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Help with a po507

This is a discussion on Help with a po507 within the LT1 forums, part of the Vehicle Specific category; The car is a 97 z28 98k 6spd stock besides borla ,bbk tb ,and k&n with a paper cone I've ...

  1. #1
    Member Ieatstangs's Avatar
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    Help with a po507

    The car is a 97 z28 98k 6spd stock besides borla ,bbk tb ,and k&n with a paper cone I've cleaned the maf numerous times
    I've replaced the iac and the tps
    I've searched everywhere for vacuum leaks haven't found any it idles at a little over 1000
    It also sticks at about 2k when I put it in neutral it'll eventually drop down when I come to a complete stop any help and advice would be greatly appreciated

    The maf has been descreened can't find a used one anywhere I'd hate to buy a new one and I butchered the one i took off my 98 could this cause it?

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    Senior Member 5.0THIS's Avatar
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    Descreening a MAF doesnt typically cause a po507. It's most likely the throttle body. Put the stocker back on. The BBK isnt doing anything for the car anyway at it's current mod level. You can also double check your current IAC and TPS to make sure they are ok. Did you use some carb cleaner (or similar) to check for vacuum problems around the intake manifold? That might be another thing to check.

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    Senior Member bigrondownhiller's Avatar
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    Also check the stock rubber elbow. Mine developed a small crack in the bottom right where it goes on the tb.

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    Member Ieatstangs's Avatar
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    i bought the car with the tb so i dont have a stocker....yes i have sprayed around the intake for vaccum leaks i didnt find anything ill check the elbow and the iac and tps with a voltmeter today thanks

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    Senior Member 5.0THIS's Avatar
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    I'd change out the throttle body to a stocker. I imagine you can find one fairly cheap.

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    Member 383ls6's Avatar
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    1. Using a scan tool, try commanding the Idle Air Control (IAC) down, the idle should come down with the command.

    2. If the idle remains high when commanded lower, check for vacuum leaks.

    3. If no vacuum leaks, check the signal from the Powertrain Control Module (PCM) to the IAC using a lab scope or a logic probe. When commanded up or down, there should be a digital 12 volt signal on each of the 4 wires. If no signal was found on any one or more of the wires, check the wire from the IAC connector back to the PCM and the connector at the PCM.

    4. If the signal is OK on all four wires, plug the IAC hole off (located on the inside of the throttle bore) and see if the idle will come down. If the ideal comes down with the IAC hole blocked off, and there is a signal on all four wires, the IAC will need to be replaced.
    Potential Causes: Leaking Engine Vacuum
    Idle Air Control (IAC)
    Powertrain Control Module (PCM)
    Wiring

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    Member Ieatstangs's Avatar
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    Quote Originally Posted by 5.0THIS View Post
    I'd change out the throttle body to a stocker. I imagine you can find one fairly cheap.
    Yeah im hoping too

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    Member Ieatstangs's Avatar
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    99z28 a4

    Quote Originally Posted by 383ls6 View Post
    1. Using a scan tool, try commanding the Idle Air Control (IAC) down, the idle should come down with the command.

    2. If the idle remains high when commanded lower, check for vacuum leaks.

    3. If no vacuum leaks, check the signal from the Powertrain Control Module (PCM) to the IAC using a lab scope or a logic probe. When commanded up or down, there should be a digital 12 volt signal on each of the 4 wires. If no signal was found on any one or more of the wires, check the wire from the IAC connector back to the PCM and the connector at the PCM.

    4. If the signal is OK on all four wires, plug the IAC hole off (located on the inside of the throttle bore) and see if the idle will come down. If the ideal comes down with the IAC hole blocked off, and there is a signal on all four wires, the IAC will need to be replaced.
    Potential Causes: Leaking Engine Vacuum
    Idle Air Control (IAC)
    Powertrain Control Module (PCM)
    Wiring
    thank you very much ill give it a try today

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    Member Ieatstangs's Avatar
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    okay so i plugged the hole on my tb and it ran better whenever i put it in neutral the rpms would drop and i notice it backfires now but that is the least of my concerns it ran 7 monitors before it threw a code now its p1507 which means the iac isnt functioning properly. the iac is new but it may be bad or is this a pcm problem ill be getting a stock tb as soon as i can find one less than $100 the tow yards and junkyards here are rip off artists

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