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Have a 2006 Ford Expedition. I had noticed about 6 months ago that every once in a while it would rumble or shake when I was going 45-55 mph and with my foot only lightly on accelerator. Now it happens a lot (not all the time) when I have light pressure on the accelerator and pretty much any speed over 40 mph. Note that if I floor the car or have heavy pressure on the accelerator it runs great!

At first I thought this was a first sign of transmission failing but it doesn't spin and during my last inspection the shop ran diags and there were ZERO errors from the transmission. Again I have had 5 cars have their transmission go out and I can tell almost instantly what is going on. This never "spins" or loses contact. And now that this happens every once in a while past the last gear I think I have ruled it out. What do you think the cause is? (Mechanic takes it for drive and says it runs perfect)

  • Ofttimes when you take your vehicle to a mechanic, it will never do what you are experiencing. Just one of those things! – Pᴀᴜʟsᴛᴇʀ2 Jan 26 '15 at 20:38
  • Does it make enough sound that you could record it with your phone? I've also had good luck taking the mechanic for a ride with me. – Bob Cross Jan 26 '15 at 22:36
  • @BobCross - I could take mechanic for a drive and I am sure it would do what it has been doing - easily reproduced now. It's not a big sound... It is almost like someone who is driving a stick but is really clunky shifting between gears. Like the engine drops for a half second then fine. – blankip Jan 26 '15 at 22:38
  • @blankip, that would be my suggestion then for the next step. It's so much easier for the mechanic to understand if you can make it happen while they watch and listen. – Bob Cross Jan 27 '15 at 0:59
  • @blankip does this rumble/shake happen immediately after you accelerate? Does it happen continually whilst you're accelerating? When does it start and stop? Is the rumble felt through the foot, from the engine sound, or can you feel it through the entire cabin? – dooburt Feb 5 '15 at 12:27
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I've had similar symptoms before on a smaller sedan, a Saturn SL2. Turned out that my motor was mis-firing, and the cause of the misfire was that I had oil in my spark plug wells. The oil was due to a leaking head gasket.

I'd recommend you take a look at your spark plugs and wires - depending on their age, you may even be better off replacing them while you're at it and seeing what that does to your symptoms.

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I would suggest that you check your motor mounts. This sounds like a motor mount issue.

  • Can you add any reference as to why? Or fill out your answer a little better on where to check this, how to check them, any references showing what you are talking about (pics as well). 30 characters is nothing to fill up using these basic steps when answering a question. – Pᴀᴜʟsᴛᴇʀ2 Apr 7 '15 at 20:25

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