f150 forums letting me down

[Dead Ranger]

i know this doesnt belong here, but you guys have always been good to me.

my 87 f150 straight six is missing on #6. i swapped injectors, wires, plugs, as far as i can tell, compression is good. it shows the same as the others while it is running. it starts fine when cold but then starts missing after warmup. i cant find any problems with egr or iac, but even so, why only #6? its probably valve or ring but why only after warmup and i want to try everything before i pull the head.

thanks for any ideas

bill

 

[Big Jim M]

When cold the mixture is rich enough and the timing is retarded enough for the fire to be contained near the cylinder.. Then when warm the mixture is leaned out and the timing is advanced so the fire is started and travels into the intake manifold.. By doing this it burns fuel destined for other cylinders.. This makes the miss more noticeable.
Do the compression test again..PROPERLY.. this time and get back here with the numbers. If you havn't swapped out the dist cap I'm betting on a burnt intake valve on #6.
Big JIm

 

[Dead Ranger]

I havent swapped the dist cap ill get proper comp numbers in the morning, its cold dark and damp right now ...thanks so much for replying...i tend to think valve too, no smoke so prolly no ring. i gotta get a ranger

 

[Big Jim M]

Do the cap first..
Big JIm