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Thread: LE5 Idle Tuning for Emissions

  1. #1
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    LE5 Idle Tuning for Emissions

    Need some help from the experts. I have an LE5 E67 Gen 4 from an '07 Sky swapped into my VW bus. Conversion is complete and has working VVS, EVAP, etc. but no Clutch Position Sensor. Has CAI and 2.25 exhaust - otherwise stock. Runs great after some minor tuning VE and MAF tuning.

    Here's where I need some help. I'm trying to get it through all readiness monitors to pass CA smog. It passes everything except the CAT test - it never runs (confirmed with Tech 2 scanner). Did some research and understand that the CAT monitor sets when P0420 cat efficiency test completes. One of the parameters for P0420 to run is Idle condition with TP of less than 2% (among other factors that appear fine). Mine fluctuates between 2-2.3% and I can't figure out how to bring it down below 2%. The idle is decent, but fluctuates with an O2 drop every 15 seconds or so that I don't know the cause of. Seems like that may be pushing the throttle to open to bring the idle back up. I've read up on all sorts of idle threads and played around with the Idle base timing, Base Airflow Final Minimum and ECT Mult settings but nothing seems to help and most only make the idle worse.

    Anyone have any ideas on what I should be trying to get the throttle closed just a little bit further at idle? Thanks!

    Current Bus Tune - 05-04-19 - tune from old OS - idle air 90%.hpt
    Log 3.hpl

  2. #2
    Senior Tuner cobaltssoverbooster's Avatar
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    if you want the throttle to close more i would start by commanding more ignition at idle and making the ignition stable while your in there.
    2000 Ford Mustang - Top Sportsman

  3. #3
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    Thanks for the reply. I tried adding timing earlier but was a little too aggressive in my adjustments and it made the problem worse. This time I added only 2 degrees to the lower part of the idle advance table. I also dialed down the target idle values by 50 rpm. So far the impact looks positive but we'll see if it runs the test.

    I didn't quite understand what you mean by making the ignition stable. As in the same values? Or something else? Thanks again.

  4. #4
    Senior Tuner cobaltssoverbooster's Avatar
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    Your main spark table is your idle ignition table so long as the idle spark adder is set to 0. Now make a histogram that is identical to your main spark table and record the cells in which it idles through. Make all those cells the same value in the main spark map. Over speed and under speed will control any surges for you. Just give it a stable region to work from.