Question about 1993 Jeep Grand Cherokee

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93 jeep GC Rough idle, difficult start, but drives smooth

The main problem I have is the rough idle. When I stop at a light, it almost stalls, and occasionally does, unless I keep one foot on the gas and one on the brake. The other problem is the difficulty starting it up. It usually takes a few times before it finally starts up. And when it does, some smoke comes out from under the hood (around the throttle body and air filter area). But it clears out quickly. Only happens on startup. No other time
I've changed out the idle air control valve, which was filthy and stuck most of the way out. Changed the fuel filter which was also disgusting. The fuel that came out was almost black. Doing those two things has shown noticeable improvement, but the idle is still rougher than it should be, and the startup is still difficult.
When it's not at an idle it runs very smooth. no hiccups, no nothing.

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  • Steve
    Steve Sep 11, 2009

    what is an egr? and where is located?

    Thank you!

  • Steve
    Steve Sep 11, 2009

    Excellent advice. Seems like something I could handle, and would be a cheap fix.

    Thank you!

  • Steve
    Steve Sep 11, 2009

    cool. any tricks to checking for vacuum leaks?

  • Steve
    Steve Sep 13, 2009

    I pulled the throttle body off and cleaned it out real good. and you were right that thing was absolutely filthy.
    i put it back on and it seems to run about the same, maybe a little better. I'll continue to look for leaks and run some fuel injector cleaner and such through it.

    thanks for all your help! i don't know what i would do without people like you volunteering your knowledge.
    Big Thanks!



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Sounds to me like you still have issues with fuel delivery, you amy have a throttle body that is filthy inside, old fuel will leave a varnish that will gum up fuel and air passages inside causing rich and or lean conditions which is more than likely the cause of you rough idle and hard start up conditions, it is best to remove and disassemble the throttlebody unit and clean it very thoroughly, reinstall it and the base gasket, then use a fuel additive and a fuel stasbilizer like stabil that will remove any water you might have in your fuel...

Posted on Sep 11, 2009

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  • Jeff Phillips
    Jeff Phillips Sep 11, 2009

    Also you may want to check for vacuum leaks around the intake, throttle body and any vacuum hoses in the system, a vacuum leak will cause a lean misfire at idle known as a lean idle misfire...


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Sounds like the egr is stuck/plugged. remove when engine is cold & soak with throttle body cleaner. also could be a vacuum leak check the pvc valve & the line going to the brake booster. This is normal solutions to the 4.0l

Posted on Sep 11, 2009

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You have a bad spark plug it shows a code what cylinder is

Posted on Sep 11, 2009

Testimonial: "Awesome. I haven't tried that yet. I'll change em all and report back. Thank you!"

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