Ok now my random misfire issue on my 2004 x type 3.0 auto is telling me I'm having misfire in cylinder 1(PO 301), cylinder 4 (PO 304), cylinder 5 (PO 305). I recently changed plugs( Bosch Platinum) upper & lower manifold gaskets, throttle body gaskets, new maf, new fuel filter and ran great for a week after changing them and now its starting to have a random miss while driving only. HOWEVER it don't start missing until driving for about 15 minutes seems like it needs to get engine warmed up before it starts missing.Don't miss set idling it has perfect idle, no loss of power, and no indicator lights on. I did find out the detailer did power wash the engine but it ran fine after getting it back from them. What is going on and how do I fix it. Thx for your help.

 

Rainbowboy,

Try taking the manifold off and reseating. Sounds like the manifold gets hot and expands allow for air to be sucked in.

Just an idea. I had a Mustang 5.0 that had a would do the same thing. found the front intake manifold gasket to be faulty.

Let us know what you find.