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high idle only when moving

This is a discussion on high idle only when moving within the Computer & Tuning forums, part of the LSx Technical Help Section category; Why is it when you are moving the idle is so high it is like having the cruise contol on? ...

  1. #1
    2nd is the first loser ssweet99ss's Avatar
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    high idle only when moving

    Why is it when you are moving the idle is so high it is like having the cruise contol on? I have an 01 ss w/cam and a few bolt ons, m6 when you are driving the idle is very high but when you come to complete stop the idle decreases slowly to about 1000 which is fine but when you take off again it skyrockets. this is very annoying I can unplug the MAF and the idle is low and it does not do the idle up thing, but does run rich. tried different MAF and still doing the same thing. Oh and the car has been tuned but didnt start doing this until approx 6 months later. PLEASE HELP.

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    The Bandit Wesman's Avatar
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    Quote Originally Posted by ssweet99ss View Post
    Why is it when you are moving the idle is so high it is like having the cruise contol on? I have an 01 ss w/cam and a few bolt ons, m6 when you are driving the idle is very high but when you come to complete stop the idle decreases slowly to about 1000 which is fine but when you take off again it skyrockets. this is very annoying I can unplug the MAF and the idle is low and it does not do the idle up thing, but does run rich. tried different MAF and still doing the same thing. Oh and the car has been tuned but didnt start doing this until approx 6 months later. PLEASE HELP.
    My car does the same thing.

    If you are driving down the road at say, 45MPH, and you push the clutch in or put it in neutral, it will idle at like 1400RPM. Then if you keep it in neutral and coast to a stop, the idle gradually drops back down to normal, at 1000RPM.

    I think its a normal feature to keep the revs from dropping too much when you change gears at lower RPM's.

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    Senior Member Too Fast's Avatar
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    My car does the same thing, I think it is normal. Not that I like it, tho. It is worse when the engine is hot.

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    The Bandit Wesman's Avatar
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    It has to be a feature in the PCM, so I'm sure it can be tuned out somehow.

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    Senior Member Too Fast's Avatar
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    Agreed, it probably is able to be tuned out. Just wonder why they did it in the first place.

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    2nd is the first loser ssweet99ss's Avatar
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    My didnt start doing this till here recently and it is starting to get worse, it is almost like having cruise control on, and when you come to a stoplight everybody looks at upu like you are driving a promod car or something, it is starting to get real annoying...............

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    400rwhp::370rwtq Lucky 13's Avatar
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    Mine does the same thing! I hate it! However mine will go back down to normal if i blip the throttle (just tap it down about 1/4 throttle real quick) and it goes up (obviously) and then drops real fast down to normal 1,000. Try that and see what happens

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    2nd is the first loser ssweet99ss's Avatar
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    I will make sure i will try it, how long does it take for it to go back up again, I am willing to try anything right now

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    Moderator Firebirdjones's Avatar
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    It is a feature in the tune. You can eliminate it totally,,,I believe it's called throttle cracker in HPtuners. There is another table as well that will hold throttle up depending on MPH.

    It's on both manual and auto cars.

    You could stick mine in neutral and start rolling or coasting and as MPH picked up,,,,you could watch the rpms climb as high as 1,400 or so.
    I agree, an annoying feature that uses gas if you do alot of coasting,,,and it also doesn't allow as much engine braking when letting off the gas. Thats what I can't stand about it,,,,you end up riding the brakes all the time while going through towns.

    I eliminated it on both of our cars and it's much more pleasurable to drive.

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    Senior Member Too Fast's Avatar
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    "throttle cracker" LOL. Sounds racist!

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    TunedbyFrost.com Tuner Frost's Avatar
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    Quote Originally Posted by Firebirdjones View Post
    It is a feature in the tune. You can eliminate it totally,,,I believe it's called throttle cracker in HPtuners. There is another table as well that will hold throttle up depending on MPH.

    It's on both manual and auto cars.

    You could stick mine in neutral and start rolling or coasting and as MPH picked up,,,,you could watch the rpms climb as high as 1,400 or so.
    I agree, an annoying feature that uses gas if you do alot of coasting,,,and it also doesn't allow as much engine braking when letting off the gas. Thats what I can't stand about it,,,,you end up riding the brakes all the time while going through towns.

