Last night I was on my way home. The truck was running great. It suddenly starts acting like it is misfiring. I was waiting for the "Check engine" light to come on. It did not. A few miles down the road the motor started making this awful hammering noise. I pulled off the road and shut it off. The hammering noise sounds like it is coming from within the motor around #6,7 or 8 cylinder. Have I broke something serious? My ole truck is a 2000 5.4L Lariat with 166,000 miles. I change the oil regularly and do not drive it hard. Any thoughts?

DaWG

 

It might be a blown plug.

 

Would check that area for a blown plug. Have you had plugs replaced recently?

 

No blown plugs. The mechanic states he climbed under the truck with it running. It is deep within the motor. He fears we spun a bearing or broke a wrist pin. New 5.4 on order. $5100 installed, with a 3-year unlimited mileage warranty.