So my 2001 Ford ranger 4.0 started idling rough sounded like a misfire.so I replaced all the plugs and ignition coil and still has this issue. I have cleaned the MAF IAC and the EGR valve. Haven’t done anything with the PCV vale yet because it’s against the firewall. Any help or advise would be appreciated.

 

Also there are no codes or Check engine light

 

Dump a can of Seafoam in the gas tank to clean injector tips
Dirty injector tips cause misfires at idle because they drip fuel instead of spraying fuel, so you don't get a good air/fuel mix, but mix is fine at higher RPMs with faster air flow

What did the old spark plug tips tell you?
Any darker or lighter tips?


Coil pack spark plug wiring should look like this
3 4
2 6
1 5

The 5 6 4 side often gets miswired, so double and triple check that, trace each wire from cylinder back to coil pack

Coil pack uses Waste Spark, so spark plugs are fired in PAIRS
1 and 5 are a pair so share the one coil in the 3 coil pack
2 and 6 are another pair
3 and 4 the final pair

Thats why coil pack is wired the way it is

 

Plugs were all Burt and gap was compressed so it needed to be done. Wiring is done like you said and I will have to get seafoam

 

Gap should be 0.054 on the 4.0l

"burt"?
Burnt, what color is that, black?
Thats rich running or oil is getting in
were all 6 the same?

O2 sensors are the ONLY sensors that wear out, they run out of the chemical needed to detect Oxygen
They last 100k miles OR 12 years, which ever comes first
When they start to run out they show "false lean" oxygen levels which causes the computer to run the engine RICH so MPG starts to go down and spark plugs show rich running
No codes for this because only O2s could set a lean or rich code, lol

 

Yeah all of the spark plugs were black

 

Then plan on changing the O2 sensors
One or two black plugs could be leaky injectors or valve stem seals(oil)
All 6 is a system wide issue

So if not the O2 sensors then its the computer, it would be better if its the O2 sensors, lol

 

How many o2 sensors are we talkin like 2 or are there more?

 

On a V6 there are 2 upstream O2s, these are the important ones to change

There is a 3rd O2, if its NOT Dual exhaust, called downstream, its after Cat Converters, it tests if they are working
If dual exhaust then there ate 2 downstream O2s
These tend to last longer than upstream O2s, because Cats burn up most of the Oxygen so O2 does use up chemicals as fast
Up to you really, I would change it/them, but the 2 upstream are the ones that control lean and rich running the most