Thumping noise when accelerating


New Member
Mar 12, 2020
Albuquerque NM 87108
Okay my mechanic friends.. The mustang has a knock..
2004 mustang v6 40th anniversary cool air intake but otherwise stock....

Trying to figure out diagnosis.. No metal pinging sounds. It is only when its accelerating, feel it in the pedal. Does not shake wheel or car, it almost sounds like a flat tire with a thump thump thump.... but engine is shaking maybe more then normal, always seemed to move more then the jeep and I cannot tell. Anywho..
Couple things to mention. Just did an oil change on Sunday wife noticed it yesterday(Wednesday). Says its getting worse... Recently have had made repairs on air system. Cant remember part I replaced but it was at the tail pipe end. Last tune up was 5yrs ago replaced spark plugs, 2yrs ago had engine oil gasket, clutch gearbox replaced, as well as head gaskets. Had to take back year later due to air intake issues. This last year had issues with 2nd spark plug on passenger side. (V6) pop out twice (previous mechanic either over tightened or did not secure) had new mechanic fix that. Also 1 yr ago replaced o2 sensors.

Doesn't make noise when idling or accelerating engine at stand still in neutral. Sat there revving engine and can only slightly hear it. So I don't believe its a rod or internal mechanical issue. We drove down the street sounds like its got a flat, but again no noise when sitting in idle or revved.
Any suggestions besides putting this old thing out to pasture??
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