This past summer my F250 developed a intermittent miss while at idle in gear - but only in the high altitudes of Colorado.

Got back to Texas as the miss disappears.

Go back to Colorado last week (towing travel trailer again) and the miss returns.

Get back to Texas last night and the miss at idle is gone.

Also I noticed that when pulling long grades and the engine vacuum drops to near zero (I installed a dash mounted gauge) that there will be a miss - but it won't do it constantly, you can feel a slight jolt in the seat every so often of a dead miss.

Any ideas? Thanks in advance, Paul.

Oh - it's got 95,000 on the clock.

 

Maybe it's time for a tuneup with new air filter etc. Don't know connection with altitude thou.