na2t ran fine b4 conversion, now running so rich gas and white smoke out exhaust

  • #1

    na2t ran fine b4 conversion, now running so rich gas and white smoke out exhaust

    I'm close to finishing my 1986 na2t conversion after doing it for 3 years. I'm dying to finish it but I'm unable to figure out why it runs so rich that white smoke now comes out the downpipe and gas is dripping out. This was not an issue prior to the na2t conversion, and only presented itself after I finished. I'm 99.99999% sure the white smoke is from the massively rich mixture not burning well. It's POSSIBLE something magically fried and it's burning oil now but I find that hard to believe given I didn't touch or do anything that would have caused that.

    1986 300ZX NA 5spd, all donor parts came from a 1986 300zx Turbo automatic ECU, Injectors, Turbo manifold, Turbo swapped onto car. Using relocation pipe instead of crossmember swap
    • CHTS looked original. Replaced. With or without it plugged in the car runs the same. I'm getting Ohm readings testing directly from the ECU side of the harness.
    • ECU diagnostics complain about CHTS still, code 13
    • O2 sensor was known good before the swap. unplugging it made no difference in how it runs.
    • Swapping in the old NA ecu and it still runs like doodoo.
    • Pulling the spark plugs, 3 in a row were soaked in gas, didn't bother pulling the rest. conclusive that it's not a single injector sticking.

    It would be completely drivable if it weren't for the embarrassing amount of smoking and I'm very concerned that the unburned fuel will catch my engine bay on fire (open downpipe until I can justify the cost of an exhaust system)

    It drives but god is it too rich to do so without tearing up and killing 5 brain cells a second. It will be driving off a cliff if I can't defeat this.

    I'm offering beer or bong hits if you want to give it a shot at my place in Bellevue, WA. Thanks for anything!
    Last edited by drnict61; 07-25-2018, 08:56 PM.
  • #2
    if the plugs are wet check your FPR, or just put in a new one for what they cost.

    you might want to make real sure you're using the right O2 sensor. I can't remember if it was just 86s in general that had the different O2 sensor than the rest, or if there was an NA/Turbo difference too. never had to deal with 86 hardware.

    white smoke on a new NA2T still sounds to me like turbo seals, but you're the guy with the car in front of ya. also if you're pulling spark plugs check the compression while you're there…
  • #3
    I thought heavy white smoke meant coolant in the combustion chamber, not excess fuel. That's usually black smoke.
    --------------
    Legal stuff:
    **Nissan Employee**
    Any information shared is simply my own opinion and NOT the opinion of Nissan

    not legal stuff:
    '88 300ZX 2+2-- driving… just details left
    '22 Q60RS-- I tell the wife it's hers…
    '87 Chaparral bowrider-- the next project
    '00 Corolla-- kids car.
    '14 E-350-- Gotta haul those kids in something.
  • #4
    White smoke can also be post-combustion oil, like an oil leak in the turbo or real bad blow-by.
  • #5
    Originally posted by FrozenZ View Post
    if the plugs are wet check your FPR, or just put in a new one for what they cost.

    you might want to make real sure you're using the right O2 sensor. I can't remember if it was just 86s in general that had the different O2 sensor than the rest, or if there was an NA/Turbo difference too. never had to deal with 86 hardware.

    white smoke on a new NA2T still sounds to me like turbo seals, but you're the guy with the car in front of ya. also if you're pulling spark plugs check the compression while you're there…
    My understanding of how the FPR works, in idle it's restricting flow, and only when there is vacuum/boost will it start to add fuel pressure. I think it makes sense to blame it but I don't have any fuel coming out the vacuum line for it. They are dirt cheap so might as well.

    I started with an oem nissan turbo, but it does the same thing without the turbo on it. Got a new turbo anyways cause it was kinda junky and I was not gonna get any sort of exhaust to hook up to it with it being relocated and using the stock hot side.

    redz31's site had a great chart on what ecus, injectors, and o2 sensors each year used and had interchange information. I specifically went with the '86 turbo ECU and injectors because I would not have to swap out the o2 sensor (titania) and I wouldn't have to do anymodifications to make the injectors play nice. http://redz31.suomiz.net/pages/fuel.html

    Looking at the smoke issue, it smells straight up like a rich mixture and nothing like burning coolant or oil. It's white smoke, not terribly thick. I also currently don't have any coolant OR water pump belt hooked up so there's no way it's still burning any coolant. The downpipe will spew fuel everywhere
  • #6
    "Pulling the spark plugs, 3 in a row were soaked in gas"

    well ,,,, I'd check your spark and timing again … or you have a mismatch ecu- injectors … or the fpr is screwy .... .( check the vacuum port to see no fuel is being blown thru .. that engine is getting extra fuel from somewhere )
  • #7
    Originally posted by dbruce View Post
    "Pulling the spark plugs, 3 in a row were soaked in gas"

    well ,,,, I'd check your spark and timing again … or you have a mismatch ecu- injectors … or the fpr is screwy .... .( check the vacuum port to see no fuel is being blown thru .. that engine is getting extra fuel from somewhere )
    I'll check spark and timing. Injectors need to be pulled for testing too

    ECUs match fine. It came from an 86 turbo. Problem persists if I swap the old ECU back in.

    FPR WAS new when I replaced it 3 years ago before parking the project. No fuel in the vacuum line though
  • #8
    When you turn on the ignition and the fuel pump runs … does it stop running ( ie pressure cutoff ?) If it keeps running , then you have a problem ..
  • #9
    Originally posted by dbruce View Post
    When you turn on the ignition and the fuel pump runs … does it stop running ( ie pressure cutoff ?) If it keeps running , then you have a problem ..
    Fuel pump does go off after a few seconds.

    After redoing
    -injector harness and plugs
    -spark plugs
    -spark plug wires
    -all grounds going to intake plenum
    -chts and harness

    And
    -plugged up ALL vacuum leaks, there were a few including IACV, some under throttle body, and pcv
    -changed oil cause it smelled like gas

    Drove it around for a few minutes and all issues cleared up. Been driving it daily the past few days and no issues remain. I blame CHTS at first, along with spark plugs, then from it running so rich previously it got gas in the oil thinning it out causing it to burn easily.