Leak down test - Air and smoke out of oil cap?

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  1. #1
    Member Shyzah's Avatar
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    Leak down test - Air and smoke out of oil cap?

    My engine is a ~100k mile 6MGE which sat for 10 years during 2006-2016. It ran fine for 5 months after I bought the car.
    I did a post a while back talking about how my 4th cylinder is not firing. It had 160 PSI of compression, fuel, air, and spark. Oil was getting into the cylinder and fouling the spark plug ( I believe). The spark plug would get covered in oil quick and the cylinder is also oily when I look down. After driving it a little, I am noticing a grey paste on the spark plug. I decided to do a leak down test and my gauge is garbage so I do not trust the reading. However, there was quite a bit of leakage coming out of the oil cap area. I heard it leaking (sounded louder than normal) and there was also smoke or something coming out. I did the same leak down test to other cylinder, and they had exactly the same result so now I am very confused. Why are cylinders that are firing just right also having the same result as the dead cylinder? I thought my piston rings might be bad but all the cylinder have around 160-165 PSI of compression. There is no air coming out of the intake, exhaust, or bubbles in the coolant in all cylinders.

    My initial thoughts were bad oil ring or valve stem seal causing the oil to come in and foul out the spark plug. Not sure what to do at this point, might give the car to a Toyota dealership to figure out.

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  3. #2
    CelicaSupra.com Member AJ's Avatar
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    I would try an oil change using a quart of Marvel Mystery Oil. To see it that will clean the piston and rings to provide a better "seal"...
    Regards,
    Arch
    '86 Supra MA67
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  4. #3
    CelicaSupra.com Member Khlause's Avatar
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    You're likely right about the oil rings, but that "grey paste" would make me nervous enough to pull the head and see just what is going on.

    Did your car sit for 10 years outside? Or was it garaged?.

    Can you post a picture of the spark plug?

    There is an easy to use and free image hosting site.

    https://m.imgur.com/

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  6. #4
    Member Shyzah's Avatar
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    The car sat for 10 years under a cover, outside, in a drive way in Southern California. The engine was swapped into it by the father of the guy I bought the car from in the early 2000s I believe. The guy got the car running again in 2016 and put some miles on it and then sold it to me in 2018. It ran like new for a 2000 miles. It started misfiring so cleaned out the clogged injectors. When I put everything back together I forgot to put the distributor in with the right orientation so the car wouldnt start. I kept cranking it and eventually it started, then I realized the timing was off. After correcting that, I noticed cylinder #4 was completely dead. It wasn't dead, or as dead, before. Heres a photo of the oily spark plug. I do not have a photo of the grey paste... The grey paste was mostly on the bottom threads of the plug.
    Photo #1 shows a dry plug before I put it in that cylinder.
    Photo #2 shows that plug after I ran it in the dead cylinder for a minute covered in oil. You can't see how bad it is due to the shade.
    photo #3 is a old photo of the dead cylinder before the grey paste started to appear.
    oil1 by Shyzah, on Flickr
    oil2 by Shyzah, on Flickr
    Cylinder 4 and plug for 4. by Shyzah, on Flickr

  7. #5
    Founding Member pdupler's Avatar
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    You are going to have some blow by even on a new engine and we aren't hearing what you are hearing so its hard to say, but if the numbers on the gauges are right, then its not a compression problem. An engine can be burning a "lot" of oil and still run perfectly smooth so I don't think oil fouling the plug is the problem.

    I may be way off, but just trying to reason this out so follow me for a moment. I am imagining a car that sat for ten years, maybe you got it to run for a while, but eventually a "chunk" of 10 year old congealed gasoline dislodges from somewhere after the fuel filter and wedges itself into fuel injector #4. You did say in the previous post that you found yellow flakes in the fuel rail. Maybe there's more where that came from. I could imagine a dribble coming out of an injector instead of a spray so no air/fuel mixing and thus no firing. Maybe instead liquid fuel is washing the oil off the cylinder walls and intake valves, splashing round the cylinder and onto the spark plug. Now imagine an oil/fuel mix like in a 2-stroke being partially ignited on the electrode but not explosively like its supposed to, rather more like a smoldering fire. Only its not ashless 2-stroke oil, its motor oil. So now you got oily, grey ash on the spark plug. Maybe the problem is still in the fuel delivery to Cyl #4.

    Or it might be similar symptoms if say the spark plug is only firing one out of every five compression strokes. If the fuel/air mix is not burning, then eventually it builds till its "wet" in the cylinder, washing the oil off the cylinder walls and same thing happens. Plug finally fires once after ten tries and because the plug is wet with a fuel oil mix, you get ash.
    Phil D.
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  8. #6
    CelicaSupra.com Member wagzilla's Avatar
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    the silver paste look like antiseize you put them on some of the sparkplugs

    James
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  9. #7
    Member Shyzah's Avatar
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    @wagzilla I didnt put any antiseize on the plugs. Ive been through 3 plugs on that cylinder and never saw that paste before. Just saw it after driving the car 6 miles to a car meet and back on 5 cylinders lol.
    @pdupler That's why I'm so confused... there is nothing wrong with that cylinder that would cause it to not fire. The valves were perfect from the leak down test. Maybe it is fuel delivery. Is there any way I can test the fuel delivery into that cylinder? I know the injector is good. Had them cleaned and tested by a company. Only thing I can think of would be, like you said, something in the fuel rail that is doing something. At the same time, how can something that large flow through my fuel rail and block off only one cylinder? Also, when I took the injectors out for the second time I ran a brush through the fuel rail making sure there wasnt anything large down in there.

    Do you guys think this could be a computer related issue?
    I honestly don't have any time to work on this thing with college and the last thing my parents need is my car torn apart in their garage for 3 weeks so maybe Ill just give toyota the $135 to try to figure out whats wrong with it?

  10. #8
    Boosting Mod SilverMk2's Avatar
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    Toyota is unlikely to even know what one of these cars even look like. Did you ever pull the valve covers to make sure the valve train is correct? You can easily check injectors by shuffling them around and seeing if the problem moves. Fouling the plugs from oil takes time so a new set of plugs should work for awhile. If you have a ring or valve stem seal problem the car should be smoking out the tail pipe. You'll get a bit of leaking since the rings aren't a perfect air tight seal.

    If the problem suddenly appeared after working on the distributor I'd suspect thing in the area, wires, caps, etc.

  11. #9
    CelicaSupra.com Member Zerodrag's Avatar
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    The grey stuff does look like antiseize compound. Looking at the pic you attached with the oily cylinder, I think you can see that same grey stuff on the spark plug threads. you may have brushed against the threads while installing/removing the plug?

  12. #10
    Founding Member pdupler's Avatar
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    Quote Originally Posted by Shyzah View Post
    Maybe it is fuel delivery. Is there any way I can test the fuel delivery into that cylinder?

    Do you guys think this could be a computer related issue?
    Seems like I remember someone posting on here about how they set up a rig to test fuel injectors so they could see the spray pattern and measure the flow. I'm sure there's probably youtube videos, but while its conceptually simple, that's spending some serious time to make a tool.

    It is possible that its a computer related issue as the computer controls the injectors, but it could also be a wiring issue. Maybe the wiring or connectors between #4 and the ECU is compromised somewhere. The wiring harness is surely quite crispy after 36 years and every time you touch it there is some risk. You'd need a simple noid light to check to see if the injector is getting signal.
    Phil D.
    85 Silver 6m-gte, completed 2000

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