Valve Spark?

Dead_BunnyDead_Bunny Wagonist
in Engine & Drivetrain
Over the past a few months I’ve noticed a “rattle” sound from under the hood and I couldn’t figure out where it was coming from. I knew it was coming from the engine bay, but nothing was loose and I heard nothing when revving the motor while in neutral. The rattling sound could only be heard while the motor was under load, usually from 1-3500rpm, and or accelerating. So finally I took it by my local mechanic, as soon as he heard it he knew what it was. He said it was “valve spark” it’s caused from cheap gas (with high ethanol content or high water content). So I threw in some fuel system treatment to see if that helps out and or clears it up. He also suggested that I use ethanol free gas, or steer clear of Kroger, and cheap gas stations…they usually have bad or worse gas.

My question is; does this seem legitimate to you? Or do you think this could be a different issue completely?


...i'll update this if the fuel treatment and ethanol free gas works...

Comments

  • rti intracrti intrac Senior Wagonist
    Could the mechanice be meaning detonanion? If it is detonation you could try running premium/higher octane fuel ore try retard the timing a couple of degrees?
  • ragenasianragenasian Moderator
    Did he mean Spark Knock??? I had that problem as well and mine was caused by a leak in the intake manifold gasket (on a different car).

    Here is a link about it and it sounds like the problem you are talking about.

    http://www.dnd-automotive.com/tuneup/spark-knock.htm
  • danzdanz Wagonist
    ethanol blended 87 (r+m)/2 fuel will not suffer detonation or knock any easier than non blended 87 (r+m)/2 fuel



    how ever u may have large deposits in the combustion chambers that are getting hot spots and causing pre-ignition, but its very unlikely




    try filling up with 92 octane, or what ever the highest octane fuel you can find is. if it still makes that noise, then your problem is NOT knock.




    i run 11:1 compression ratio on 91 octane with zero knock issues at all.
  • Dead_BunnyDead_Bunny Wagonist
    Well the fuel treatment kit did very little, since then I filled up with premium and virtually all of the “tink” or “knocking” sounds have been eliminated (unless under full throttle in 4th or 5th). At this point I’m pretty happy, but I’ll let you know how premium non ethanol works.
  • danzdanz Wagonist
    if anything the ethanol blended fuels will be less likely to suffer detonation or pre-ignition because the alcohol in the fuel removes more heat from the combustion chamber than gasoline would.



    try filling up at a different gas station maybe the one you go to got a bad batch of gas.

    also make sure your distributor/timing is set correctly.

    you shouldnt get any knock at all with a stock engine.
  • crxedcrxed Band Wagon
    danz wrote:
    also make sure your distributor/timing is set correctly.
    you shouldnt get any knock at all with a stock engine.

    I was just gonna say this: Have you even checked your timing?
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