I have a 99 F-150 5.4L. I hear a knock in the engine when I start heading out on the road and it only happens when I crank it up an hour or two later after driving. It never does this when I crank it cold like in the morning. I baby it for about a half mile and the knock goes away. I read something in the forum about a special oil filter used in the Triton but am uncertain if this may be what is causing the problem. I don't have the Motorcraft filter in it right now and since I bought this truck a few months ago, I couldn't say if this started happening since the last oil change. I had already changed the filter prior to reading that thread and put a Pure One filter in it. It did have a Carquest filter prior to the Pure One. The knock was there with the Carquest filter too. I bought a Motorcraft filter a few days ago and am going to put it in soon. There was also a thread on blown plugs but it seems that a blown plug would cause a constant knock which mine doesn't. Not sure what to do here. Any help would be appreciated.

 

My 5.4 knocks on cool mornings after sitting all night.

My knock made me think that the oil pump had lost it's prime, because the knock would go away after a few seconds.

To reduce my knock, i use motorcraft filters exclusively and motorcraft 5-20 or mobile one 5-30 oil. I also use 6 quarts of oil for each oil change. I now have 94,000 trouble free miles, so the knock does not seem to interfere with the engine.

there is also a thread on PISTON SLAP. This may be what you are hearing. you may want to review that thread to see if it is similar to what you are encountering.

 

What is the mileage on your truck??

Don't know if this is the case but......I was listening to Bobby Likis car clinic the other week...Somebody called in and mentioned something similiar (maybe??)...But Bobby Likis mentioned that Ford Modulars after several miles have a tendancy to coke up the ring packs....Don't know if this is your case or not...But it seemed to make sense when he mentioned it.....

One solution that might help or not (??)....But is a harmless process and I am currently useing on my sons Dakota is a product called Auto-RX....It is basically an oil additive that cleans out the interior of your engine Top and Bottom....It is completely harmless as I have done alot of reasearch on this before I started.....It is not one of these run it for 5min and dump it rip-offs...It works over several thousand miles of driveing.....and not a bad preventive maintenance procedure regardless...

I don't sell it or anything like that.....I am sure it has been mentioned on this site before.... Just an idea for you to research on your own....You can find out all you need to know on a site called Bobistheoilguy...in the additives section...(check out the case study Dennis, a sticky at the top with pics...great success)..or AutoRx has there own site.......