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Thread: Stable Idle

  1. #1
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    Question Stable Idle

    Background

    I've been trying to tune my 2008 300C (5.7L) for a stable idle.

    Currently I'm fluctuating about 25 to 50 +/- rpm at idle (in/out of gear). The car has always been like this, I had CMR tunes in the past and am now trying HP tuners. If a 25 rpm range is normal, I understand, and it could just be a pet peeve of mine.

    I've already gotten rid of a low-speed, choppy, partial-throttle, and better WOT response. I'm hoping there's a setting I'm missing or guidance from the forums.

    Mods
    EDIT:
    CAI; JBA shorty headers; cat and reso delete w/ FlowMaster Super 10s



    I am currently waiting for a WB O2 to come in, but wanted to try to get my idle as stable as possible beforehand.
    Anybody have some tips on stabilizing idles to a 5 to 10 +/- target range?

    If you want to see my tune(s)/log(s) just ask.
    Last edited by nmartin6631; 08-04-2020 at 08:37 AM. Reason: forgot CAI

  2. #2
    Senior Tuner SultanHassanMasTuning's Avatar
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    with those mods the rpm should be pretty stable like stock
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  3. #3
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    Try raising the idle a bit

  4. #4
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    I was thinking that too, and there shouldn't be any difference honestly.

    Raised idle up to about 714-720rpm. There was no difference.

    If I kick the A/C in, the idle ups a bit like it's supposed to but then levels back out.

  5. #5
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    This doesn't really sound to far off... But i cant say i really paid much attention to a stock idle quality. I would say since you have removed the cats and added a much more free flowing exhaust along with the cai you more than likely will need a small throttle body adjustment for the add flow through the motor. I would imagine it wouldn't need much change and only in the lower cells for idle.??
    6.4 Whipple Diamond pistons Manley rods, Demon Plus Cam

  6. #6
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    FstdodgeKY,

    That seems to correlate to the logs I've done. RPMs climb steady under throttle, but idle and low speed seem to be a different story. I compared my stock tune to a stock file (2007) and everything matched up 1:1.

    Today I took it out again after the warm up procedure, I was looking at my log and the tune from yesterday looked way off. Not sure if it was the cooler weather today or what, but it felt different than yesterday.

    I took some airflow adjustments out of idle, I even gave it a bump to 810 RPM for idle.

    I wish I could give a log before I got ahold of my mpvi2. It was surging pretty bad around 15 to 20 mph.

    That reminds me, today I finished up the cruise, feeling pretty pleased with the drive, and wondered what would happen at idle in the driveway if I gave it the slightest touch of gas (enough to rest your foot on it and no more). RPMs climbed and fell over and over. To me, the PCM says "3% more throttle, got it. But wait, you barely were out of idle range so I'll back off for you."

    Any help on that last part?

  7. #7
    Quote Originally Posted by nmartin6631 View Post
    I was thinking that too, and there shouldn't be any difference honestly.

    Raised idle up to about 714-720rpm. There was no difference.

    If I kick the A/C in, the idle ups a bit like it's supposed to but then levels back out.
    Sounds like it could be a mechanical problem.. Maybe a vacuum leak.

  8. #8
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    You think so? I thought about that honestly, but it must be very minor, because it's not showing any codes or even sounding like a vacuum leak

  9. #9
    Quote Originally Posted by nmartin6631 View Post
    You think so? I thought about that honestly, but it must be very minor, because it's not showing any codes or even sounding like a vacuum leak
    Yeah they can be pretty subtle and still cause annoying issues.

  10. #10
    if you guys aren't adjusting your friction table for cammed vehicles you're gonna be chasing your tail. Should be one of the first tables you adjust.

  11. #11
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    Nobody said anything about a cam, but thanks for the tip.

  12. #12
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    Quote Originally Posted by luciddeath View Post
    if you guys aren't adjusting your friction table for cammed vehicles you're gonna be chasing your tail. Should be one of the first tables you adjust.
    any advice on adjusting the friction table for a 220/230 comp cam?having sortta the same issue with the stable idle as well.
    By the prickle of my thumb something wicked this way comes!2008 Chrysler 300c! 2013 heads/220/230 comp cam/LTheaders/FTI 2600 stall converter.