Hello everybody,
I’m brand new to the forum. Looking for some tips or advice on my truck. I have a 2004 Ford Ranger Edge with a 3.0liter V6. My truck throws codes p0305 and p0316 after about 2-3 hours of driving. I know p0305 is misfire on cylinder 5 and p0316 is the first 1000 revolutions. You can Pull over into a parking lot or stop at a drive thru after the long drive etc and you’ll start to notice it start running rough and shaking then the check engine light starts flashing(which throws the codes p0305 and p0316). You Start driving again and the check engine will go to a stay lit check engine lit not flashing then go away. Driving it seems to make the misfire and rough idle ands shaking go away. Letting it sit for a day or two when it’s misfiring with the check engine light on will also make the check engine light go off and misfire go away and run fine. The spark plugs were changed 4000-5000 miles ago. I changed out the ignition coil pack and it still does it. It only does after long drives. Commute around town and the misfire check engine light doesn’t come on , no misfire and runs fine but a few times it’ll start have a rough idle at a stop light but it’ll go away and a check engine light will never come on. Idle rpm is at 600-650. It’ll go up and down from 600 to 500 and does it a lot even when the truck is running fine. It’s getting bad gas mileage as well. Not really bad gas mileage but I’m getting roughly 300 miles a tank? I don’t know if that’s bad. The truck accelerates fine too. Anybody know what might be causing this or has had a similar problem?

 

Welcome to the forum

The 2004-2006 Ranger 3.0l engines had an issue with recessed exhaust valve seats
Ford put out a TSB for it, seen here: https://www.therangerstation.com/for...n-tsb-05-26-3/

You are going to need a compression test to see if this is the problem
And most likely will need to replace both heads to fix the issue


Valve seats are pressed into the heads and when valve closes the seat/valve mating holds compression pressure
Exhaust valves and seats get very hot, I guess Ford installed some "bad seats" in the 3.0l heads, not 100% just a higher percentage
If a valve seat shifts position when it heats up then compression in that cylinder drops below needed compression for that cylinder to fire, so "misfire codes"

P0305 on its own could be bad spark plug or failing injector, but P0316 random misfires, point more to the valve seat issue
Compression test would tell you more

 

But wouldn’t this happen anytime the engine heats up?

 

No, not always
You do a compression test on cold engine to see if any cylinders are lower than the average, if so and that corespondents to your misfire code then its most likely a valve issue

You can change spark plug and injector and if problem still occurs you pull the heads

A gasoline engine misfires because a cylinder is missing one of these
Compression
Spark
Fuel

I always start with compression because its mechanical, black or white, good or bad, no grey area
Then move on to spark and fuel, these are a pain because they can be intermittent issues

How you approach it is up to you