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2004freestarmatt -> RE: 4.2l ping between 3600 & 4200 rpm (11/27/2007 5:40:25 AM)
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I had a similar sound with my 2004 freestar when I first got it and I also had it with an earlier 4.0L in a ranger. This problem is just carbon build up in the combustion chamber. If this is your wife's van, she probably doesn't run it very hard, ie above 3500 rpm. This aids in the production of carbon. The fix for my van was to take it on the highway and run it in 3rd gear and accelerate hard, ie on the floor, and then let off and accelerate hard again, do this about 6-10 times and you should hear the noise get less. You need to heat up the combustion chamber to burn off the deposited carbon. The higher the revs the better and the more load you can put on the engine the better, ie up a hill. After doing this with my Freestar, the pinking noise is completely gone under all loads and rpms. The exact same thing worked for my old 4.0 L engine. Worth a try... [8D]
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