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  1. #1
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    Drew
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    Default RPM raise for A/C

    I've done some searching and haven't found anything on my issue. My problem is when I run my A/C at idle the car starts to surge to the point that sometimes it will die just sitting still and if I turn the steering wheel it will surely kill it. All I really need to do is to up the idle 200 rpm or so just like any factory car does. Is there some kind of option in LT1 Edit that I am missing that will allow this?

    Info/background - Car is a 96 z28 6spd car that is still on an OBD2 computer. One day I do hope to go OBD1 for easier tuning however that is not going to happen now. Engine mods are head work and custom cam, headers, CAT delete, running on speed density. The PCM was professionally tuned a few years back when the engine work was done. I have LT1 Edit and would like to make some changes and try to get the tune dialed in a little better with some time and practice, however right now I am just trying to fix the dying at idle issue. I live in Oklahoma and it is hot so having an A/C is necessary. When I went in for the tune I didn't have my A/C charged or operational so this issue didn't come up. Thanks for your help!
    1996 Z28, M6, T-tops, stock rear, LE stock ported heads (not typical LE stage, it's a friend of a friend deal), Custom cam and tune from JimTune, CR 11.1, Pacesetter LT, Ram Powergrip HD, flowmaster original 40, Eiback prokit, 18" corvette black wheels from ebay, meizere electric w/p, relocated battery to spare tire well, dd with AC Delco Opti.

  2. #2
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    Default

    @MoeHorsePower

    Sent from my SAMSUNG-SM-G935A using Tapatalk
    1994 Z28 T56 - Le2 H/C, SBE, Hooker lt's, some rod ended suspension stuff, and a whole lotta tetanus
    The wrench for LTConvert's 94 Z28- Ellwein 383/LE2 H/C P600B/ CPT Pro Race/Pro Torque 3200

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  4. #3
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    Default

    Sounds like the IAC valve isn't responding like it's supposed to. It should hold the idle speed constant when any load (A/C, PS) is put on the engine.

    94 Formula A3+1: 381ci forged stroker - Callies Stealth, Oliver 5.85 billet rods, BME nitrous pistons / CNC LT4 heads / Comp Cams solid roller / TH400+GearVendors OD / 4.11's/Strange 12-bolt / 300-shot (dry) N2O / Spohn Suspension / 6-pt roll bar /AutoMeter instrumentation / MoTeC M48 Pro engine management system /a few other odds 'n ends.

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  6. #4
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    Default

    Maybe I am over thinking this and it is just the IAC, but here are some thoughts. I don't have a wild cam so I feel that 900 rpm idle should not be an issue which is why I wasn't concerned about having it working when the car was tuned. What I am seeing is when my A/C is off there is no loading condition that causes trouble at idle. When the A/C compressor kicks on there is a very noticeable engine tone change when it loads up, more so that I had expected and loading the P/S will kill the car. It also seems to have trouble if I push the brake pedal more than once within about 2 seconds only if the A/C is on. When I did the engine rebuild the IAC motor was something that I cleaned up but did not replace.

    I can't seem to attach an image of my cam card so the specs are
    Lift - .535 .534
    Duration @ .050 - 218 230
    Lobe sep - 111
    1996 Z28, M6, T-tops, stock rear, LE stock ported heads (not typical LE stage, it's a friend of a friend deal), Custom cam and tune from JimTune, CR 11.1, Pacesetter LT, Ram Powergrip HD, flowmaster original 40, Eiback prokit, 18" corvette black wheels from ebay, meizere electric w/p, relocated battery to spare tire well, dd with AC Delco Opti.

  7. #5
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    Quote Originally Posted by okst8engineer View Post
    Maybe I am over thinking this and it is just the IAC, but here are some thoughts. I don't have a wild cam so I feel that 900 rpm idle should not be an issue which is why I wasn't concerned about having it working when the car was tuned. What I am seeing is when my A/C is off there is no loading condition that causes trouble at idle. When the A/C compressor kicks on there is a very noticeable engine tone change when it loads up, more so that I had expected and loading the P/S will kill the car. It also seems to have trouble if I push the brake pedal more than once within about 2 seconds only if the A/C is on. When I did the engine rebuild the IAC motor was something that I cleaned up but did not replace.

    I can't seem to attach an image of my cam card so the specs are
    Lift - .535 .534
    Duration @ .050 - 218 230
    Lobe sep - 111
    could have messed the iac up, or whoever tuned it didn't raise any of the ac/ps iac follower tables.

