I have a 2005 f-150 5.4L 8 cylinder truck. The engine started vibrating recently. I don't know if it is the alternator, spark plugs, COPs, or whatever. My first guess was the alternator because I can feel the engine and driver's wheel shake a little. It feels like it has weak torque. I tried revving up the engine while driving to see if it would help, but the warning light started blinking instead. Later on, I test drove it again. The engine light is staying on, but after driving for about 10-15 minutes the engine light started blinking again.

But after reading some posts, it sounds like it might be the COPs and spark plugs. Any help would be greatly appreciated. I don't have a diagnostic tool right now so help is needed here badly. Thanks in advance.

 

What codes is it throwing? What is the mileage? Have the plugs been replaced?

 

I don't have a diagnostic tool to read codes right now. I live in a remote village that doesn't have connecting roads to a city nor do we have any auto mechanical shops that I can bring my truck to. I changed my spark plugs and coils about three years ago and it had 79K miles, and there is about 91,000 miles. I kind've don't think it is my alternator and believe it is the spark plugs. But what would be causing my truck to shake???