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Thread: 94 IAC

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    Member 94conv.'s Avatar
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    Default 94 IAC

    Ok Ive posted here about this not to long ago, but the problem or lack of diagnosis is still present. First off, after a long 5 hour drive I came home, the car sat for about two hours, and then I started it to take it out again, it idled real low, 500 and slightly below, stumbled. Shut it off, cleaned the IAC thinking it was carboned up. Hooked it back up and started it. Idled to 1500 then down to 800 where it belongs, thats what it keeps doing now, I just checked for any vacuum leaks and didnt find any. Sprayed throttle body cleaner, highly flammable around the connections, no change whatsoever. I'm thinking its the IAC motor going bad. Once it idles down it runs great, its only when you start it that it revs to 1500 and then down to normal, within a few seconds, maybe 10. Any advice or anything else Im missing before I order this 90 some dollar part? I am going to Gm to get the part this time, I think I replaced that IAC about 3 years ago and got it from advanced auto and it cost like 40 bucks, gm's is more the twice that with a different number that doesnt cross reference the number that I just got a week ago from O'rielys which is also about 40 or 50 bucks. I also unhooked the IAC and started it and it went to 1500 and stayed there, didnt attempt to come down. so I plugged it back in and once again it went to 1500 then back down to 800.

    Thanks.

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    If you have a scan tool post the IAC counts when the problem occurs.

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    Member 94conv.'s Avatar
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    Sorry, I dont have a scan tool. Thanks for the reply

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    Quote Originally Posted by 94conv. View Post
    Ok Ive posted here about this not to long ago, but the problem or lack of diagnosis is still present.
    Quote Originally Posted by 94conv. View Post
    Sorry, I dont have a scan tool. Thanks for the reply
    Thats why we Professionals get the Big Bucks!!
    We have the Manuals!
    We have the Proper Test Equipment!!
    We have the Know How!!

    I don't know what your problem is without proper Trouble shooting,
    But I'd almost be willing to bet it's NOT the IAC, seams to me It's doing what it's supposed to be doing!!
    It's got so it seems to me that the Internet has created a lot more Horses A$$'s than we have Horses!
    junk!~!!
    Founding Member: 10 Corvettes Anonymous


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    Member 94conv.'s Avatar
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    I'm trying to avoid some big bucks here if I can. Do you think leaking injectors or an oxygen sensor could also cause this? Do all injectors for all years ohm at 16-17 ohms when theyre good or are different years different ohms? I may try to ohm them out later on today. Someone else mentioned TPS but it runs fine once it idles down. It doesnt want to run away from you with the brakes on at a stop light and idles fine when in gear while stopped.

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    Member gmjunkie's Avatar
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    Quote Originally Posted by 94conv. View Post
    I'm trying to avoid some big bucks here if I can. Do you think leaking injectors or an oxygen sensor could also cause this? Do all injectors for all years ohm at 16-17 ohms when theyre good or are different years different ohms? I may try to ohm them out later on today. Someone else mentioned TPS but it runs fine once it idles down. It doesnt want to run away from you with the brakes on at a stop light and idles fine when in gear while stopped.
    16.5 is optimal,Gm says to replace below 10 ohms,they will very a little sometimes I like'm at least above 13.5 or better but I don't think it's your injectors either! TPS is possible,Temp Sensor is possible too,The biggest things I've found are Temp Sensors out of range,TPS out of range,Bad Connections and GROUNDS on these cars!! I had a problem a while back on my 94 LT1 6 sp, Pulled my hair out for a couple weeks,It ended up being the Ground's on the main harness at the back of the block!! Clean All the Engine and Chassis Grounds good and then go from there!! There are so many things that can cause this,thats why it's about impossible to diagnose without a good scanner that you can read in a Data Mode!!

    It's got so it seems to me that the Internet has created a lot more Horses A$$'s than we have Horses!
    junk!~!!
    Founding Member: 10 Corvettes Anonymous


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    Member 94conv.'s Avatar
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    Thanks Junkie.

  8. #8
    MBDiagMan
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    junkie is definitely onto something here. It will often cost you MUCH less, to have the problem diagnosed, than it will to start throwing parts at the problem. That's the government way, you know, you got a problem so you just throw a bunch of money at it and then wonder why the problem gets worse.

    If you don't have the equipment, data and knowledge to properly troubleshoot the problem, you will probably be surprised to find how little it will cost to have it done by someone that has all these things.

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    Member 94conv.'s Avatar
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    I may try and get it in on Monday. Surely they'd have it done by the weekend. Thanks again.

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    Quote Originally Posted by gmjunkie View Post
    Thats why we Professionals get the Big Bucks!!
    We have the Manuals!
    We have the Proper Test Equipment!!
    We have the Know How!!

    I don't know what your problem is without proper Trouble shooting,
    But I'd almost be willing to bet it's NOT the IAC, seams to me It's doing what it's supposed to be doing!!

    Right on Junk! I'm reminded of a post on another forum where the owner figured he would save some money by changing his own valve cover gaskets. Seems like an easy project a backyard guy could handle right? WRONG!!!
    Turned into a horror story after he broke off some cover bolts, then drilled into a water jacket trying to remove the broken bolts! Eventually required removal of the head for machine shop repair. Don't think he saved much on that job.

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    Member 94conv.'s Avatar
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    Ok, so the only time this thing idles high is on start up so I went ahead and paid the money and go the gm IAC. Its a heavier part then the one from the auto parts store or seems to be, and I replaced it, it idled high twice then I drove it for about 5 miles and now its back to normal.

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