ideas missing at idle

[black_demon69]

ok 94 4.0l runs rough at idle no engine light or codes.

also seems to be running just a little rich at idle.

plugs and wires were changed at about 10,000 miles ago with iridium plugs
has k&n filter which was cleaned about 2,000 miles ago
maf was cleaned at the same time the air filter was
coil and iac was changed about 50,000 miles ago

i was thinking o2 sensors, vacuum leaks, or dirty iac.

one other note catalytic converter was hollowed out when trans was rebuilt due to it starting to come apart and no extra money to replace it at the time. i will be replacing it when the extra money is available.

so ideas are welcome please

 

[RonD]

My 4.0l eats most spark plug brands, most notable is misfires at idle.
Motorcraft or autolite seem to last longest.
Make sure spark plug gap is .054.

When idle starts to get more misfires a can of SeaFoam in the gas tank will usually clear that up.
The tips of the injectors get a bit dirty so at idle the fuel drips instead of sprays, this causes an incomplete air/fuel mix and misfires, when there is a misfire no oxygen is burned so it is dumped into the exhaust manifold, O2 sensor only "sees" oxygen, and too much oxygen is Lean, so computer responds by adding more fuel so you get an even richer mix at idle as misfires increase.

 

[black_demon69]

My 4.0l eats most spark plug brands, most notable is misfires at idle.
Motorcraft or autolite seem to last longest.
Make sure spark plug gap is .054.

When idle starts to get more misfires a can of SeaFoam in the gas tank will usually clear that up.
The tips of the injectors get a bit dirty so at idle the fuel drips instead of sprays, this causes an incomplete air/fuel mix and misfires, when there is a misfire no oxygen is burned so it is dumped into the exhaust manifold, O2 sensor only "sees" oxygen, and too much oxygen is Lean, so computer responds by adding more fuel so you get an even richer mix at idle as misfires increase.

has autolites now. put a can of seafoam into gas tank, cleaned throttle plate. pulled 1/2 can of seafoam into intake through a vacuum line and let it sit for an hour, cleaned air filter again and re oiled, and cleaned MAF.

miss is not as bad after all of that.

i will be checking plugs today