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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)

Pᴀᴜʟsᴛᴇʀ2
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blankip
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2 Answers2

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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.

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

DucatiKiller
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Matt
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