    Sent from my SAMSUNG-SM-G935A using Tapatalk
    1994 Z28 T56 - Le2 H/C, SBE, Hooker lt's, some rod ended suspension stuff, and a whole lotta tetanus
    The wrench for LTConvert's 94 Z28- Ellwein 383/LE2 H/C P600B/ CPT Pro Race/Pro Torque 3200

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  9. #6
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    Default

    You mention AC/PS IAC follower tables. Which tables would that be? I am just now trying to learn to tune and assumed there had to be something that dealt with A/C. Is there a good basic tutorial out there that would explain to me which tables I would need to modify? Sorry if these are ignorant questions this is very new to me.

    I have not found much about OBD2 tuning and I haven't ready the OBD1 tuning guides because I assume they are too different to do me any good. Would the OBD1 tuning guides help?

    Thanks!
    1996 Z28, M6, T-tops, stock rear, LE stock ported heads (not typical LE stage, it's a friend of a friend deal), Custom cam and tune from JimTune, CR 11.1, Pacesetter LT, Ram Powergrip HD, flowmaster original 40, Eiback prokit, 18" corvette black wheels from ebay, meizere electric w/p, relocated battery to spare tire well, dd with AC Delco Opti.

  10. #7
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    Quote Originally Posted by okst8engineer View Post
    You mention AC/PS IAC follower tables. Which tables would that be? I am just now trying to learn to tune and assumed there had to be something that dealt with A/C. Is there a good basic tutorial out there that would explain to me which tables I would need to modify? Sorry if these are ignorant questions this is very new to me.

    I have not found much about OBD2 tuning and I haven't ready the OBD1 tuning guides because I assume they are too different to do me any good. Would the OBD1 tuning guides help?

    Thanks!
    the obd2 lt1 software is pretty much the same as obd1 software, as cats tuner developed it and sold the rights to jet which is now the jet dst software. what software are you using?

    download an obd1 timing program and look at the tables, they are clearly marked. if you're that green about it talk to moe Bailey about having him do it for you. by the time you buy the obd2 software, a spare pcm(obd2 pcms love to brick) you could've paid to have him do it

    Sent from my SAMSUNG-SM-G935A using Tapatalk
    1994 Z28 T56 - Le2 H/C, SBE, Hooker lt's, some rod ended suspension stuff, and a whole lotta tetanus
    The wrench for LTConvert's 94 Z28- Ellwein 383/LE2 H/C P600B/ CPT Pro Race/Pro Torque 3200

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  12. #8
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    Default

    I have to start somewhere to learn what I'm doing and I figured since the rest of the tune is there and working I could give this a shot. I have LT1 Edit software I bought it about 10 years ago to make minor changes and from what I remember it was all I could find back then. I will always be tinkering with this car and would like to be able to tune it myself. I know OBD2 PCMs like to brick and do plan to convert one day but in the short term I already have the software and would like to get the car more friendly to daily drive. I was an ASE certified technician for about 6 years and an aircraft mechanic in the AF for 4 and am now an engineer so I have the ability to learn and figure it out myself. I will start with researching and figures asking questions on here was as good a start as any.
    Thanks for the input!
    1996 Z28, M6, T-tops, stock rear, LE stock ported heads (not typical LE stage, it's a friend of a friend deal), Custom cam and tune from JimTune, CR 11.1, Pacesetter LT, Ram Powergrip HD, flowmaster original 40, Eiback prokit, 18" corvette black wheels from ebay, meizere electric w/p, relocated battery to spare tire well, dd with AC Delco Opti.

  13. #9
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    Quote Originally Posted by okst8engineer View Post
    I have to start somewhere to learn what I'm doing and I figured since the rest of the tune is there and working I could give this a shot. I have LT1 Edit software I bought it about 10 years ago to make minor changes and from what I remember it was all I could find back then. I will always be tinkering with this car and would like to be able to tune it myself. I know OBD2 PCMs like to brick and do plan to convert one day but in the short term I already have the software and would like to get the car more friendly to daily drive. I was an ASE certified technician for about 6 years and an aircraft mechanic in the AF for 4 and am now an engineer so I have the ability to learn and figure it out myself. I will start with researching and figures asking questions on here was as good a start as any.
    Thanks for the input!
    I'm not sure of the tables in lt1 edit, I've never used it. I know in cats there is throttle follower vs a.c. vs iac tables, as well as a.c. anticipate tables, etc.

    Sent from my SAMSUNG-SM-G935A using Tapatalk
    1994 Z28 T56 - Le2 H/C, SBE, Hooker lt's, some rod ended suspension stuff, and a whole lotta tetanus
    The wrench for LTConvert's 94 Z28- Ellwein 383/LE2 H/C P600B/ CPT Pro Race/Pro Torque 3200

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  15. #10

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    There are idle table tables for both park and neutral, IAC and follower tables in LT1 edit, also what are your IAC counts?

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