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HELP!!! long but much needed and appreciated

Discussion in 'The Lounge' started by Itali83, Mar 4, 2003.

  1. Itali83

    Itali83 1/2 ton status

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    Ok here it goes... I own an 86 oldsmobile cutlass supreme with the 307 v-8 and 4bbl 4EMC carb on it and an auto. I drove the car from maine to nashville where i"m going to school. The car has a habbit of pinging when under a load and it's driving me nuts + it's not good for the motor. This is the list of what I've done to it to try and rectify the pinging.
    TPS was bad so that has been replaced.
    O2 sensor was dead so I replaced that
    MAP sensor was iffy so I changed that
    Full tune up including, rotor,cap, wires, plugs.
    Timing was set at factory spec and double checked many times.
    These are the things I've checked to make sure are working.
    EGR. It is operating properly and I can feel it open with my fingers. EGR passages are also not blocked because if I open the valve at idle, it will kill motor.
    I've put a snap on scan tool on it many times and there are no codes present, and all of the sensors look in check and nothing out of order. Temp sensor is reading correctly as well as the new TPS, MAP, and others.
    I put a dwell meter on the mixture control soleniod, and when in closed loop, it's varying between 30-40 degrees which is text book perfect, if I hit the gas quick, it goes down to 6 degrees, followed by almost 56 degrees and then back to 30-40 degrees.
    As for the pinging here are the symptons... driving around anywhere in 2nd gear or higher, and hill I come to it'll start pinging, or clacking I should say, but it's only at a certain throttle position, if I put my foot more into it it'll go away. If I put it in drive and power brake it without spinning the tires, it'll clack. I had my friend stick his head under the hood and it sounded like the clack was only coming from the drivers side bank, or it was definitly louder on that side.
    The only thing I'm thinking it can be is the computer is not taking control of timing (does not have vacuum advance). But if the computer is leaving the timing at the base (20degrees BTDC) I would think that it would run like a total piece of junk and probably clack a lot more than it does.
    I run regular gas in it, but I've also run two tanks of super with two bottles of 104+ octane boost with no change in clacking.
    I've pulled the plugs and they are white with no black oil or carbon on it. Clean burning plugs if you ask me.
    I'm totally stumped on what the F@ck is wrong with the car. I don't feel like burning any pistons up and I need this car for another 6 months and a 1300 mile road trip back to maine. I really want to have it stop pinging/clacking. If anyone has any ideas or ways to test stuff, or personal experiences or anything please help me out. Thank you very very much for reading it all and for the info. Thanks
    Ben 87 Jimmy + 89 Blazer
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  2. ZonkRat

    ZonkRat 1/2 ton status

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    I can be wrong,but,I don't think the computer controls the timing on 86.Try retarding the timing a little to see if it helps.Did it do this while in Maine?Could be you were closer to sea level there and different atmospheric pressure is causing it to run lean gas mixture down in Tn.My wifes 85 olds does similar with any gas but prem in it.These engines burn lean anyway and it doesn't take much to cause spark knock{preignition}. /forums/images/graemlins/thumb.gif
     
  3. Itali83

    Itali83 1/2 ton status

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    It definitly is computer controlled timing, there is no vacuum advance on there, but a 4 wire connector. I backed the timing off to just above the point of running like a total dog and falling all on it's face and it still clacks like a mother. I'm going to try and get my hands on a timing light and see if the computer is taking control of timing but I really don't think/hope thats the problem. Thanks
    Ben 87 Jimmy + 89 Blazer
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  4. newyorkin

    newyorkin 1 ton status

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    I had the same car, same motor. It would do the same thing, ping under load. The motor blew in that car late one night as I approached a hill with it. It was the second 307 for that car, too. I think that was the first car I swapped a motor on, too...
     
  5. ZonkRat

    ZonkRat 1/2 ton status

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    Could it be carbon buildup on pistons raising compression?Wild guess.My wifes car has been doing same way for several years now.She never hears it,but,I still do in hot weather.It's not as bad during winter.You might try setting to a fast idle speed and pouring small trickle of Marvel Mystery Oil into carb,this is supposed to break up any carbon buildup on the pistons.Old trick,but,it helps hers in summertime.I've seen people do this with water,but,I trust M M Oil more.If nothing else it lubricates the valves a little. /forums/images/graemlins/thumb.gif
     
  6. EDdaTREE

    EDdaTREE 1/2 ton status

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    There's some stuff called "GM Top Engine Cleaner" available from dealerships...supposed to really kick butt on the carbon and valves. Same kind of "pour it in the carb" usage. Also sounds like rocker-arm issues on the left bank? Olds was REALLY known for that one!! HTH!
     
  7. Itali83

    Itali83 1/2 ton status

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    Ok new update... Bye the way, I've already used the GM top engine cleaner and it made no difference but it sure did clean the motor out, so I doubt there is any major carbon build up in the combustion chamber.

    I just got the chart and checked both my baro sensor and vacuum sensor, both are in spec so now I'm leaning towards the computer being the culprit. I know the last two owners and I'm going to call them and see if they every had the computer out and why ( in know they did at some point becuase the clips are broken on the computer cover) and I'll go from there. I picked my teacher's brain (worked at an olds dealership all his life) and he said if the vacuum and baro sensors checked out ok, then it's probably the computer so I'm going to report bakc to him with my new info I found today. Thanks and keep it coming guys!!
    Ben 87 Jimmy + 89 Blazer
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  8. Itali83

    Itali83 1/2 ton status

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    BTTT ???? Thanks
    Ben 87 Jimmy + 89 Blazer
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