I am getting codes po0300 and po316 on my o4 ranger it idles rough but seems to drives ok .any Ideas? thanks Mike

 

Welcome to FTE.

Which engine do you have, how many miles on it & where are you on all past & present due scheduled maintenance????

P0300 is a random cyl misfire.
P0316 is a start up misfire with under 1000 revoluions.

The misfire & rough idle could be a number of things, from an acting out IAC, fuel injector, fuel pressure, spark plugs, wires, coilpack, computer calibration dirty MAF sensor & if you have the 3.0L flex fuel engine, some more things.

SO, we need some more info to home in on your problem & maybe be able to make a more focused guess.

Did this problem come about after some event????

 

If yours is the 3.0L engine, then I would initially suspect two things:

1) Camshaft sensor and/or synchronizer problem (see: https://www.ford-trucks.com/forums/2...placement.html)

2) Head/exhaust valve problem (see: TSB 05-26-3)

 

it is the 3.0 v6 with 76k miles on it I put about 12k a year on it and replaced the plugs and fuel filter about 15k ago,the truck started running rougher than usual about a week ago so I added a bottle stp fuel injector cleaner to a half a tank of gas and the next day the light cam on.

 

What Brand plugs did you use?

 

OK, so it's the 3.0L Vulcan & I assume it isn't a flex fuel 3.0, it has 76K & you've replaced the plugs & fuel filter about 15K ago & recently added a can of STP fuel injector cleaner to a half tank of gas.

We still need to establish a basic info & maintenance foundation, to begin a trouble shoot, because at this point we don't know if the problem is fuel, ignition, compression, vacuum, or some combination thereof, so more questions to follow.

Our Rangers have a "waste spark" ignition system that requires at least double platinum replacement spark plugs, of the right design as has been asked & heat range, set to the proper spark gap, so did you use the specified Motorcraft or Autolite replacement plugs & check their gap with a wire gauge before instalation?????

Did you torque them to spec & use dielectric grease on the external plug insulator & inside the plug wire boot, to prevent flashover on those wet days or damp dewy mornings????

Were the plug wires also replaced & if so, did you use the specified plug wires, or at least ones that said they meet Fords specifications????

Have you ever replaced the Air Filter????
If so, was it with the specified paper design, or was it with an oiled foam, or cotton gauze type filter.

Any mods to the air intake system, or to the engine????

Was the fuel injector cleaner added at the containers specified cleaner to fuel volume mix ratio????

Have you looked at the spark plug wires, or done a "wet down test" with a spray bottle of water at night, to see if you can spot any arcing & sparking????

Have you done any testing, like fuel pressure, vacuum, compression, or done a cylinder balance test with a scantool????

If you feel all of the basics are right, have you reviewed the two links Rockledge posted????

 

check for a vacumn leak on the elbow of a rubber hose that connects the intake tubes to the left of the throttle body, mine got a leak in it and i got the same codes. I've read other forum posts about the same problem, it seems to be notorious in the V6 motors

 

Air filter is new,spark plugs are the proper motor craft, I can't seem to find a vacuum leak, anyway I put fresh gas in it, replaced the fuel filter and undid the battery to reset the computer,the engine light has not come back on in 3 days but it does seem to miss and idle a little rough now and then.

 

So, are you sying it's better after the injector cleaner was added to the half tank of gas????

 

It seems about the same except the engine light is not on anymore.

 

Update I have done nothing else to my ranger since I last posted my engine light has stayed off since I reset it,my truck runs rough for about 2-3 minutes at start up but then runs fine the weird thing is my fuel mileage is better then it has ever been I am averaging about 2 miles to the gallon more than I ever have and I have had the truck for years.

 

Kinda sounds like it was dirty injectors, as they can cause a random misfire & adding the STP fuel injector cleaner has cleaned them up some.

Maybe consider trying a 20oz Chevron Techron Concentrate Plus at the pump & filling up with Chevron, Texaco, or Caltex gas to get good mixing.

These fuels already have Techron in them & adding the 20oz additional will raise the treat rate 10X above the pump gas alone & will likely finish the job.

It'll also decarbon the intake valves & tidy up the combustion chamber & may help some more to smooth things out.

Let us know how it goes.

 

I used the 20oz Chevron Techron Concentrate and filled up with Chevron gas you suggested and my truck runs like a dream,Thanks for all the great advice guy's.Mike

 

OK, good feedback on the Techron treatment & to hear you got positive results.

Now that things are nice & clean inside & it's running good, you can keep it tidy inside by continuing to use a Top Tier gasoline like Chevron, Texaco, or Caltex, or maybe some of the other Top Tier brands listed here. Top Tier Gasoline & click on the "retailers" button.

These fuels have a higher detergent level than the govt mandated minimum & they also have a maximum level limit for combustion chamber deposit load.

So these fuels are required to not only keep the fuel injectors & intake valves clean, but also the combustion chamber/piston crowns & head!!!!

 

Ok here I am a a little over a year and 10k more miles with a code po303 and po316 going on about 2 months now,I just put new plug wires in,plugs are not that old but I ,may replace # 3 just to be safe,I did a compression check and have 175-185 psi on all cylinders so I am leaning toward a bad fuel in injector or ignition pack,any thoughts?