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Suburban running rough at idle

This is a discussion on Suburban running rough at idle within the Technical / Maintenance forums, part of the General Discussion category; Hello I'm new to the forum. I have a 1990 Suburban with a 350 and it's a 4x4 with 160,000 ...

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    Suburban running rough at idle


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    Hello I'm new to the forum. I have a 1990 Suburban with a 350 and it's a 4x4 with 160,000 miles on it. It's running rough at idle. I have replaced the Egr, Egr sole, new dist., new wires, new plugs, new temp sen., new idle air control, new o2 sen. I have checked for vac leaks. When I replaced all of these it ran fine for about 4 days, then started again. Any help would been great. Thanks

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    Registered User Bruce Wayne's Avatar
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    Re: Suburban running rough at idle

    My 1993 suburban was running really rough at idle and while driving a month or so ago. How recently was your fuel filter replaced? it could be clogged, or the fuel pump could be going bad, or the sock in the gas tank could be clogged up as well. Mine had a bad injector and that might be worth looking into also.
    Hope this helps...
    I would replace the filter if it hasnt been replaced for a while and cut the old one open to see if it was clogged up. You should be able to hear the fuel pump working if you stick your head under the gas tank while it is running.
    1997 6.5 K1500
    6 inch RCX/35 inch BFG's/18 inch Moto Metal MO962

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    Re: Suburban running rough at idle

    Thank you for getting back to me. I did replace the fuel filter about six months ago. I was hoping that the pump wasn't bad, but worried now it might be my problem. I heard about the sock in the tank is that something you have to replace also? I have bought the injectors, haven't put them yet. Thanks for the help.
    Quote Originally Posted by Bruce Wayne View Post
    My 1993 suburban was running really rough at idle and while driving a month or so ago. How recently was your fuel filter replaced? it could be clogged, or the fuel pump could be going bad, or the sock in the gas tank could be clogged up as well. Mine had a bad injector and that might be worth looking into also.
    Hope this helps...
    I would replace the filter if it hasnt been replaced for a while and cut the old one open to see if it was clogged up. You should be able to hear the fuel pump working if you stick your head under the gas tank while it is running.

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    Registered User Bruce Wayne's Avatar
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    Re: Suburban running rough at idle

    Yeah for sure, you might think about just taking it to a good mechanic who can probably find the problem in an hour or so instead of putting all this time and parts into it. I like to figure out my own stuff too and just like you i replaced a bunch of solenoids, my fuel pump and sock, fuel filter, etc. before i took it to a mechanic who did the job in a day. But good mechanics arent always that easy to find... All the stuff your replacing is probably good to replace anyways if they're getting old.
    The sock filter is something you should replace whenever you put in a new fuel pump. The fuel pump is kind of a pain to replace thogh it took me a good three days so you should be sure its bad before you do it. And your pump doesnt sound like its bad if ilthe suburban runs semi-well... But like i said you should be able to hear a strong constant humming noise from the tank while the burb is idling.
    Last edited by Bruce Wayne; 07-27-2012 at 10:03 PM.
    1997 6.5 K1500
    6 inch RCX/35 inch BFG's/18 inch Moto Metal MO962

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    Re: Suburban running rough at idle

    Yeah a good mechanic is almost impossible around here. It's all about the bottom line service look here is about 130 not to mention the time they want keep it. Talking about dealerships. I believe something is wrong with the fuel pump. I think that will be my next deal. Thank you for all your help with this. How's yours doing now? I also think that everything I've replaced needed it. Hopefully that will buy me some more time with this engine. I going to replace it, when I rebuild the truck.

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    Resident Dick Quyonmob's Avatar
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    Re: Suburban running rough at idle

    Test fuel pressure 9-12psi is factory spec.

    Cap and rotor? TBIs can eat cap and rotors.

    Check distrbutor shaft for play, common for TBI motors to show wear on the dizzy drive gear.

    Timing? Disconnect the advance wire (not sure on the colour of the wire on square bodies), base timing with advance disconnected should be 0-2'.

 

 

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