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Poor Idle on 3800-II

This is a discussion on Poor Idle on 3800-II within the General Help forums, part of the LSx Technical Help Section category; Car in question is a 1996 Camaro V6 with the 3800-II motor. When I first start it, it revs up ...

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    Moderator 35th-ANV-SS's Avatar
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    Poor Idle on 3800-II

    Car in question is a 1996 Camaro V6 with the 3800-II motor.

    When I first start it, it revs up to about 2200RPM and stays there for a few seconds and the idles down to roughly 1200RPM and stays steady.

    Once it has been running about 30 seconds or so, it begins to idle erratic. The idle will go from 800 (almost dies here) to 2000RPM....and continues to do this.

    If I rev it up and let my foot off the gas, it will also stay at that RPM for several seconds before coming back down.

    The SES light is on. I pulled 3 codes.

    P0171 (System too lean, left bank on 4 sensor systems)
    P0174 (System too lean, right bank)
    P0300 (Engine misfire detected).

    I've tried cleaning the MAF and that made no difference. My next thought is possibly a vacuum leak and this is causing the idle problem also?

    Thanks for any input. I don't drive this car hardly at all and am just trying to soak as little as possible before I try to sell it come spring time. Oh, and the car has 209,000 miles on it! Car drives fine other than the idling.

    JM

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    None Shall Pass Knight's Avatar
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    Could be vacuum leak, possibly O2 sensors if you've got them. Off chance it could even be bad gas depending on if you store it or just filled it somewhere - has happened to me a couple of times.
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    Senior Member tatertot91's Avatar
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    Is that thing still alive

    Check your coils

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    Wouldn't coils cause a too rich code?

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    Sounds like a vacuum leak or something has broken or loosened up and is allowing unmetered air into the engine. Do they have Idle Air Control valves or anything like that?

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    Veteran 0rion's Avatar
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    I'm guessing a vacuum leak somewhere....check hoses and intake gaskets.

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    The 3800-II only has 3 vac hoses (not sure on the 96) could be one but doubtfull. Have you checked to be sure your PCV still rattles? Also check your fuel vapor purge solenoid (will not throw a code if bad) for proper operation. Then there's always the digi EGR.. A bad MAP may cause this too..
    Last edited by Smittro; 02-21-2010 at 05:08 PM.
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    Moderator 35th-ANV-SS's Avatar
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    Quote Originally Posted by Smittro View Post
    The 3800-II only has 3 vac hoses (not sure on the 96) could be one but doubtfull. Have you checked to be sure your PCV still rattles? Also check your fuel vapor purge solenoid (will not throw a code if bad) for proper operation. Then there's always the digi EGR.. A bad MAP may cause this too..
    I did pull the PCV and cleaned it. She still rattled and wasn't too gunked up.

    Looks like it probably is a vacuum leak from all the responses. I'm going to be pulling hoses and checking them as soon as the weather gets a little warmer. The car sounds like it's got a big choppy cam in it when it's at idle.

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    Senior Member tatertot91's Avatar
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    Quote Originally Posted by Knight View Post
    Wouldn't coils cause a too rich code?

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    Moderator 35th-ANV-SS's Avatar
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    Quote Originally Posted by pajeff02 View Post
    Sounds like a vacuum leak or something has broken or loosened up and is allowing unmetered air into the engine. Do they have Idle Air Control valves or anything like that?
    There is an air idle control valve. I haven't replaced that ever.

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    Quote Originally Posted by 35th-ANV-SS View Post
    There is an air idle control valve. I haven't replaced that ever.
    Pull it off and look inside the hole for carbon build up. The pintle may not be seating the whole way if the opening onside is gummed up.

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    Quote Originally Posted by 35th-ANV-SS View Post
    I did pull the PCV and cleaned it. She still rattled and wasn't too gunked up.

    Looks like it probably is a vacuum leak from all the responses. I'm going to be pulling hoses and checking them as soon as the weather gets a little warmer. The car sounds like it's got a big choppy cam in it when it's at idle.
    If you think it is a vac leak have her smoked see if smoke comes out somewhere..

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    Quote Originally Posted by Smittro View Post
    If you think it is a vac leak have her smoked see if smoke comes out somewhere..
    My neighbor owns his own mechanic shop. I might just see if he can do that for me. That would be the quickest way to pin point it. Thanks.

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    Moderator Cutlass's Avatar
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    Yep high idle and lean codes on both banks is almost definitely a vacuum leak

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    Quote Originally Posted by Cutlass View Post
    Yep high idle and lean codes on both banks is almost definitely a vacuum leak
    You know now that you guys keep mentioning it.. If the car sits outside for long periods of time and do'nt move rodents like mice/chipmunks tend to make camp in a vehicle and they will chew any plastic or rubber. Not to mention there's always dry rot too.

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    Moderator 35th-ANV-SS's Avatar
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    Thanks for all the responses and feedback. I'll be looking into it this weekend. I'll let you know what I find.

    Steven - It had been sitting outside for the longest time before I pulled it into the garage. I wouldn't be surprised it the hose going to the back of the intake is rotted.

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    Quote Originally Posted by 35th-ANV-SS View Post
    Thanks for all the responses and feedback. I'll be looking into it this weekend. I'll let you know what I find.

    Steven - It had been sitting outside for the longest time before I pulled it into the garage. I wouldn't be surprised it the hose going to the back of the intake is rotted.
    Could be a posibility, mine has a hard line from the MAP to the fuel reg, my rubber ends were hard as a rock and needed replaced. Good luck J..

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    OK so I've been busy as all hell and the car hadn't been a priority......BUT...I finally looked at it this morning.

    Found 2 things wrong.

    1st is..YES..a vacuum leak. The intake is leaking. When I spray it along the entire fuel rail the engine idle changes. So I'm confident that the intake needs to come off and the gasket replaced.

    2nd thing is the check valve on the fuel pump is bad. Not really too worried about this, but once I turn the car off the fuel pressure drops slowly and when I go to start it, it takes a few turns before it starts so I'm guessing this is why it is doing this. Taking time for the fuel to get back up front.

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    Senior Member tatertot91's Avatar
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    It's still running

    At least you're getting closer at solving the problem. Before you try and start it just turn the key once or twice before to prime the system.

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    Hey V6 Doc....

    Any tips on getting the intake out? I know you just took yours out to paint it so I thought I would ask while still fresh in your mind.

    I have the air duct out, the throttle body off, serpentine belt off....now I'm trying to get the fawking alternator out. Not budging. I have a Hayne's manual I am using, but it's pretty much useless in my eyes.

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