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    lgoldman New Member

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    Hi,
    I have a 2004 Prius and it had been shaking a bit around 25/35 MPH after driving for about 1-2 miles recently. The shaking was similar to what it feels like when a car is about to stall. This happened for a few weeks mildly and then got worse over the weekend and the check engine light went on. I took it to the dealer today and they reported back that there is water damage to the ignition coil. I find this strange because I live in the SF Bay Area and we are in a drought - thus very little rain or car washing.

    Any ideas?

    Thanks!
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    jdenenberg EE Professor

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    There was a TSB on this problem:

    EG063-05.pdf

    JeffD
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    richard schumacher shortbus driver

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    Has the drive (engine) compartment ever been washed?
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    morpheusx Professor Chaos

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    occasionally ignition coils can go bad for a variety of reasons.
    The ignition coil plugs directly on top of the spark plugs and basically converts low voltage into high voltage and feeds it directly into the spark plug to ignite the gasoline/air mixture in each cylinder. They are insulated with a rubber sleeve to keep out moisture (usually from the natural humidity in the air). As they age it is not uncommon for the rubber to get a bit of wear from excess heat. Usually the tell tale sign will be cold start problems and a rough idle. It is one of the most common failures of the modern engine. The good news is that an ignition coil can be replaced fairly cheaply and does not require you to replace all 4.
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    lgoldman New Member

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    No the drive compartment has never been washed
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    lgoldman New Member

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    Thanks for this info, that helps. Although I wonder if this expected with a four-year-old car. Also, about three years ago, I also had water damage on a spark plug. I read the TSB referenced above, and I wonder if I am not fixing the root of the problem - ie the water leaking from outside. Any thoughts?
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    morpheusx Professor Chaos

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    just brainstorming a bit, would it be possible that your windshield washer fluid hose has a leak and sprays under the hood when you need a squirt or two to clean the windshield.
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    Patrick Wong DIY Enthusiast

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    The last page of the referenced TSB suggests that you pour water over the center seam of the cowl cover. See if water leaks down to the engine. If so, then the center seam needs to be caulked so that the engine will stay dry.

    Three years ago when you had spark plug damage, your tech should have caulked the center seam to avoid a recurrence of the problem.

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