hesistation or miss at idle after tuneup

i had a severe occasional misfire on the interstate so i decided to do a tuneup. plugs, cap, rotor and an o2 sensor. now i get the mis at idle. what gives?

'95 4.0 aw4

Is it throwing any codes? If so what are they

nope, no codes.

Excessive resistance in the plug or coil high voltage wires will do that. It's easy to miss with the spark plug end at the spark plug contact and leave a gap or have the contact at the end of the plug cables slip in the boot and not make good contact at the distributor cap. It's always a good idea to look at the carbon contact in the center of the cap also, ohm check it. I actually had one fall out once.
It's also common to bend old cables the wrong way and break the core. An ohm test usually finds this quick.
I've inadvertently slide many plug wire ends inside the boot when reinstalling and caused an idle miss.
Could be something else, but this is likely the best first place to start looking.

how would i measure the resistance at that carbon contact in the cap?

as far as the wires, i could try a different set i guess.

When you gapped the plugs, could you have bumped one while installing enough to change the gap?

joe_peters said:

When you gapped the plugs, could you have bumped one while installing enough to change the gap?

Click to expand...

i wouldnt think so, im normally very careful but thats something to check.

tigerShark said:

how would i measure the resistance at that carbon contact in the cap?

Click to expand...

nevermind, brain fart.

edit: how many ohms should it read?

the resistance should be zero from the top of the cap to the underneath(might be .something, but less than 1).

A good trick to chase down an idle miss, is to hook up a timing light to very spark plug cable 1-6 and shine the light on something dark, so it stands out well. You may be able to actually see which cylinder is missing this way and avoid going back through the whole job again.
Random misses are usually the coil to cap cable or sometimes a very weak spark for whatever reason.