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idle is fine with A/C on but jumpy when its off?

This is a discussion on idle is fine with A/C on but jumpy when its off? within the General Help forums, part of the LSx Technical Help Section category; Hi guys. i recently did the LS6 valley cover upgrade. Its been fine but I did noticed that when the ...

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    Senior Member JayTA98's Avatar
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    idle is fine with A/C on but jumpy when its off?

    Hi guys. i recently did the LS6 valley cover upgrade. Its been fine but I did noticed that when the car's a/c is off the idles tends to get jumpy. the car kinda jerks lightly but it doesn't shut off. Im just wondering why will the idle be almost perfect with the a/c on. The RPM stays steady at 800 with the a/c on and about 700 with a/c off.

    Prior to the valley cover upgrade i had idle issues. I found out that the valley cover gasket was bad when i replaced the valley cover.
    I have a question about the 3 way valve that sits by the PCM area. I know one vacuum line comes from the back of the intake to it. Then it splits in two: one to the inside of the car and one goes to the front of the vehicle thru the passenger side of the engine bay. Where does this line going towards the front connects to? I even capped that line and there is no changes in the idle but i wonder where does it goes to. Thanks.

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    O U 8 1 2 Spaz's Avatar
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    my car usually raisees the rpm by 100 or so when i turn the AC on... seems normal...

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    Senior Member JayTA98's Avatar
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    Quote Originally Posted by Spaz View Post
    my car usually raisees the rpm by 100 or so when i turn the AC on... seems normal...
    tha part is fine. but the idle stays jumpy all the time with the a/c off.

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    O U 8 1 2 Spaz's Avatar
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    Quote Originally Posted by JayTA98 View Post
    tha part is fine. but the idle stays jumpy all the time with the a/c off.
    when you start your car is the AC on or off??? reason i ask is my car will run a bit different depends on that... maybe it's my tune???
    Last edited by Spaz; 07-08-2011 at 07:44 AM.

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    Smiles for 9.5 Years cammed goat's Avatar
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    Could be the A/C putting a parasitic drag on the engine while the compressor is on, causing the idle to drop so the erradic idle isn't really noticed. Without the A/C running, is the idle lopey?

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    Senior Member JayTA98's Avatar
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    Quote Originally Posted by cammed goat View Post
    Could be the A/C putting a parasitic drag on the engine while the compressor is on, causing the idle to drop so the erradic idle isn't really noticed. Without the A/C running, is the idle lopey?
    with the a/c the idle is almost perfect I don't notice anything wrong. with the a/c off the idle feels like it spikes. it almost feels when a spark plug is bad or arcing. I changed the wired like 6 months ago. The plugs were changed around 10k ago with ngk
    tr55's. Today the car spiked hard for like a second. most of the time it stays kinda spiky but is not a steady pattern. it could be fine for like 5 second and then spikes. I guess because i have poly mounts i feel it more.

    I might go ahead and replace the plugs this weekend and check the wires as well. I had this problem since I own the car. It used to happen all the time even with the a/c on. Since i changed the valley cover it doesn't do it with the a/c on anymore or at least i don't notice it. No SES light.

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    Smiles for 9.5 Years cammed goat's Avatar
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    It could be the current draw from the fans. Are the plugs TR55's or TR55 IX?

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    Senior Member JayTA98's Avatar
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    Quote Originally Posted by cammed goat View Post
    It could be the current draw from the fans. Are the plugs TR55's or TR55 IX?
    tr55's. well i doubt is the fans because it occurs even from a cold engine start. I can hear when my fan turn on and it doesn't make a difference. i have a new set ac delco iridiums in the garage.

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    Smiles for 9.5 Years cammed goat's Avatar
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    Quote Originally Posted by JayTA98 View Post
    tr55's. well i doubt is the fans because it occurs even from a cold engine start. I can hear when my fan turn on and it doesn't make a difference. i have a new set ac delco iridiums in the garage.
    OK. Install the Delcos and get back to us.

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    Veteran 0rion's Avatar
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    what mods do you have and is the car tuned? Idle airflow will change when you turn the a/c on so that might be helping your idle issue. You say you had this issue before the valley cover? Same exact issue?

