3800 Did I blow up my engine?

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A

alexgtp

TCG Elite Member
Aug 3, 2007
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  • #1
    Well for the past two days . When I have started my car the car seems to be choking because of too much fuel. The 02's are pegged at .999 and the car starts to bog and choke like it wants to shut off. After revving it and running the car the car seems to run good again. Well yesterday I had the same problem. But I decided to drive out to pictors shop anyways.
    Well I got some new tires and sway bars in. But here is my problem.


    Yesterday I was driving home on 294. I went to WOT and than I heard a very scary sound ..The same sound Jareds car made when he blew his pistons.. A real loud bang and than the sound of metal jumping around in the engine and than that sound of it traveling thru the exhaust.. I pulled over at the nearest rest stop.. started the car up again and listened to the car. Well it sounded fine.. NO mis-firing...no metal on metal sound..no tapping of the rockers.. nothing. The exhaust note sounded very good.

    So I drove her home no problems. This a.m. I go to check the engine for physical signs of damage. I started thinking maybe a bolt came loose and bounced around in the engine and that was the noise I heard.. But everything checked out. So I start the car this a.m. and it did not choke and bog at all the o2's looked normal. The car idled nicely I drove to work this a.am and everything looks great.


    1. What the hell happened to the car?
    2. If I blew anything.. WOuldnt I of thrown some sort of code.?
    3. Why is the car running better now?


    Ughhh.. :(
    Click to read more...
     
    gtphale

    gtphale

    TCG Elite Member
    Nov 9, 2008
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    Aurora
  • #3
    Welcome to the blown piston club. I guarentee that you blew the top of a piston off. Luckily it went through your exhaust and seems like it didn't do any damage to the heads. Could of been like Pictors. Time to get a new piston and drop the pan there is a few differant ways to fix this but don't leave it the way it is just cause it sounds ok now. It will continue to fall apart and can do some serious damage.
     
    gtphale

    gtphale

    TCG Elite Member
    Nov 9, 2008
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    Aurora
  • #4
    I have a compression tester.Not sure it would help though. Inorder to lose compression don't you have to have a bad head gasket, rings, or scored cylinder???Not sure just asking, Alex pull your plugs and look at the electrode to see which is bent cause i'm sure one is. That will be the cylinder that has the bad piston in it. I bet your kr was really high even at idle when you blew the piston up. Did you install that iccu yet? Were you playing with the timing?
     
    M

    Mike K

    TCG Elite Member
    Apr 11, 2008
    13,214
    2,586
  • #6
    What mods are on this car?

    It seems very unlikely that you would exhale a chunk of piston without doing valve damage and still have a good running, good sounding engine.

    Keep in mind that a motor running that rich probably has fuel saturated oil, which doesn't aid much in the lubrication process.
     
    A

    alexgtp

    TCG Elite Member
    Aug 3, 2007
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  • #8
    Yeah I did not have a chance to pull the plugs. funnt thing is I just put in new plugs yesterday. I will check during lunch :).. Hmm about the compression check. Will a cracked piston cause lower compression?

    LIke I said Iat WOT I am seeing anywhere beyween .999 and 1.2 o2's and KR around 4-5... D'OH!!

    Mike my thought ecaxtly.
    I know what a cracked pistion sounds like I have encountered that numerous times. I remember JAreds car when we started it up again.. it sounded like a helicopter.. with metal slappiing metal..

    My initial thought was a broken spring.. but no misfires..
     
    horist

    horist

    Geek
    Nov 10, 2008
    2,031
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    Lake Zurich
  • #9
    well... if a chunk of piston is missing (or even if there's a small crack) you'd be having some big time blow by issues... so when you pull the dip stick is the oil on it airated (sp)? (tiny air bubbles mixed w/the oil)

    Does oil spew outta the dip stick? (I'd think w/a missing piece of piston even ifit's small you'd have so much blow by it'd be forcing oil out anywhere it can go)

    Also... not sure if GPs have an engine sensor fuse... but if so check that.. if it blows it will disable the MAF so the car runs in speed density I believe... this could cause it to run really rich... so maybe it was a rich back-fire? (any PO102 or similar codes being set? on my F-body the MAF and O2 heaters are on the same circuit)
     
    B

    beyerch

    Addict
    Jan 20, 2009
    704
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  • #10
    contrary to public believe you can definitely blow a piece of piston and the car will still function. I have seen this numerous times. We acutally had a car in california on a dyno running it to 155 MPH with a blown piston! It really just depends.

    Are you sure you didn't hear a big backfire? With all that fuel maybe it had a huge ass backfire and shot out a big boom! Were you accelerating or decelerating when this happened ?

    As far the o2's, my car did that when the MAF sensor died. If you disconnect the maf sensor, the pcm will run on default tables and that hsould at least allow you to eliminate that from the equation. The thing to note is that you should not POUND on the car without the maf sensor. The "deafult" tables were calibrated for a bone stock car and were never meant for a heavily modified car, etc.

    The other thing I would check is the wiring to make sure nothing "mated" with a header. I've seen wiring end up getting too close and cooking itself.

    If you need anything else maybe you can bring it by one night; however, i'm way behind with people already due to family being sick, work, and now i'm sick!
     