    I eliminated it on both of our cars and it's much more pleasurable to drive.


    I agree, BUT...

    If the car did not USE to do this, and has only started recently and has gotten worse; it's not programming, it's something physical.

    A vacuum leak is the first thing that comes to mind.

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    Senior Member clg82's Avatar
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    Quote Originally Posted by Frost View Post
    I agree, BUT...

    If the car did not USE to do this, and has only started recently and has gotten worse; it's not programming, it's something physical.

    A vacuum leak is the first thing that comes to mind.
    Speaking of throttle cracker, do you eliminate this in your mail order tune?

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    TunedbyFrost.com Tuner Frost's Avatar
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    Quote Originally Posted by clg82 View Post
    Speaking of throttle cracker, do you eliminate this in your mail order tune?
    never eliminate, but it definitely won't be OEM...

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    400rwhp::370rwtq Lucky 13's Avatar
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    Quote Originally Posted by ssweet99ss View Post
    I will make sure i will try it, how long does it take for it to go back up again, I am willing to try anything right now
    It never goes back up until you stop and then do it again. So if you decel from 70 and blip the throttle it will drop to normal until you stop, and then if you got back up to 70 you would have to do it again. Make sence?

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    2nd is the first loser ssweet99ss's Avatar
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    Quote Originally Posted by Frost View Post
    I agree, BUT...

    If the car did not USE to do this, and has only started recently and has gotten worse; it's not programming, it's something physical.

    A vacuum leak is the first thing that comes to mind.
    Where could I statr looking for the vacuum leak I have checked everything poss. but i guess I could have missed something.

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    2nd is the first loser ssweet99ss's Avatar
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    Knock on wood.... I think I might have found the prob, I turned the idle down by moving the idle set screw and everything SEEMS to be good i'm gonna drive it some more (weather pemiting) and see how thing go. I will let you guys know how things go as I get to drive the car.

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    What Would Earl Do? Vexzer's Avatar
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    Quote Originally Posted by ssweet99ss View Post
    Knock on wood.... I think I might have found the prob, I turned the idle down by moving the idle set screw and everything SEEMS to be good i'm gonna drive it some more (weather pemiting) and see how thing go. I will let you guys know how things go as I get to drive the car.
    It may return. That throttle screw is just for baseline setting. It's actually the IAC [Idle Air Control Valve] that adjusts you idle airflow volume. The IAC is an electric stepper motor that opens a bypass port in the throttle body to let a measured amount of air past the throttle blade. I run a [FM1-F13-112 [+4] FMS Custom Grind Camshaft - 230"/232" .595"/.585" 112LSA - aggressive profile with a 2500-6800 RPM range, rough idle] cam and had the same high idle problem begin AFTER the car was dyno tuned. Took several trips back to get it right although it's still not perfect. If it was good before, check for trouble codes -not all trip your SES Light, maybe remove and clean the IAC? Maybe a temp sensor or lazy 02? If you cycle the mains on the ECM and it gets better for a while then it's coming from something the ECU is learning during normal use. Go talk to your tuner -they have dealt with this before and ought to give you something to go on.

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    My 99 is doing the same thing. Idle is following cruise speed.
    But only started after I changed from stock to a 92mm FAST TB and Intake.

    Drives fine...brought it from WV to San Antonio...lost gas mileage.

    I tell you I do not like the MAP sensor fit to the intake...I wondered how the Hell it couldn't leak when I put it in. We are warming up here in SA this week and I am going to get some car work done.

    1. I am going to go leak hunting.
    2. Check the MAP signal.
    3. Then I'm going to shim the butterfly on the TB to make sure I'm not choking.
    4. Then check IAC and MAF signals. If it comes down to it I am going to connect a potentiometer to these and then I will try amplifying the signal. (Very small steps of course.)

    -But I think it is something w/ the MAP sensor.

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    Senior Member TransAm11973's Avatar
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    also could be your throttle positioning sensor

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