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Thread: !!!Exhaust is burning my eyes

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    Default !!!Exhaust is burning my eyes

    Hey everyone, my 77, which is bone stock, burns my eyes on deceleration while in gear. The exhaust fumes are so bad that they burn my eyes, but this is only with the drivers side window down and only while decelerating in gear. Anyone have thoughts as to what may be causing this?

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    Sorry guys, it is stock except for a Borla muffler

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    It could be coming from your gear shifter boot. Under the leather one there's a rubber one that can get loose and open up a big hole. I don't remember but you might have to remove the console, but it's easy, few screws in the armrest compartment and some more up front in the foot wells. I just remembered, after a swig of coffee, you will have to remove it. The leather boot is held down with some metal clips under the console. Good luck finding that leak, it could be dangerous as was pointed out to me by a fellow member who said a late night drive with the fumes could turn into more than a stinking problem.

    More coffee; you could use a flashlight to shine up or down around the boot then climb under your car and look for the light shining through. Just a thought.
    Last edited by siteunseen; 05-07-2013 at 02:12 AM.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Default muffler tip

    Quote Originally Posted by bryand2 View Post
    Hey everyone, my 77, which is bone stock, burns my eyes on deceleration while in gear. The exhaust fumes are so bad that they burn my eyes, but this is only with the drivers side window down and only while decelerating in gear. Anyone have thoughts as to what may be causing this?
    Easiest is to keep the windows rolled up and the fresh air vents on each side open.
    extend the tip of the muffler past the back of the bumper.
    replace the back hatch inner weatherstrip.
    replace the tail lite to body gaskets.
    check/replace the rubber body plugs near the muffler on the underside of the cars quarter panel.
    take the hatch upholstery panel off and tape/silicone a plastic over the opening. then replace the
    panel. lots of gasses come in thru the hatch lock.

    install a rear spoiler some people say it helps a little.

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    Occurs when you have high manifold vacuum. That's why it only happens when decelerating in gear.

    Higher the RPM the worse it is, right?
    How's your compression? Do you use oil?
    Is your BCDD working properly?

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    Registered User madkaw's Avatar
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    EGR working? I'm with Mr. Obvious, somethings not working with your EVAP or emissions controls.
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    that was my thought, maybe egr malfunctioning, I did discover today that the little vacuum delay valve is not working properly, its supposed to be easier to blow in one side than the other and was equally easy on both sides, im not sure i that would make the egr stay open all the time or closed all the time? As to the other comment about having high manifold vacuum, I was running a bit rich and I dont rem where I read that improper mixture affects the manifold vacuum, is it rich=higher vacuum or rich=lower vacuum?

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    Quote Originally Posted by Captain Obvious View Post
    Occurs when you have high manifold vacuum. That's why it only happens when decelerating in gear.

    Higher the RPM the worse it is, right?
    How's your compression? Do you use oil?
    Is your BCDD working properly?
    Yes its worse the higher the rpm is, my compression is good, do I use oil? and i know the bcdd is working, but I am not sure if it is adjusted properly, the douche at the smog station messed with it about a year ago and despite reading the FSM, I am not sure how to adjust properly

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    Well it sounds like you run very, very rich when you coast at high RPM. So rich, in fact, that you're beyond a mixture that will ignite and you're pushing clouds of atomized gasoline mixed with motor oil out the tailpipe. So you should look for things that would add fuel or oil to the party.

    Worn rings, valve seals, and maybe a specific kind of head gasket failure could all offer oil.

    Non-functioning or improperly adjusted BCDD or AFM could encourage extra fuel. So could a faulty FPR, leaky cold start valve, or injectors.

    But of all the items listed above, the BCDD is the one that is supposed to help with exactly that kind of "extra rich mixture at high manifold vacuum" emissions, so that's where I would start.

    You familiar with the carbs used on the earlier Z's? If so, think of the BCDD as the fuel injection equivalent of the older throttle opener servo that pulled the throttle open when you coasted. The BCDD essentially does the same thing.

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    I am having this problem... what is BCDD?

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    I would be more concerned about the fumes getting into the car, not what is causing it. You dont want carbon monoxide poisioning.
    When you have the window down it changes the air flow through the car and actually can cause negative pressure. This will draw air in from all places that are not sealing.
    I would check the hatch seal and sealing around the taillights etc. Then move onto the rich running problem.
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    Z_lis, 240s won't have BoostControledDecelerationDevice, BCDD, unless you have EFI for fuel delivery. Google it.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    I don't quite know what to do... my 76 had this problem, sold it, I finally got a 73 240, I love her so much, but just the other day I drove her to work and by the time I got home I was sick! I've replaced the tail light gaskets, the hatch is super tight (I'm going to paper test it again tomorrow) my firend put a new gasket aournd the hatch... the piece of vinyl that is on the upper hatch is loose... I'll fix that up tomorrow, got a muffler. I just don't want to get rid of her. I like the smoke bomnb idea. It's so bad, I know some one has figured out this problem... help!!

