Possibly detonation...help

Discussion in '1994 - 1995 Specific Tech' started by Ryleighsdad, Feb 4, 2013.

  1. Ok guys. Once again I am back with another problem. My car is making a sound that I can only describe as "a non-rhythmic rattling" under acceleration. The sound is a bunch of sharp pops almost like there are marbles in the engine or something is hitting something else. The harder I push it, the worse it gets.

    It is only doing this under acceleration and not sitting still. It does it worse in high gear at low speed and I go anywhere past 1/2 throttle. It is also worse when I run low octane fuel. Running 93 octane helps tremendously but does not alleviate the problem. It only does it when the engine is under load. I can slowly run all the way to redline without this noise occuring, and I cant reproduce the sound sitting still.

    I was told by a member here that my car should run fine on 87 octane and I agree. Its a 95 GT 5.0 with stock internals. BBK intake and magnaflow catback. Nearly stock.

    Any ideas?
  2. that's classic pinging lol. you described it like the textbook. bump your timing back (retard it) and try again
  3. Forgot to mention that my timing is at 10* with the spout out. Why would this thing ping being mostly stock and running stock timing and still do it using 93 octane fuel?
  4. Has this been happening for a long time, or just on one tank of gas? Possibly you got a bad tank of fuel.

  5. Multiple tanks from multiple stations.

    Temp gauge always reads between the R and M on the gauge. Is this proper operating temp?
  6. is it possible the timing mark is off? maybe the distributor got spun or not tightened down.. I would take #1 plug out, make sure its at tdc and verify the timing mark.
    BradleyMustang3 and ratio411 like this.
  7. You probably have either excess carbon buildup in the engine, or you are running too hot of a spark plug.
    (You could also be running lean... but that is less likely.)

    If you are sure the timing is set at 10* with the spout out, I would proceed to lowering the heat range of the spark plugs, and pretty fast.
    The pinging you describe can damage your engine in a millisecond.
    Carbon in the cylinders is a sure way to get detonation, but much harder to remedy.

    I hope it's just bad gas though. That would be your optimum situation.
    Get gas from another source for a while. There is no reason your car should need more than 87 octane, especially when you say 93 still pings.
  8. Check the computer for codes. A bad ERG can cause mid throttle pinging. It will throw a code, but not a check engine light.

  9. Carbon can be worked out with Seafoam. Buy a can at your local auto parts store. I pour about 1/2 can into a wide-necked container, then while the engine is running I disconnect the vacuum hose from the fuel pressure regulator and put the hose in the container. Engine vacuum will suck up the Seafoam fairly quickly. If the engine stalls while you're doing this, just start it back up and keep going. Once the Seafoam is gone from the container, shut the engine off and let it sit for a half-hour to an hour. Then take it for a drive. If you had carbon buildup in the cylinders, you'll get a nice James Bond-like smokescreen for a little while. That's the carbon buildup burning off.

    Seafoam will not hurt your engine if you use it this way, but it can reveal problems. For example, really bad carbon buildup can wear down the piston rings. Once you remove the carbon, the piston rings don't seal correctly and you start burning oil. This is a fairly rare situation, I've never heard of anyone actually having any issues using Seafoam.
  10. I have used it, and even did many treatments to customer cars when I was in the automotive business, but I have also seen it wash out/unseat piston rings, so you have to be careful with it. Personally I think it is overrated. I have never seen any proof that it actually does much for heavy deposits. ATF into the intake does the same thing. ATF is just lightweight oil chock full of heat activated detergents. The old guys used ATF before Seafoam.
  11. Ok...Thanks for all the responses guys.

    Modulistic - I recently replaced the distributor and I have triple checked the installation to make sure I did it correctly. I have NOT taken the plugs out and verified TDC yet.

    Ratio - I have already run 2 cans of seafoam through the engine from the brake booster vacuum line, and got only minimal smoking. The plugs are the Motorcraft plugs recommended by the Haynes manual gapped to factory specs. Also I have been bouncing around getting gas from a different station every fill up. Same problem with any mid grade from any station. I filled up on 93 yesterday and the problem is all but gone today. Every now and then I can hear a faint click, but not the marbles like before. BUT this car should run on 87 with no detonation...

    Revhead - I will check for codes ASAP. What is an ERG? Ive been around cars all my life and have never heard that acronym. lol Did you mean EGR?

    I did notice that the harmonic balancer has a wobble. It has about 1/8" inch or so of movement while running. The movement appears as though the HB is not on straight(like a crossthreaded bolt). I dont mean it wiggles left and right or in and out of the engine...just a wobble. I read somewhere that these engines can spin the HB fairly easily. I assume the TDC check would prove if this is the case?
  12. that's a really weird symptom man. I would replace the balancer just by seeing that.
  13. Looks like I might be doing that first then verifying TDC and timing are correct.
  14. Any movement in the HB is bad news and invites a lot of internal damage. That wobble most certainly means the HB has slipped rendering any timing assumption useless.
  15. Unfortunately spun balancers seem common on the SNs.
    The parts are the same as any other Ford, so I wonder if it has to do with the relocated accessory drive on the SN?
    (That is just thinking out loud... not wanting to get into that discussion.)

    If your balancer spun before the last time you changed the timing, you could have it too far advanced.
    Actually that makes the most sense to me, as you are correct... the engine SHOULD run on 87 just fine.
  16. Next stop change the balancer and re-time. I have a laundry list of stuff that this car needs...

    steering is loose
    cable for top is not attached on pass side
    pass side 1/4 window is off track
    aftermarket headlights aren't aimed correctly
    brakes need replacement
    smog system needs removed

    lol, It never ends.
    ratio411 likes this.
  17. in the meantime, you should experiment with moving the timing back until it quits knocking, to avoid major engine damage.
  18. I will do that tomorrow...Thanks guys!
  19. Ok so I replaced the balancer and verified the timing is set at 10* as far as the balancer is concerned. Problem still persists. I am going to try and verify timing with the engine at TDC tomorrow, but no promises.

    From my understanding the only way it can be off yet the balancer still read correctly is if it jumped a tooth on the timing chain right? What are the odds of that happening?
  20. Are you seeing blue smoke out of the tailpipes under load or any other indications of buring oil? If your PCV valve is stuck open or you're buring oil by some other means (stem seals), oil in the combustion chamber will reduce the knock threshold of your engine.

    Replacing the balancer was a good call since there are a lot of posts here about the timing ring spinning with age. I don't want to offend you here, but are you sure you're timing it off of the correct pointer mark?

    If you do have it timed correctly, another possibility could be the shear key for aligning the damper. If the key is partially sheared, the crank alignment to the damper could be off. I think this is a pretty rare failure mode but still a possiblity. Were you able to get a good look at the key when replaced the damper.

    Good luck! I hope it's something simple, easy, and cheap.