Thread: P0171 and P0300 Codes, Mildly Rough Idle, Rough on starts, Slightly Elevated Idle

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  1. #1 Re: P0171 and P0300 Codes, Mildly Rough Idle, Rough on starts, Slightly Elevated Idle 
    Turbo is the way to go. BillBoost37's Avatar
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    To throw 171 aka lean bank 1 you need to have been out of the acceptable range 3 consecutive time running. This means you are over 16.4% fuelling being added by the pcm. So it's telling you.

    Flashing CEL means that the PCM sees a potential catalyst damaging condition aka you had misfires based on the code.

    From what you are saying.. it sounds like you have a vacuum leak. You did the right thing, you checked for a vacuum leak. Except, there's one smaller leak that you can never find with starter fluid. Remove the pipe from the EGR to LIM and pull back the retaining piece, then look where the retainer would hold the lip for cracks. Likely...it's cracked, 90% of them are cracked.

    Now that's not giving you enough to go on for a true fix. Let's jump in deeper and talk about fuelling. 41 at idle is fine in my experience for the average SC motor. Does the pressure increase properly when you remove the vacuum from the FPR? What does the fueling do when you are driving? (I made an extension pressure hose).

    Keep in mind that the swivelling plastic piece in the hose at the brake booster is also a check valve. Shouldn't be an issue, I have seen one or two cause a problem though.
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  2. #2 Re: P0171 and P0300 Codes, Mildly Rough Idle, Rough on starts, Slightly Elevated Idle 
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    Quote Originally Posted by BillBoost37 View Post
    To throw 171 aka lean bank 1 you need to have been out of the acceptable range 3 consecutive time running. This means you are over 16.4% fuelling being added by the pcm. So it's telling you.

    Flashing CEL means that the PCM sees a potential catalyst damaging condition aka you had misfires based on the code.

    From what you are saying.. it sounds like you have a vacuum leak. You did the right thing, you checked for a vacuum leak. Except, there's one smaller leak that you can never find with starter fluid. Remove the pipe from the EGR to LIM and pull back the retaining piece, then look where the retainer would hold the lip for cracks. Likely...it's cracked, 90% of them are cracked.

    Now that's not giving you enough to go on for a true fix. Let's jump in deeper and talk about fuelling. 41 at idle is fine in my experience for the average SC motor. Does the pressure increase properly when you remove the vacuum from the FPR? What does the fueling do when you are driving? (I made an extension pressure hose).

    Keep in mind that the swivelling plastic piece in the hose at the brake booster is also a check valve. Shouldn't be an issue, I have seen one or two cause a problem though.
    Good information thank you. so is the car over fueling itself right now or running too lean? I'm just worried about burning a valve from lean, but I'm also not a fan of driving my Z06 everyday either... lol First world issues I guess? I'll check that EGR piece out. def could be the issue, all the symptoms point to a vac leak for sure. its just so odd tho when i gave it a lot of throttle though how it really fell on its face. its like it drown almost.

    I'll have to check the fuel stuff later on tonight when I get home. going to be a late night again. but any night in the shop is still fun i guess.

    What do you mean "Now that's not giving you enough to go on for a true fix." you think there is more than a vac leak? I guess youre right, a tiny vac leak shouldnt cause all this?

    When I pull the vac line off the FPR what shoudl the pressure rise too? I will do this as well.
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