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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    A small leak into the car can be enough to fill the car with fumes. Zeds are known for it. I would start by checking the following:
    1: Hatch seal and alignment.
    2: Taillight gaskets and the grommet for the numberplate light. (the grommet can be too big for the cable)
    3: Fuel tank piping. Especially the small ones that the grommets are good.
    4: The frame rails in the car that go forward from the taillights. There is a grommet just behind the frame for the deck. Check all the screws are in the rail. I had this problem and these grommets are what was causing it.
    5: Extend the exhaust pipe and check it for leaks.
    6: Fit a BRE spoiler.

    Dont think things are OK. Check it to be sure.
    Chas
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    Registered User Stanley's Avatar
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    Z_lis my 73 had exhaust leaks from the rusty air galley, that goes from the well-named smog pump to the exhaust manifold, in three places - all where they couldn't be seen. Cut the air galley off inside the manifold and welded it. Better but still had another leak that went away when I had a new tailpipe and muffler installed.

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    Quote Originally Posted by Captain Obvious View Post
    Well it sounds like you run very, very rich when you coast at high RPM. So rich, in fact, that you're beyond a mixture that will ignite and you're pushing clouds of atomized gasoline mixed with motor oil out the tailpipe. So you should look for things that would add fuel or oil to the party.

    Worn rings, valve seals, and maybe a specific kind of head gasket failure could all offer oil.

    Non-functioning or improperly adjusted BCDD or AFM could encourage extra fuel. So could a faulty FPR, leaky cold start valve, or injectors.

    But of all the items listed above, the BCDD is the one that is supposed to help with exactly that kind of "extra rich mixture at high manifold vacuum" emissions, so that's where I would start.

    You familiar with the carbs used on the earlier Z's? If so, think of the BCDD as the fuel injection equivalent of the older throttle opener servo that pulled the throttle open when you coasted. The BCDD essentially does the same thing.
    Just to specify, you say I may be pushing clouds of atomized gasoline mixed with oil out the tail pipe, the only problem is if there were worn rings or valve seals there would be smoke, and there is not. There is also no coolant in the oil or vice versa to indicate a head gasket leak. As far as I understand the BCDD, it has nothing to do with mixture at high manifold vacuum, it only prevents the idle from dropping too quickly on coast and between shifts.

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    Quote Originally Posted by bryand2 View Post
    Just to specify, you say I may be pushing clouds of atomized gasoline mixed with oil out the tail pipe, the only problem is if there were worn rings or valve seals there would be smoke, and there is not. There is also no coolant in the oil or vice versa to indicate a head gasket leak. As far as I understand the BCDD, it has nothing to do with mixture at high manifold vacuum, it only prevents the idle from dropping too quickly on coast and between shifts.
    A reading from the book of FSM:

    "The Boost Controlled Deceleration Device (B.C.D.D.) is employed to reduce HC emissions during coasting."

    EC-5 - 1977

    As for the smoke... When you are coasting at high RPM, the cylinder vacuum is much higher than it is under other conditions because you are pulling high RPM against a closed throttle plate. Under these intermittently very high vacuum conditions, you'll pull more oil into the cylinders, but you won't see smoke because you're not burning it. You're pumping it out the exhaust without burning it.

    I'm just applying theory here trying to help. You asked for it.

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    Quote Originally Posted by Captain Obvious View Post
    A reading from the book of FSM:

    "The Boost Controlled Deceleration Device (B.C.D.D.) is employed to reduce HC emissions during coasting."

    EC-5 - 1977

    As for the smoke... When you are coasting at high RPM, the cylinder vacuum is much higher than it is under other conditions because you are pulling high RPM against a closed throttle plate. Under these intermittently very high vacuum conditions, you'll pull more oil into the cylinders, but you won't see smoke because you're not burning it. You're pumping it out the exhaust without burning it.

    I'm just applying theory here trying to help. You asked for it.
    Thank you captain, but remember that I am only experiencing this while decelerating in gear, If I am coasting in neutral I do not experience the burning eyes

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    Does anyone have any more ideas as to why I am experiencing this only while decelerating in gear?

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    What RPM are you talking about while decelerating?

    The ECU also has a fuel cut function, from 3200 to 2800 RPM on the way down. Page EF-12.

    The BCDD's purpose is HC reduction (EC-5). Not idle control. It's not clear how though, the FSM just says it's for "maintaining manifold vacuum at the proper operating pressure". Maybe to provide extra air to allow proper burning of any fuel injected. Implied by the word "operating" in the FSM description.

    I'm glad this came up because I've been catching one sharp whiff of unburned fuel right as I stop. Noticeable since it's warm now and the windows are down.