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    Senior Member JayTA98's Avatar
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    well i noticed this morning that when I was leaving work(cold engine) I put it in drive and the rpms drop to 500. I put it in neutral and it got alittle better but I can tell something was going on. I put in reverse and same thing. I kinda of heard some clunking noise in the engine area when I tried to move but it stopped. i put it in neutral again and the rpms went back up to 800. I park and waited for a bit and everything was normal again. Drove all the way home with no issues.

    Not sure if it is related with my initial post here. The car never died. im going to replace the plugs today. Im thinking maybe i shoud replace my IACV but it cost around $110.

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    Senior Member JayTA98's Avatar
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    Quote Originally Posted by 0rion View Post
    what mods do you have and is the car tuned? Idle airflow will change when you turn the a/c on so that might be helping your idle issue. You say you had this issue before the valley cover? Same exact issue?
    yes i had this issue before but it got better with the valley cover. Today I changed the spark plugs. They looked okay but I will post pics of them. I checked my plug wires and 4 of them showed open, now thats kinda of rare as i will think the car will missfire. Im not sure if the cables are snaping when i pull them out. I start the car and the idle is alot better.

    Everytime I change the plugs and replace wires it seems to get better and then with time it goes back to the same issue. Im not sure if the cables are degrading. I will keep an eye on the idle and post updates.
    1998 TA 130k A4, LS6 intake, TunedByFrost, Airlid, AIR and EGR delete, Borla exhaust, front Eibach lowering springs, LS6 valley cover, UMI TQ arm, UMI LCA's, UMI panhard bar, Poly engine mounts, BMR relocation brackets, Blistein HD shocks and struts, Oil catch can, Autotrix window fix.

    Now I have an 2001 F150 5.4L

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    Smiles for 9.5 Years cammed goat's Avatar
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    Do you clean your engine and engine compartment? If you do, what do you use to clean it with?

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    Senior Member JayTA98's Avatar
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    Quote Originally Posted by cammed goat View Post
    Do you clean your engine and engine compartment? If you do, what do you use to clean it with?
    When I clean it I use diluted degreaser and a water hose at shower setting. I don't soak the engine. I then use an air blower to get rid of the residual water.

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    Smiles for 9.5 Years cammed goat's Avatar
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    OK. I only ask as I was wondering if the stuff you used possibly ate through your plug wires.

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    Quote Originally Posted by JayTA98 View Post
    When I clean it I use diluted degreaser and a water hose at shower setting. I don't soak the engine. I then use an air blower to get rid of the residual water.
    I'm nominating you second in line this week for the "my knock sensors are bad" thread These motors hate water.....nothing but bad can come of putting water on them.


    How close are your plug wires to your headers? If they're close enough the headers will dry out and crack plug wires.....and it doesn't take as long as you might think. My buddy has a 98 vette and his #7 wire is right on that primary. Even with kevlar sleeves he has to replace that wire every couple years depending on how much he drives the car.

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    Senior Member JayTA98's Avatar
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    Quote Originally Posted by 0rion View Post
    I'm nominating you second in line this week for the "my knock sensors are bad" thread These motors hate water.....nothing but bad can come of putting water on them.


    How close are your plug wires to your headers? If they're close enough the headers will dry out and crack plug wires.....and it doesn't take as long as you might think. My buddy has a 98 vette and his #7 wire is right on that primary. Even with kevlar sleeves he has to replace that wire every couple years depending on how much he drives the car.
    I just replaced the sensors lol. Only because I did the valley cover. I don't have headers.

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    Smiles for 9.5 Years cammed goat's Avatar
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    You didn't overtighten those sensors...did ya? Just asking as if you under/overtighten them, they will create a "false knock".

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    Senior Member JayTA98's Avatar
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    Quote Originally Posted by cammed goat View Post
    You didn't overtighten those sensors...did ya? Just asking as if you under/overtighten them, they will create a "false knock".
    No, I follow the write up and torque to specs.

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    did you upgrade to the 99+ sensors and harness or just replace the 98's? The 98 sensors are fairly retarded really....way more sensitive than the 99+.

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