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My gas engine sounds like a diesel!

My 97 Dodge P/U knocks like heck. It sounds like a diesel. Heavy load, light load, accelerating, constant speed, high test gas, doesn't matter. It's quiet at idle and decel. Engine was overheated a few years ago. I ran some Seafoam through it recently to no avail. It's got about 140K miles. Is there anything I can do? Is there a risk from this?

Comments

  • edited June 2010
    The ignition timing is controlled electronically by the ECM. However, any decent mechanic with a timing light can CHECK the operation of the timing advance program and see if there is a problem with the timing settings. If it IS spark knock and you continue to operate the engine, yes, severe damage (holes punched in pistons) can result...

    The FACTORY service manual will have a troubleshooting guide giving step by step repair procedures..
  • edited June 2010
    I think you are hearing the damage done by overheating the engine. Time to rebuild or replace the engine.
  • edited June 2010
    Oh...I really wanted some GOOD news. But I guess the truth will have to do. Ron-man, I was afraid that was the answer. I know timing is contolled by the computer and doesn't get adjusted. I used to have a timing light...in the 70's!

    There's no chance that this is a timing chain getting ready to go, or that a high performance chip might help is there? I guess if I've damaged a piston, those things won't do much. I guess I'll look at what a used or rebuilt engine will cost me.

    Thanks for your advice.
  • edited June 2010
    Your timing does get adjusted on this engine. Your truck has a traditional distributor, and you still have to set it to a baseline, normally TDC, in order for your electronic curve to function properly. If that checks out okay, and it probably will, the knock probably is from your rotating assembly and a different engine is the solution.
  • edited June 2010
    To answer your question, yes there is a chance that it's a timing chain going...or more probably a guide or sprocket.

    But you have to start with the basics. You need to check the ignition timing and you need to check to see if you can definitely nail down where the knocking seems to be originating. And you need to check the compression. If the valve timing is off due to a bad timing chain or one of its assembly parts, you should see that in the vacuum reading.

    Ultimately, you may discover that the overheating did permanent internal damage and you need a replacement engine. But IMHO you don't yet have enough information to say that.
  • edited June 2010
    Thanks for that advice. I will check compression this weekend and post results. Engine has been running for several years since the overheating, so I don't feel like I have an emergency on my hands......yet.
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