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Thread: Running RICH, Engine NOT following commanded values.

  1. #1

    Default Running RICH, Engine NOT following commanded values.

    I have a N/A Gen3 Hemi. Methanol fuel, NTK WBO2 sensors. We moved the engine/Holley Dominator and harnesses from one car to another. It was running great in the other car. WBO2s are located in open headers, in the same location as in the previous car.
    On startup AFR goes richer than the commanded values in less than two seconds. In the attached datalog at 166 second mark it starts to run closer to commanded AFR.

    So far we have:
    Searched on this forum for ideas.
    Confirmed PCM + and - to the battery.
    Cleared Learn Table.
    Cleaned and scaled injectors.
    New fuel.
    Hotter plugs for this tuning phase only.
    Replaced sensors.
    MAP, Cam, Position, Crank Position, etc.
    Disconnected Holley PCM from battery for an hour.
    Checked each cylinder for spark and timing.
    Leak down test.
    Cleared Enabled Closed Loop table.

    I've ordered a new NTK WBO2 sensor to eliminate another variable. I believe AFR would go LEAN if WBO2s had failed. Thanks for your help.
    Click image for larger version. 

Name:	AFR_decay_after_start_up.jpg 
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    Last edited by HRH; 01-28-2020 at 03:16 PM.

  2. #2


    What does it do in Open Loop? Andrew
    IG @projectgattago

  3. #3


    Hard to see much in your picture, but it looks like you have coolant enrichment on. Is the Target AFR 8.0 and the actual AFR is 5.4? I can't really see the numbers. Did you open the datalog and use the Overlay function to look at all of the tables in your tune? Typically the system does what it's being told to do, so you need to look at all of the tables to see if fuel is being added somewhere.

    If the system is doing something that isn't programmed, then that usually means that a sensor has failed or something else is corrupting the process. In your case, if the Target is 8.0 and the actual is 5.4, then it would appear that the system knows the actual AFR is rich. I can't tell if Learn is on or not, but the picture shows that Current Learn is -25%. So it appears to be pulling fuel out at this area of the table.

    You moved the engine from one car to another, which means that you changed a bunch of things. I'd at least look at all of those changes first since perhaps you damaged some wiring or now you have an exhaust leak or something like that. Open headers usually are a problem for a wideband at idle, so one easy test is to add collector extensions.

  4. #4


    Quote Originally Posted by andrewb70 View Post
    What does it do in Open Loop? Andrew
    Running it in Open Loop is a good test too. But if your base map isn't correct you'll need to be prepared to jump on the keyboard and arrow up or down to make the actual AFR match your Target AFR. It's a good exercise to do, especially with open headers. If you can tune the base map in Open Loop so it's correct with the headers, then when you put in Closed Loop both CL Comp & Learn should stay small.

  5. #5


    Can you post the datalog & tune?

  6. #6


    Quote Originally Posted by allan5oh View Post
    Can you post the datalog & tune?
    We put it on a dyno and turned up the Learn to 40% and it started following the commanded AFR.
    Also, found I had injector flow rate and scaling mixed up with a smaller injector. Thanks!

  7. #7


    Yeah, if you turn off Learn, or make the Compensation Limits too low, then no surprise that it doesn't Learn. You have to be smart enough to not shoot your own foot off when you program an EFI system.

  8. #8


    If you needed to open it up that much to get commanded AFR, that means your tune is way out. Either the Base Fuel Table or corrections. Tune the Base Fuel Table in typical conditions fully warmed up. I like to inhibit Learn just below the thermostat rating. On a well tuned engine it should follow commanded AFR at all times with Closed Loop never more than 2% or less than -2%. There are some exceptions to this, but that's an advanced topic.

  9. #9


    Different people use different tuning strategies, but I agree with the above approach. I also like to have my Base Fuel Table match what the engine wants. I think I have a good fuel map with CL Comp and Learn are both in the single digits at all times. Other people don't care. They just let the computer adjust for a generic Base Fuel Table. Either will work since the computer can quickly do the map and make the compensation, but personally I prefer to have a clean Base Fuel Table with low corrections.

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