Blue Smoke when leaving stop, help diagnose

Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by straws, May 15, 2011.


  1. straws

    straws New Member

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    Hey all,
    Just bought a 1992 Vert with a 2.3 for my daughter (First car). On driving it home my wife said the tailpipe was smoking blue when taking off from any stops and when I let of gas then accelerated.

    Does this sound like a valve seal problem, or a ring problem? If valve seals, can they be changed while the head is on the car?

    Thanks in advance.
     
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  2. madmike1157

    madmike1157 the humor is still lost on me SN Certified Technician

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    anytime you either lift off the throttle, or let a car sit at idle, vacuum is at it's highest. If the car smokes during either of these times (or both) Then the seals or valve guides are the culprits.

    While umbrella seals can be changed "on the motor" you'll have to pull the head to fix the latter.

    Smoking under acceleration, is almost always a sign of poor ring seal.
    Unscrew the oil fill cap while the engine idles and see how much smoke puffs out of that hole. Depending on how much smoke is coming out of there is an initial telltale that you have a worn out engine.

    If that looks bad, an engine leakdown gauge set is the next step, and it will tell you everything. The set is comprised of two gauges and a regulator. One side of the kit is screwed into a cylinder spark plug hole, the other side goes to the supply of compressed air. The regulator can be set to supply between 75-100 psi of air to that cylinder, (one gauge) and the other side gauge will detail the percentage of that cylinder leakage.
    in addition to the gauge reading 30% or higher (all bad) You'll more than likely hear air leaking both into the crank case and into the intake past the valve if the valves are not sealing properly.

    Obviously not something a shadetree mechanic has at his disposal, but maybe auto zone rents it.

    You could also use a standard compression tester to see how low the compression has dropped, and to determine whether there is a cylinder lower than the others. But unlike the leakdown kit, it will not tell you where the lower compression in a suspect cylinder is going.

    I brought home a 89 4 cyl notch last summer, and it smoked so bad when I decelerated, that a cloud of smoke would catch me if I came to a stop at a light.
    That engine is sitting in a corner of my garage now, waiting for me to decide on what to do w/ it.

    Your welcome in arrears.
     
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  3. straws

    straws New Member

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    thanks for the reply. I do have all professional tools at my disposal, I was just looking for a better opinion that what I suspected.

    There was an old rule of thumb: Cold blue smoke = seals, hot blue smoke = rings. But on another site, and older gentlemen gave me some really, really interested attempt to fix...if the rings are stuck. He said to change the oil with a good thin synthetic, and add 4 oz brake fluid, and 3 oz trans fluid. He says the brake fluid will swell the seals and stop the obvious leaks and valve seal issues, and the trans fluid will clean the oil ring and if stuck open them up. The obvious reminder that if done for a customer, you would not be in business too long. But I thought I would pass that on.

    This is kind or a mute point now, because Saturday I bought the 92 vert, and Sunday (today) I bought a 93 Hatch. The 93 was bought by the guy to convert to an 8 cyl, so I got the engine running again by reconnecting all the hoses and wires, and it runs real good. So disaster averted. I will swap the motors, and part out the rest of the hatchback.

    Thansk all
     
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  4. straws

    straws New Member

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    Fixed. So honestly since i have a parts car complete (bad title), I never tried to diagnose the car. My worst suspicions were pretty much confirmed in another chat group. Nonetheless I went to start pulling the motor, and guess what I found?

    When I disconnected the "cold air kit" I was going to replace from the parts car, I found the throttle body full of oil, and realized the bad oil leak (not mentioned here) was actually from the cold air intake where oil ran down the tube and leaked through the air filter, then through the frame rail.

    So long story short...the PCV valve was rusted stuck shut. THis caused the small breather line from the throttle body to reverse and let oily air flow into the throttle body instead of the clean air come from the throttle body into the valve cover.

    Whew...$2 saved me a TON of work. So now the car is ready to except a new muffler it needs.
     
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