    Off to check the BCDD...

    Edit - just realized what that one connector with the plug in it is for, up by the coil. It's the BCDD, and maybe other, "function test connector". Looks like a pain.

    Edit 2 - the instructions in the FSM for checking the BCDD are confusing. Check resistance and voltage on the same circuit at the same time. Might take more thinking.

    Edit 3 - I think that instructions in the FSM for the BCDD are incorrect up to 1978 (says that 0 volts is good for everything - incorrect). The 1979 FSM has a whole new test procedure with new diagrams and a chart. That makes sense.
    Last edited by Zed Head; 05-13-2013 at 06:44 PM.
    1976 280Z, with some minor modifications

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    Quote Originally Posted by bryand2 View Post
    Thank you captain, but remember that I am only experiencing this while decelerating in gear, If I am coasting in neutral I do not experience the burning eyes
    I didn't say anything about coasting in neutral, and neither did the FSM.

    In the FSM, when they say "The Boost Controlled Deceleration Device (B.C.D.D.) is employed to reduce HC emissions during coasting." They aren't talking about coasting in neutral. By "coasting" what they mean is "moving down the road with your foot not on the gas pedal". In other words, "Letting the wheels drive the engine instead of vice-versa."

    Question - What's the difference between "coasting in neutral" and "idle"?
    Answer - Nothing.

    No Duh, you don't get the problem coasting in neutral. That's because you're "idling". You happen to be "idling while your car is moving", but your engine doesn't know it's moving... As far as it's concerned, it's at idle.

    Quote Originally Posted by bryand2 View Post
    Does anyone have any more ideas as to why I am experiencing this only while decelerating in gear?
    I've got an idea... How about you vigorously investigate the suggestions that have been made so far and let us know what you find.

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    Quote Originally Posted by Zed Head View Post
    The ECU also has a fuel cut function, from 3200 to 2800 RPM on the way down. Page EF-12.
    Hey Zed, I'm sure you know this, but just wanted to make sure it was clear to everyone else.

    The fuel cut function kicks in anytime the RPM's are above 3200 and the idle switch portion of the TPS is closed. This can occur at 3200, 4000, 5500... Anything above 3200.

    And once the fuel cut function HAS kicked in there is some hysteresis such that it will not kick out until either a) the idle switch is opened or b) the RPM's drop below 2800.

    Maybe it's just me, but I found your description misleading. Made it sound like the fuel cut was only active in the band between 3200 and 2800, and that's not the case. It's anywhere above 3200.

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    My mistake, thanks for the correction.

    I wish they had extended the fuel cut to a lower RPM. I think that's a big part of why these cars tend to be gassy smelling. 3200 RPM is pretty high, even 2800 is. Regualr driving gives no fuel cut most of the time. My 95 Pathfinder, apparently, cuts fuel when the throttle is shut at any RPM if moving. They learned.


    p.s. to my other post - My BCDD and TPS both check out. I think that my AFM is a little bit funky and has an uneven enrichment curve. Not super relevant to the OP's problem. Enough about my car...
    1976 280Z, with some minor modifications

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    Reason for hidious fumes in my car: ANTENNA DRAIN HOLE. Direct acces straight to cabin. I closed it with plastic tube and soda can cap. No fumes.

    Located just above muffler.
    -72 240Z "Goldie"

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    Quote Originally Posted by Zed Head View Post
    I wish they had extended the fuel cut to a lower RPM. I think that's a big part of why these cars tend to be gassy smelling. 3200 RPM is pretty high, even 2800 is. Regualr driving gives no fuel cut most of the time. My 95 Pathfinder, apparently, cuts fuel when the throttle is shut at any RPM if moving. They learned.
    I'm not sure why they picked the fuel cut points they did, but I find it "harsh".

    By that, I mean... If you pull your foot off the gas at 3500 RPM and let the fuel cut feature kick in, the engine braking effect from 3500 down to 2800 is much more pronounced than if the fuel had not been cut off. Makes perfect sense since the engine is a complete load instead of supplying some power. In fact, once the RPMs drop and you hit the bottom of the hysteresis band at 2800 or so, you can feel when the fuel starts flowing again.

    However, I'm used to the "normal" engine brake coasting effect like what occurs in other cars, and the fuel cut induced "uber braking" above 3200 is uncomfortable. It's too steep of a curve and I'm glad they didn't do that everywhere.

    As for the Pathfinder... Is it automatic? In automatics, the engine braking effect is always smaller because there's slip in the hydraulic drivetrain. They might be able to get away with a full time complete fuel cut because the drive train slip will prevent you from feeling like you're gonna smash your face on the windshield every time you let off the gas.

    (Have we strayed far enough from the OP's question yet? )

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    Maybe just a little further

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