    R

    rob

    TCG Elite Member
    Dec 28, 2008
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  • #11
    .....Your right the plug condition should tell you a little sooner....Lets just hope a valve or seat didnt get damaged.... Or worse a cylinder wall. I did enough damage too knock my compression down but still didnt damage the wall. Thats all I ment.
     
    1

    12secGTP

    Addict
    Nov 10, 2008
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    Des Plaines
  • #12
    had (and still do at times) of the problem of the high O2`s.
    my problem was (and still is) that I did melt some wires on the header. this causes the intermittant prob with the O2s. Goes away after the car warmed up.

    sucks to not know if you have a blown piston or not. I am still wondering from last year myself. Guess I will find out for sure when I do the cam this month....

    if a small piece cracked off, a compression check will not tell you anything. the amount of compression lost would not be enough to measure (unless the WHOLE top of the piston was gone...)

    I am not really sure you would have any blowby issues unless a ring is damaged, or the cylinder walls are scored pretty bad. the top of the piston does not seal against the walls, the rings do.

    the only real way to find out is to pull the heads or get a bore-scope. I have yet to find one of those... well, I did find one but it was 700$... :(

    hopefully the engine is ok... if you need a hand with anything, let me know.
     
    A

    alexgtp

    TCG Elite Member
    Aug 3, 2007
    2,272
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  • #13
    Well I just pulled the plugs. They look pristine. NO damage to any of the electrrodes and they are still gapped at what I gapped them at yesterday.

    No air in the OIL. Oil looks good. Hmm so what happened. Maybe I did do a massive backfire. But I have never heard a backfire sound metallic.. Well I guess when I do the heads and cam I will see if I have a blown piston.

    Thanks guys for all the suggestions.
     
    S

    sr71_rgl

    Guest
  • #15
    Originally posted by alexgtp@Mar 1 2004, 12:39 PM
    Well I guess when I do the heads and cam I will see if I have a blown piston.

    Thanks guys for all the suggestions.
    Click to expand...
    Charles is right about motors running well after loosing a piece of piston. I can't recall the guy on clubgp that made several mid 12 sec passes with pieces from 2 pistons missing before it eventually broke off a huge piece which killed compression. You probably did lose a chunk of piston but consider yourself lucky that it blew out so fast. If you keep your boost levels at what they are now :rolleyes: you shouldn't have anymore problems. Prepare to do what hale said if you're going to up the boost at all. Good luck.
     
    R

    rob

    TCG Elite Member
    Dec 28, 2008
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  • #16
    Their are many ways you can do this job.......He indicated that the car was running reasonably well dispite the readings which MAY indicate that he still has good compression and he didnt.....

    -Damage the piston or rings enough to cause blow by through the piston.

    -Bent, nicked, or damage the valve or seat causing a leak.

    If he has good compression or is not leaking down out the crankcase,intake, or exhaust with both valves closed he is a perfect candidate for what Hale suggested or changing the piston from the bottom. If there is an idication of blow by it is a topside job............

    Borescope is nice......Think I can find one for $400......I think thats what Hale charges to put a piston in though........A compression tester/leak down is much more economical..... and too be sure....Your not going to see a bent valve or dam seat with a scope.
    I want to help with my suggestions as much as everyone and am not saying this is the ONLY or RIGHT way to do this....Just trying to help....And all I mean is this is the way I did it..
     
    H

    htsht

    Member
    Jan 23, 2008
    22
    0
  • #19
    When I blew mine it was very simialar sounding to yours. Made a loud backfiring sound but then no ticking nothing after that. Car ran fine. The 02s were all over the place. Pulled the heads just to check things over. Was a good reason to talk the wife into a p/p job on the heads.:lol: Sure enough the #3 piston had a big chunk blown off of it.
     
    gtphale

    gtphale

    TCG Elite Member
    Nov 9, 2008
    1,578
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    Aurora
  • #20
    Yea there are alot of things that could of gone wrong. I would still pull the heads out if I found out it was a piston causeI would want to see the walls and then clean them. Forgot tech. wording for it.lol

    Also make sure that the ceramic is ok cause when I blew mine the prong was ok but the ceramic was cracked off. I'm sure the walls are fine cause our pistons are so soft compared to the walls.I think Zoomer posted one time that he blew over 10 pistons and never scored a cyclinder wall yet.

    Also did you get that ICCU hooked up?And were you playing with it? I have a feeling that your maf is shot or your O2's are gone and you were getting false readings..

    One thing that you can do is its a pain but cheap and you might find the problem if its a piston is take a long skinny screw driver and with the piston all the way at down stroke put the screw driver in the plug hole and follow gently on the top of the piston along the cylinder wall to see if you blew the top of a piston. I have seen numberious times cars run without even knowing they blew the top off a piston. I shouldn't say top but a chip.

    I bet that if you look into it some your piston will look like this
     
    R

    rob

    TCG Elite Member
    Dec 28, 2008
    1,237
    0
  • #21
    Had a brain fart ladies and gentelmen..... :blink: Was thinking of changing BEARINGS from the bottom end in the car......not a PISTON........sorry.

    Was thinking that if you had good compression/leak down and no indication of fragment damage or on the electrode of the plug to identify the faulty cylinder/piston that a scope may be warrented.......Given this is a cracked piston protocol...

    If I was unsure wether I chunked a piston.......and still had a cat in place......I would drop the DP and check the input for piston fragments....... However,most of my failed piston wound up inbeaded in other pistons and one seat......
     
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