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so my 98 ls1 idles at about 1025 when warm.

This is a discussion on so my 98 ls1 idles at about 1025 when warm. within the General Help forums, part of the LSx Technical Help Section category; and idles up to 12-13oo when cold, it's an M6 and i feel this is not right. Any ideas, suggestions, ...

  1. #1
    Member goof4080's Avatar
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    so my 98 ls1 idles at about 1025 when warm.

    and idles up to 12-13oo when cold, it's an M6 and i feel this is not right.
    Any ideas, suggestions, help?

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    NY Representative basballny2's Avatar
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    try cleaning your maf.....my m6 idles around 1000 until it warms up then goes down to about 750-800.....i dont think your too far off but 1300 is a little high, try the maf and let us know if it gets better.....have you recently installed any mods on the car?

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    Moderator Cutlass's Avatar
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    check your PCV hose for vacuum leaks. Thats what it was on my car

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    Member goof4080's Avatar
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    cleaned the maf about a month ago. only mods drivetrain mods are catback, volant and mild tune, but the idle was the same before and after that. i'll have to check the pcv.

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    Member goof4080's Avatar
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    now i read somewhere the 98 ls1's did not have an adjustable idle screw but the 99+ did? i think mine has a hex nut screw for the idle stopscrew, if i can't find leaks should f with this? and is this stock for a 98?

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    NY Representative basballny2's Avatar
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    i dno if they had an idle adjust screw on the tb or not in 98 but you can play around with it, just turn it a little at a time and see if it helps but if your car just started doing it thats not the solution to your problem

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    Member goof4080's Avatar
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    Quote Originally Posted by basballny2 View Post
    i dno if they had an idle adjust screw on the tb or not in 98 but you can play around with it, just turn it a little at a time and see if it helps but if your car just started doing it thats not the solution to your problem
    it's done this since i bought it a year ago, i just never thought it was abnormal until i started noticing some posts about this lately. i'll have to fiddle and see what i come up with. where's the pcv and common fault points... cracks in the hose, clogged valve, etc?

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    Moderator Cutlass's Avatar
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    mine leaked right here but your 98 PCV system looks a little bit different.

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    Moderator Cutlass's Avatar
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    98 LS1 PCV configuration


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    Member goof4080's Avatar
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    Quote Originally Posted by Cutlass View Post
    98 LS1 PCV configuration
    awesome thanks!.

    so this looks to be a pain to replace all the hosing, let alone even check it. theoretically can i remove it, plug it and just put a breather in the oil fill?

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    Member goof4080's Avatar
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    Quote Originally Posted by Cutlass View Post
    mine leaked right here but your 98 PCV system looks a little bit different.
    Click for full size
    here my car has a small cream colored plastic tube/hose about half that dia, and thick foam covering that plugs into the intake mani. does it just pull out of the mani, i may be being too gentle.
    and my pcv valve is located halfway down the pass valve cover.
    Last edited by goof4080; 06-26-2010 at 03:10 PM.

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    Moderator Cutlass's Avatar
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    I'd like to suggest the LS6 PCV conversion with a catch can






  13. #13
    Member goof4080's Avatar
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    update:
    we tried to find a vacuum leak around the engine bay, basically spraying a lot of brake cleaner trying to get it to stumble. no luck. when revved and then releasing the pedal, the rpms hang up for a second then slowly fall back down. still idling at 1200, then down to 1000. and only seems to go down to 1000 when the car is at 0mph only. if it's moving and the car is out of gear it idles at 1200 until i come to a complete stop.
    we unplugged the TPS and when revving it got it to briefly drop down to 850ish then it would pop back up to 1000.

    could a bad tps do this?
    a dirty throttle body?
    are the HVAC controls vacuum controlled or electronic?

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    Member goof4080's Avatar
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    ok so did some further sleuthing this weekend.
    tried to find a vacuum leak around the top of the motor, basically sprayed a bunch of brakecleaner to try at get it to stumble. no dice.

    basically when revved, the motor hangs and then drops down to 1200 and then 1000 when at 0 mph. when rolling and out of gear, the idle does not drop below 1200 until i come to a complete stop.

    played with tps. when disconnected at revved, we actually got it to dip down to 850 temporarirly and then it went back up to 1000.

    hopefully this gives some people some ideas.

    are the HVAC controls on these 4th gens(mine is a 98) vacuum controlled?
    when

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    Member goof4080's Avatar
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    oops double post, i thought i lost the first one.

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    Moderator Cutlass's Avatar
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    Although I've never tried it, I've heard of this procedure to reset the TP sensor to read 0% at idle. But if the TB blade is open to far it won't reset (ie idle screw open to far or dirty blade holding the TB open)
    Reset the TPS: turn key off, unplug TPS (round 3 pin connector), turn key to run (not start) and wait about 10 seconds, turn key off, plug TPS connector back in. It will reset at next key-on.

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