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Thread: Engine runs rich, can`t pass emissions.

  1. #1
    Senior Member
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    Tore Daniel
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    Default Engine runs rich, can`t pass emissions.

    Hi all!
    It`s that year again where I have to pass emissions with the darned wagon.
    Figured this would be a piece of cake compared to the 2T engine I had in it before, alas....
    I did bring this problem up at aeu86 forums also, but after they requested swap ECU or harness or something for the third time or.. something.. without it making a difference as far as my problem is related, the topic kinda fell dead quiet there, so figured maybe someone here can throw a fresh light on things if they feel like it


    Car: 4AGE Swapped TA40 Zenki Wagon.
    Engine: Stock Early MAP AE86 EDM Bluetop Bigport 1983-1984 Non-O2/OX(whatever everyone calls them) Non-Cat 16v 4A-GE.
    In other words, Unlike the Early JDM and USDM Bluetop Bigports this engine has a OEM, Fabric installed, 100% stock variable Resistor A/F adjuster (What we call Potmeter) in place of OX/O2 sensor and Cat and all that shaite.
    (^They switched to O2/OX+Cat on Late EDM Bigport AE86 motors)

    Problem: Runs way rich to pass emissions, 0.8 Lambda should be 1.0, 6,5 to 8,1 CO% (Not CO2, CO, since this is non-O2 non-cat 4A-GE), but not rich enough to impede coldstart-idle-driving.
    It has to be below 4,5% CO (Stock TA40 2T) to pass.
    In laymans terms, it`s overfuelling with 20%

    Tried:

    Firstly all the timing stuff, resistance through plugs+leads+dizzy cap, all multimeter resistance (in ohm) values within spec on TWO different multimeters (And ALL components of which are brand new)
    Resistance on stretched leads are within specs.
    Plugs look fine, nice and red/brownish where ignition spark goes, slightly sooted everywhere else.

    Ignition timing spot on at 10 BTDC (In Diag mode).

    Timing belt (New) TDC 0>Lines up with crank (which also lines up with oil pump).
    Timing belt tensioner is new.
    Water pump is new.
    Thermostat swapped 3x.
    All water connection necks, pump etc etc gaskets are new (Even new O-ring at block where water pump is mashed up against it).


    As far as stuff I`ve done during all the emissions inspections I`ve been trying to get it through these past couple of months:
    (Made no difference = I tried it at home without getting confirmation at inspection workshop, but still without visible decrease of obvious Fuel Rich exhaust smoke and odor).
    (Made xx% Difference = Have checked it out at inspection workshop and have emissions computer values to back up my observation).

    Made a new exhaust (1,75 or 2" I believe) new center muffler, new rear muffler, new piping, new gaskets for the whole sheblang (Made 0% Difference)

    Swapped the half-ass repaired green ecu water temp sensor at the back of the head (Made no difference.)

    Checked Injectors, they are the correct type (182cc).
    Swapped Injectors for similar ones (Made no difference).

    Adjusted on the stock A/F potmeter, (Made 0,3% Difference, Out of 8,1 total..).
    Swapped A/F potmeter for non-OEM type, (Made 0,3% Difference).
    Swapped A/F potmeter for another OEM type (Same P/N) (Made 0,3% Difference).

    Installed Tomei FPR Type-S, adjusted to minimum factory fuel pressure spec, (only affects 0,3% CO)
    Swapped wiring harness 2x (Made no difference).
    Swapped ECU 3x (All same P/N, all belonging to this specific setup, Made no difference).
    Swapped Coil 3x (Same P/N blabla, no difference)
    Swapped Igniter 3x (Same P/N and Yeah you know)
    Swapped radiator (thinking maybe coolant got too cold, made no difference).
    Swapped for pure water in cooling system (to heat it up further and affect the sensor, made no difference).
    Swapped Cold start injector 3 times, disconnected Cold start injector etc etc you name it, Made no difference...

    And of course I`ve checked Battery (which is new), holds charge, holds starting amperage.
    Alternator charges nicely, alternator sense wire is good, alternator Ignition wire is good (tested criss-cross across france with multimeter).
    Compression good, compression difference within OEM FSM spec (10 psi difference whereas OEM FSM spec states 14 psi).

    The reason I had to swap ECU 3x according to aeu86 is because I cant get ECU into diagnostic mode (W-pin #13 on Body Harness Connector at ECU) all of them removed from cars working perfectly passing emissions and the whole shaite before they got to me, Lamp positive on W-pin, Lamp Negative on Earth, nothing, not one blink..
    ^On Totta`s request I tried the same with half throttle, not one blink.

    Been looking at TPS but it`s lined up with some small scratch marks, Did unscrew the screws a bit and twist the TPS around with engine running, and it promptly ran like shaite at any given setting so I wisely (I suspect) lined TPS back up with the scratch marks, but we did twist it around a little at inspection too, maybe 0.1 degree turn at a time, ZERO impact on emissions (but ran like shaite) just so thats said.
    ^I could swap it, and in the process have to dismantle the whole cooling system AGAIN so honestly at this point I just can`t be bothered unless it can be proven beyond a doubt that it has to be done...

    The oddest two things is when the engine is cold, theres barely any smoke or odor out of the exhaust (when the engine is in closed loop mode I guess).
    When the engine heats up (and switches to Open loop mode I believe, or if these two are the other way around, WHATEVER) the smoke just bellows out of there and smells rich as hell.
    ^ Despite all this, it drives like an absolute champ, doesnt miss a single beat, starts every time on first crank, throttle response OUT of this world insane.
    ^ Can`t pass emissions.

    Any ideas other than what I have already mentioned and tried are appreciated
    Last edited by Tore; 15th May 2016 at 07:24 AM.

  2. #2
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    bazz
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    Default

    Put a big cat. Or 2. I used a big v8 cat once. Did the trick. Mate then used the same cat and added it to his existing cat and it passed emissions.


    Sent from my iPhone using Tapatalk

  3. #3
    Senior Member
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    Tore Daniel
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    Default

    Thats actually one solution I`ve been considering for a while now, but not working on the issue for a couple of days have cleared my head, I still have some things to check out.
    Primarily, the EWD 4A-GE manual from aeu86 states belt timing should be TDC0 for cams and BTDC 5 for crank, I may, not sure, but I MAY have messed that up (TDC0 cams and BTDC0 Crank).
    ^ If that`s not the issue then I`m probably still looking at a internal engine issue, head might need a simple servicing (valve seals+HG+bolts).

    Will check it all out within the next couple of days and update as follows

  4. #4
    Senior Member
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    Tore Daniel
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    Default

    Yep, figured it out..
    I noticed on wiring diagram, the pin-out for the ECU, Pin #8 theres a wire called VAF (On Early EDM 4A-GE`s) that goes to cold start injector and shit, then on the EFI diagram it shows the CO Variable Resistor (The potmeter for adjusting A/F) as having a VAF pin too, Black wire with Red Stripe, the body Cold Start harness (Why would they put it there??) ties in somewhere at the Engine wiring harness close to the firewall in the engine bay.
    So I installed a wire between VAF at ECU and directly to the Black and Red wire at the potmeter, voila!

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