran like new. May not be the problem with your blazer but hey its worth a shot before spending money on replacing sensors.

    2003 Silverado 1500
    V8 4.8L 294ci
    2 inch Pro Comp Leveling Kit
    3 inch Rough Country Lift
    33 inch Nitto Terra Grapplers
    5% Tint All Around
    2 12" Kenwoods

  4. #4


    If it runs good but doesn't want to idle, and you have an EGR code, I'd bet there is carbon in the EGR valve. This could also show the O2 reading off. It is real common on the 4.3L Blazers. My '93 Jimmy used to do it after a long run on a highway. First stop light it sounds like it was gonna die but barely idles.

    The EGR is supposed to close at idle and the design is such that a chunk of carbon keeps it from closing. It is an electromagnet operated plunger shaped like a hockey puck on the front of the intake just above the water pump. It connects two openings built into the manifold and the plunger seals one @ idle.

    I 'cured' it once w/ a can of Seafoam poured slowly into the brake booster vacuum hose at a fast idle but it came back.

    There is a electrical plug & two 10 mm bolts and a metal gasket so it is easy to remove. I found a carbon ring built up around the plunger and used a tiny screwdriver to break it up and shake the carbon out. I also sprayed it w/ carb cleaner to get it all out. Cured the problem.

    This came up often on the S-10 boards too!
    Still Loyal to GM after all these years...:shocked:
    2006 Impala LT 3.5L
    2005 Silverado WT small cab/longbed 4x4 4.3L V6
    1999 Grand Am 3.4L in TX w/ our youngest
    1993 GMC Jimmy 4.3L 4 door 4x4 'Ole Rusty' - 'SOLD'
    1988 S-10 small cab/longbed HT3.4L Crate Engine
    1970 Nova 250 I-6, factory 3 sp floor shifter.
    1968 Chevelle 'Nomad' Wagon 250 I-6 w/ 3 on da' tree.

  5. #5
    murdog94's Avatar
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    Feb 2008
    Cloquet, Minnesota, United States
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    Also when was the last time the Cap and rotor were changed.. MY 310K mile S-10 Blazer has gone thru both a new cap and rotor with a similar problem to yours, and it then ate the FPR went out and it ran really bad after that.


    1997 Chevy S-10 Blazer 4X4 with 330K miles and counting (Hunting rig).

    2009 Saturn Aura XE (wifes car)

    2011 F-150 Crew 4X4

    "Hold it to the floor till you see God.... Then Brake!!!!"

  6. #6


    okay thank you for all your suggestions im going to look into all those now, if it was the fuel pressure regulator would the pressure jump alot them if i put a pressure gauge on it? and where is the idle control valve located. And murdog im not sure the last time the cap was replaced but i will look at it tonight as well its only got 120k on it so ill check it out

  7. #7
    murdog94's Avatar
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    Feb 2008
    Cloquet, Minnesota, United States
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    You will go thru a cap basically yearly.. They corrode very fast. the IAC is on the throttle body mounted on the right side if i remeber. And the Fuel pressure might not jump up and down. Mine didnt it just leaked when there was pressure at the regulator.

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