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Tuner won't tune car cause of Po103 ?

This is a discussion on Tuner won't tune car cause of Po103 ? within the Forced Induction forums, part of the LSx Technical Help Section category; ...

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    Tuner won't tune car cause of Po103 ?

    I took my car to get tuned today, which is a stock 98' Procharged LS1 Camaro at 7-8#.

    Previously, he tried to tune it but stated that I had a vacumn leak. This was causing the idle to fluctuate or roll and showed a lean A/F mixture and also the long term fuel trim was maxed out. He pointed out that we had an LS6 intake with the LS1 coolant pipes still installed. So we took them off and installed the LS6 coolant lines and new intake seals for fear that this was causing a vacumn leak. We still had an issue with the idle fluctuating even after we checked everywhere for vacumn leaks. I will note though, that the idle did improve a little. Still, he would not put the car on the dyno because he said the computer was not able to go into a closed loop and let the sensors control the engine. To compensate for this, he set the fuel mixture on the rich side. The vacumn reading was 17-20,which increased to 20-22 after the intake was removed.

    We brought it back to the tuner even though we still had an SES light, but we figure that it was still popping up due to the lack of a complete tune while only under full throttle. The trouble code is a PO103, which is the MAF reading a higher than expected voltage or airflow. At the same time my A/F was reading 16:1. Now I have read that this can cause the A/F to lean out. I cleaned it with MAF cleaner and still no better, so we got the idea to disconnect the MAF and suddenly the car idled perfect and the A/F dropped to 14.7:1 !!! What is the problem? Is my MAF bad or could I still have a vacumn leak? I do have a de-screened MAF, could this cause it?

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    Gold Member BlwnCamaro's Avatar
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    Quote Originally Posted by 9t8z28 View Post
    I took my car to get tuned today, which is a stock 98' Procharged LS1 Camaro at 7-8#.

    Previously, he tried to tune it but stated that I had a vacumn leak. This was causing the idle to fluctuate or roll and showed a lean A/F mixture and also the long term fuel trim was maxed out. He pointed out that we had an LS6 intake with the LS1 coolant pipes still installed. So we took them off and installed the LS6 coolant lines and new intake seals for fear that this was causing a vacumn leak. We still had an issue with the idle fluctuating even after we checked everywhere for vacumn leaks. I will note though, that the idle did improve a little. Still, he would not put the car on the dyno because he said the computer was not able to go into a closed loop and let the sensors control the engine. To compensate for this, he set the fuel mixture on the rich side. The vacumn reading was 17-20”,which increased to 20-22” after the intake was removed.

    We brought it back to the tuner even though we still had an SES light, but we figure that it was still popping up due to the lack of a complete tune while only under full throttle. The trouble code is a PO103, which is the MAF reading a higher than expected voltage or airflow. At the same time my A/F was reading 16:1. Now I have read that this can cause the A/F to lean out. I cleaned it with MAF cleaner and still no better, so we got the idea to disconnect the MAF and suddenly the car idled perfect and the A/F dropped to 14.7:1 !!! What is the problem? Is my MAF bad or could I still have a vacumn leak? I do have a de-screened MAF, could this cause it?
    hard to say over internet description, but descreening maf will definately not cause this. As for a vacum leak the old school trick of spraying carb cleaner at idle at no boost spray around suspected area if the engine idles down or tries to die it is sucking in air there. Your maf could be bad i'd try different maf from friend before you buy one or see if you can have maf checked before you toast engine 16:1 a/f + boost = toasted engine. Are your injectors and fuel pump stock also? The computer is basically telling you the maf is out of acceptable range with that code. Just by description without checking car in person though and diagnosing its hard to say, but would definately check maf. Those new variable programmable hi flo mafs are baddass. When you unplugged maf computer went into a sort of default mode.
    Last edited by BlwnCamaro; 06-05-2008 at 09:42 PM.

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    Quote Originally Posted by BlwnCamaro View Post
    hard to say over internet description, but descreening maf will definately not cause this. As for a vacum leak the old school trick of spraying carb cleaner at idle at no boost spray around suspected area if the engine idles down or tries to die it is sucking in air there. Your maf could be bad i'd try different maf from friend before you buy one or see if you can have maf checked before you toast engine 16:1 a/f + boost = toasted engine. Are your injectors and fuel pump stock also? The computer is basically telling you the maf is out of acceptable range with that code. Just by description without checking car in person though and diagnosing its hard to say, but would definately check maf. Those new variable programmable hi flo mafs are baddass. When you unplugged maf computer went into a sort of default mode.
    The A/F is around 14.7:1 whenever there is a load on the engine. At WOT, the A/F goes to 10.5:1 and it is only at 16:1 when idling. The tuner has it set up this way to be safe until I figure out the problem

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    Gold Member BlwnCamaro's Avatar
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    Quote Originally Posted by 9t8z28 View Post
    The A/F is around 14.7:1 whenever there is a load on the engine. At WOT, the A/F goes to 10.5:1 and it is only at 16:1 when idling. The tuner has it set up this way to be safe until I figure out the problem
    Oh okay thats very rich under wot better safe than sorry right! Good luck man wish I could help you more, im not computer tuning expert but pretty good at mechanical aspect.

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    Has anyone messed with the MAF calibration table or the MAF sensor fail high frequency threshold in the VCM file? If not, then your MAF sensor might be close to the permanent failure grave.

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    Quote Originally Posted by GatorSS View Post
    Has anyone messed with the MAF calibration table or the MAF sensor fail high frequency threshold in the VCM file? If not, then your MAF sensor might be close to the permanent failure grave.
    Can you explain this to me?

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    Junior Member Chad Nielson's Avatar
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    I would try the maf first, your local auto parts store might let you try a new one. If it works your golden. If not, the tuner, (if he is good) can tune for that problem, by setting the maf table to the correct setting for idle. Also ask him what program he is using to do the tuning. He should be able to switch it to speed density then you will not have to worry about the maf.

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    Quote Originally Posted by Chad Nielson View Post
    I would try the maf first, your local auto parts store might let you try a new one. If it works your golden. If not, the tuner, (if he is good) can tune for that problem, by setting the maf table to the correct setting for idle. Also ask him what program he is using to do the tuning. He should be able to switch it to speed density then you will not have to worry about the maf.
    I just installed the new MAF and it runs alot better but not perfect.

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