Fuel Pressure Fluctuation

[Rawze]

(05-31-2020 )B model Wrote:  ...
917k miles on it and it has recently developed a kind of miss when idling.
...

My engine at 985k was loping at idle a bit, especially when cold. My head was worn out. - When i did the inframe, I literally replaced no components in the top end except the head itself. - i re-used all of the million mile parts, rockers, cams, injectors, all the IFSM components,,, everything. - The engine ran smooth as a button with no lope, no misses when cold,.. like a new engine again. - In my case, all the lope, miss, etc. was simply the worn out head (non-lubricated parts like valve seats, guides, etc).

You having 900+k on the head, it could be exactly the same thing. - Personally, i would not worry about it if it runs good, given that many miles on it unless you find worn out injectors or actuators.

-- Next Q. would be -- Did you do the rod and main bearings at 800k? -- if not then in a year or 2 more, if it makes it much past the 1 m,il mark, it will be a ticking time bomb ready to send a piston thru the block with zero warning as a wrist pin lets go because no one did the rod/main bearings when they were due. - just saying.