My truck is running rich on banks one and two and its idles rough when stopped at lights and such I cannot find the fuel injector pressure regulator under the hood I'm at a loss I have a 98 ranger 4.0 Both two wheel and four wheel

 

a. Are you using a live data scanner to see the rich trims? Is it always rich, idle and cruise and snap throttle?
b. Sounds a little like a stuck egr which you may be able to test by unplugging it and see if the rough idle goes away

 

I pulled the air filter out and saw it was all clogged with oil and carbon I replaced it and it seemed to clear up the issue but I'll try the egr and see if that helps thank you very much

 

 

I'm not sure how to locate it

 

 

Its a k and n

 

 

 

I had troubles with actual motor oil on my K&N filter on my 4.0 SOHC. It was coming from the valve cover ventilation tube attached to my air intake hose. I changed my PCV, and it seemed to help.

I cleaned out the intake tube and washed my filter out with the K&N recharging kit (cleaner and filter oil), and I thought it would be fine.

I oiled too much and the excess was traveling to the MAF sensor. Lesson learned.

Go lightly. Very lightly

I've also been reading that the K&N filters aren't good for vehicles with MAF sensors because of the filter oil they use to catch more of the dirt and particulates. Older carb'd engines eat that stuff up no problem, but those MAFs are sensitive.

Out of the box, my K&N was fine with my system. It's when I cleaned it and re-oiled it...

 

Where is the pvc valve located on the 4.0 I cant find it

 

I've used K&N for over 20yrs on MANY different cars. Only once did I have a MAF problem. And that 1 time was a piece of debris on one of the wires.
All it takes is a little MAF spray cleaner on the MAF wires about twice a yr. It's a way overblown concern.
Also, I rebuild / modify engines. And on the engines that used K&N for yrs prior to being rebuilt the wear looks perfectly normal as compared to ones that used paper filters.
IMO the carbon from EGR contributes 1000% more to buildup in the intake, valves, and bore scuffing.

 

 

I replaced the air filter on my 98 and that cleared up the bank 2 running Rich now it still reads bank one running rich it's not the egr or the pcv valve I'm at a loss of where to go from here

 

 

My next step is to clean the maf sensor that seems to be the only other solution

 

 

On a V6 or V8 engine one bank running lean or rich can be an upstream O2 sensor issue on that bank
O2 sensors use a chemical reaction like the battery does, so they do use up the chemicals and start to fail, 100k to 150k miles is recommended change period

BUT............if there was an engine problem that caused oil or coolant to go into the exhaust then that can shorten the O2s life

Air filter, MAF sensor, temp sensor, air temp sensor, PCV Valve, upper intake manifold vacuum leak, all effect BOTH banks
Lower intake vacuum leak, injector issue, leaking valve stem seal, would just effect one bank