I have been struggling with misfire and lean/rich conditions.
My questions: Should I now change the o2 sensors? If so can I change one of them and see if the rich/Lean codes go away so I can see if that's the problem or not.. just so I don't spend an extra $60 if the o2 sensors arent the problem. If so which one do I change or does it matter.

Symptoms: Codes p0175 0172 (rich file a few weeks, now lean) p0304 (misfire #4) p0316 (misfire first 1000rpm)
acceleration struggle, cuts off randomly, turns over quite a few times before it starts.

So about a month ago my truck went from "skipping a beat"/a little trouble... to barley drivable. I Changed MAF. I did a homemade smoke test then Changed a couple of vacuum hoses.... no help.
Then changed #4 spark plug. TRUCK WAS RUNNING PERFECT for 150 miles. Now all of a sudden it's starting again. So I read codes and now have p0304 (rich) instead of p0304 (lean) also those codes popped up a few miles before the misfire code.... So..... o2 sensor... right? If so why did spark plug fix problem for 150 miles? Because now I still having misfire.

 

Leave the Ox sensors alone. They are not the problem.
The OX sensors are the only way the system has to detect and report an issue with the induction system up top.
They are at the end of the line so they cannot be the cause of 'your' codes.
Fix the 304 cylinder 4 first, then see what you have . The 316 will clean when the 304 is gone.
It may be coolant leaking from a heater hose connection right above it.
If still 171/174 then you have a vacuum leak. That would be two troubles at the same time causing confusion.
Believe the codes and not your thoughts.
Good luck.

 

So check the hose for leaking coolant then what? I've looked everywhere for that vaccum leak. I'm ready to put on a face shield and spray starting fluid on it to find the leak.
should I start with changing the rest of the spark plugs or wires? Sounds redundant because there are lean codes... that's what's causing misfire... NoT the other way around. .. correct?

 

I hear your frustrated about not being able to get the repairs.
On a 2003 you have coil over plug ignition (COP), not plug wires.
Trust the codes set because they are telling of the issues present.
Re do the cylinder 4 coil and plug installation to be sure the plug does not have cracked or broken porcelain, the boot is in good shape with no pin holes or hardened cracks, that boot sets down on the plug and not jammed off to the side.
Be sure the coil connector is firmly on and locks in place.
You could swap the coil with another cylinder to be sure its not the coil or the misfire goes with the coil.
.
How a misfire is detected: the front crank sensor measures the rotation time of every cylinder every time. If the time is slower than the average of all other cylinders and is slower for a certain number of times, the cylinder is called a misfire and sets a code and dash light. Any cylinder fault can cause a misfire from a head gasket to a leaking valve or injector. Its basically a loss of cylinder pressure to rotate the crank shaft at within minimum time limits.
Do not go into changing any other cylinders parts but what is set for codes.
.
You need to solve this code first so you can tell what and if there are other issues. Some issues can have 'inter related' causes such that the first detection is the only one you have to work with.
Then address any others on an individual basis.
Do not labor over what ifs, what abouts etc. only what the codes set refer to or you keep yourself suspended in thoughts and not focused on the causes of an issue.
Codes never tell you specifically what to replace but what part of the system is in trouble.
Good luck.

 

Thanks a lot. That makes sense. Very detailed! appreciate you taking so much time to help me. I will go and try that today.

 

wait are you sure?? Maybe I'm confused about something but the spark plugs go in the engine and a wire directly on top of spark plug... then all those wires go to a gray box... aren't the coils in there?
But event if it is not a COP your theory still stands correct. Still Change coils around and what else do I check?

 

I see you have posted this same issue in the Ranger forum and previously here in this one.

I have no idea what vehicle you are working on and I don't want to sort through your old posts to try and find out. In order for me or anyone else to try and help you we will need to know exactly which vehicle you are working on and which engine it has, neither of which you have provided in this thread.
If you would keep the same issue all on the same thread it would be easier to follow and help you solve your problems.

A 2003 F150 V6 was originally equipped with one coil pack mounted on the right valve cover. Both the V8s offered in 2003 in US F150s had coil on plugs (COP) which are individual coils mounted on top of each spark plug hole.

If you have a V6 and you have already changed the spark plug #4 which is showing the misfire code, then my best guess is that the #4 spark plug wire is shorting out and needs to be replaced. Some parts stores sell singles or will break up a set.
At this stage of the game though, it really sounds like you need to change all the spark plugs and all the spark plug wires, if you indeed have a 2003 F150 V6.

 

Yes I have a 2003 v6 f150. Sorry about the confusion I've never owned a ranger. I did accidentally posted on someonelse thread that keeps popping up when I first log in.
And ok sounds good I'll change all plug soon and wires now. Should have done that to begin with.

 

I changed all wires and plugs with platinum motocraft and premium wires. It's running better. No misfire that I can tell. It does come close to cutting off at low rpms a few times... It needs to be inspected within 10 days. Hopefully I can figure out the rich codes. They haven't come back yet but I suspect they will. Could I possibly get it inspected after 40 miles and if the codes haven't come back yet

 

Thank you again for your time. Hopefully with your help someone else also.

 

The rich code may have been from misfiring, pushing through too much unburnt fuel.

Don't worry about codes you don't have now.
Clear old codes before you drive it too far. Unhook the battey for a half hour then hook it back up and drive it normally. Then see if any codes pop up and go from there.
At that point, IF there are any more codes, start anew with a clean sheet of paper and troubleshoot to fix only THOSE codes.

 

Just for clarification, the O2 sensor doesn't sense unburnt fuel. It senses the presence (or lack) of oxygen. So a rich code would result from lack of oxygen in the exhaust.