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Originally Posted by rdwoodwright
dealer took 3 times to diagnosea misfire on #5. 1st was a plug change. 2nd was what they called a "carbon soak".Which they claim should be performed every 30k on all models....go figure?doesn't say that in the manual. After 2 weeks the light was back on so back to the stealership she went. 3rd attempt they opened it up and found a bent rod and mushroomed head. They claim as a result of the carbon the head wasn't rotating which caused it to overheat and caused the rod to bend and head to mushroom...not sure I'm buying that? They think the vehicle must have been driven only in the city and never was blown out on the highway...go figure. Did I mention I'm no longer trusting them and I'm hoping we're not the ones who actually get "soaked"!
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Somehow I missed the above post...
Anyway, the first lesson learned is - STAY AWAY FROM DEALERSHIPS!
Sorry, but the incompetent and disreputable way they operate really steams my clam.
No way it should take three tries to diagnose a misfire.
1. Carbon soak.
First off, I've never heard that terminology before but...they have no way of determining the amount of carbon build up INSIDE the motor, or even suspect it at 50k.
2. The "A Carbon soak should be performed every 30k on all models" statement is pure BS. Some people choose to do it on high mileage engines, sometimes the valves may get too carboned up to rotate, but not often.
There is no routine maintenance that calls for decarbonization at ANY mileage, much less 50k.
There are decarbonizers that can be added to the fuel tank -- every 5 or 10k miles--as a preventive.
3. Quote: "They claim as a result of the carbon the head wasn't rotating which caused it to overheat and caused the rod to bend and head to mushroom..."
That's nonsensical, heads don't rotate. Maybe the reference was to the valves not rotating, but that's a performance problem, not a destructive one.
4. Some decarbonizing methods call for the product to be introduced into the motor via the manifold or throttle body. This essentially floods the motor and causes it to stop or at least stutter. The decarbonizing product is a liquid and not compressible, so if it was done improperly it could have caused a hydrostatic lock, and the result is just as you described - a bent rod. The "mushroomed head" is a new one for me, they probably meant a warped head...if it even happened.
It could have had a warped head to begin with.
There are a number of possible scenarios that could have caused the motor problems you had, but I would just chalk it up to experience for now.
My advise is to stay as far away from the dealership as possible, and find a reputable independent mechanic - now before you need one.