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Thread: Running rich

  1. #1

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    Running rich

    Hi All

    So my car has suddenly decided to run a little rich. Was a fine a day or 2 ago.

    What used to the numbers

    Full deceleration > 20 AFR
    Idle/cruise 16-17
    Accelerating 13-14
    WOT 11

    Now

    Full deceleration > 20 AFR
    Idle/cruise 14-15
    light Acceleration 12
    WOT 9

    Defiantly seems to be consuming more fuel too.
    It never had a O2 sensor since I have owned the car. Do all vr4s have a O2 sensor?.

  2. #2
    elnevio's Avatar

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    To be honest, those new AFRs could easily be stock values. I've certainly seen loads of VR-4s dip below 10 on the dyno!

    And yes, all VR-4s have a single O2 sensor from the factory - located in the downpipes just before the cat.

    How has it NOT been running rich before now, without an O2 sensor - what sort of setup do you have? E.g. after-market ECU, remap, MAF delete, etc.?
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  3. #3
    Nick Mann's Avatar

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    As Nev says, the new numbers are close to standard VR4. And also as Nev says, the lambda sensor should be in the downpipe after the join and other than wot it controls the fuelling.

  4. #4

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    Quote Originally Posted by elnevio View Post
    To be honest, those new AFRs could easily be stock values. I've certainly seen loads of VR-4s dip below 10 on the dyno!

    And yes, all VR-4s have a single O2 sensor from the factory - located in the downpipes just before the cat.

    How has it NOT been running rich before now, without an O2 sensor - what sort of setup do you have? E.g. after-market ECU, remap, MAF delete, etc.?
    Factory ECU not sure about a remap.
    Factory MAF

    The AFR is brand new. The problem is I have seen it running perfect. Some thing has happened in the last day or 2 . It bogs down when afrs hit <12. The fuels seems to be coming early to the party.

    I bough the stock o2 sensor a year ago. but I always failed-to find the electrical connector for it . So never installed it. Was happy with performace until recently. The main area that has been effected a lot is cruise and light decelerate.

    can we think around the fact that it was perfect 2 days ago. what could have gone wrong? valves rings ?

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    is there a MAP sensor in our cars? how does the ecu measure boost ? If its the measure it through the MAF won't the air temp effect it?

  6. #6
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    There is no MAP sensor. The ECU does NOT measure boost or AFR (other than the narrowband, which is used only during part-throttle).

    All fuelling information comes from the MAF measuring the airflow accurately. The ECU has compensation for inlet air temperature and barometric pressure to determine fuelling.

    If your fuelling has suddenly changed, then it's a mechanical issue - start with the simple and "can suddenly change" things - an exhaust leak, a loose vacuum hose, a different air filter has been fitted, lower quality fuel. Don't go jumping to conclusions that it's something inside the engine.

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    I just added the O2 sensor back to car. will post the AFRs soon. EVO Scan in reporting my Throttle position value at 17% when not pressed and WOT at 97% should it be this way ?
    Last edited by iftekhar.frt; 17-06-2020 at 05:39 PM.

  8. #8
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    Quote Originally Posted by iftekhar.frt View Post
    I just added the O2 sensor back to car. will post the AFRs soon. EVO Scan in reporting my Throttle position value at 17% when not pressed and WOT at 97% should it be this way ?
    Usually shows 13% when TB is close, its normal with vr4s
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  9. #9

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    here are a few evo scan results after adding the o2 sensor back to the car and resetting the ecu. The o2 values seem to the oscillating a lot even on idle and are more inclined towards being rich.

    Had the car checked for boost leaks. Added better quality and new airfilter.

    https://drive.google.com/drive/folde...hQ?usp=sharing

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    I think the left one is the fuel pressure solenoid. What is the purpose of the knob with the Mitsubishi logo?

    F4A9317E-AAA4-4F1F-814F-FF36CA49CB4D.jpg

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    It's a filter and/or one way valve.

    This bleeds off the vacuum feed to the FPR during hot restarts to raise fuel pressure to aid cranking by opening the solenoid valve to atmosphere.

  12. #12
    Confused's Avatar

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    What air filter have you fitted? Hopefully a new panel filter in the original air box, and not a cone one!

  13. #13

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    Quote Originally Posted by Confused View Post
    What air filter have you fitted? Hopefully a new panel filter in the original air box, and not a cone one!
    yes a new panel filter. The O2 values seem to be oscilating between 0.1-0.9 volts. but the wide band is stable at 14.1 hot idle this used to 15.5-16

  14. #14
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    The narrowband oscillating like that is good - that means it's working properly to maintain the stoichiometric ratio for the current fuel blend.

    Remind us what wideband do you have, please?

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    if @iftekhar.frt had post up the AFR numbers in the first post and said what is wrong, i would have said you are running lean in all instances compared to factory standard setting by a 1 or 2 AFR's.

    but you are saying this is normal and AFR you have now which look normal to me are actually rich. so you see why people are asking the questions they.

    you car was not running factory standard AFR's originally so some must have been done to the car to make it run leaner. if you can pinpoint what that was it is probably a good bet that whatever it was that was fitted to the car to make it run leaner has failed.
    but garry' line of questions is going to narrow down the issues you are having. and you have to narrow it down bit by bit until you get to the actual cause.

    Bye for Now!

  16. #16

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    Quote Originally Posted by Confused View Post
    The narrowband oscillating like that is good - that means it's working properly to maintain the stoichiometric ratio for the current fuel blend.

    Remind us what wideband do you have, please?
    https://www.amazon.com/AEM-30-0300-W.../dp/B0184TSI84

  17. #17

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    Can this be some sort of an electrical issue. The only electrical mod to the car is that battery has been shifted to the trunk. Then again it was done about a year ago.

    I just went out for some groceries and surprisingly it was running as i wanted it to, i.e. cruise at ~16 hard pulls ~11. but on my way back the problem came back idle at 12 and light pull 9-10. The same sensor is giving the correct values on my other car.

    It really hot here too since the last 2 weeks like 42C could that doing some thing.
    Last edited by iftekhar.frt; 23-06-2020 at 10:53 AM.

  18. #18
    Davezj's Avatar

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    is there a temp releated compensation table in the ECU that will change the AFR? i am not sure but there are lots of temp compensation table inthe ECU. just a thought.
    to be fair i would have suggested that the ECU has been reflashed at some pint to lean out the AFR's as i can think of what would make all your AFRs lean on a regular basis. apart from an ECU reflash.

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    So this is how the o2 sensor values look ploted overtime. I don't think this is correct. This whole time the car was warm and idling around 1000.

    Screen Shot 2020-06-23 at 3.49.53 PM.png

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    Although the car is idling does so much change in AirVolume make sense ?

    Screen Shot 2020-06-24 at 2.08.53 AM.jpg

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