Hey yall I am having a misfire issue with my 3.0L. I'll give some background information first. So I have owned this truck for a few months, and it always seemed to run well/reliably. Until a few weeks ago, when I began to experience a problem where in 5th gear, at 2100/2200 rpm, the whole truck would give a massive lurch, just one, as if I let out the clutch and pushed it right back in without any gas pedal. This problem had gradually increased, where it would occur several times in a short trip, and sometimes in 4th. I was suspecting a tranny issue until I read online that people have had the same thing happen with automatics; this tells me that it is the engine. Also, the engine would idle a little rough if i let it sit idling for several minutes.
recent maintenance: i just rebuilt a front wheel bearing/brakes, as well as the rear drums. New air filter on friday. The old one was really clogged up.
Then just this weekend, the truck overheated while I was driving home on the highway. I believe due to a low coolant level. I filled the rad up the next day, and drove around like a 1/2hr. Didnt overheat, but it ran ruff at idle, and stalled a couple times while parking it. I checked the coolant next day and i had lost about 1qt. I had engine codes 0302,0316 and pending 0171,0300,0306. Yesterday I checked the spark plugs, they were clean and appeared to be relatively new, and replaced the plug wires. Started it and got cel codes 0300,0302,0316 and pending 0171,0305,0306. I think the 0305 and 0306 is because i had gotten two of the plug wires crossed but then corrected it. The coil pack also appears to be working fine.
I checked vacuum system for leaks, visually and with the carb cleaner method. No leaks apparent. Plugged in the code reader and drove it for a few minutes. Vacuunm was 17+in. Hg. At idle; under load it dropped to 5 or less. Also since it overheated i have not detected the aforementioned issue with the 'lurch'.
I am really stumped and would appreciate any insight as I cannot afford to have this truck sitting around. I apologise for going on so long, but I think it was all pertinent information. Any questions or additional information needed, just ask. Thanks

 

Welcome to the forum

Are you still losing coolant?

P0171 code means O2 sensor is showing Lean on Passenger side of engine(cylinders 1,2 3), and computer is adding more fuel to balance it, so engine is not actually running lean

An O2 sensor reads Oxygen levels in exhaust, high oxygen = lean, low oxygen = rich
A misfire means NO Oxygen was burned/used up so it is dumped into the exhaust, so the Lean code could be because of the misfire, not the cause of the misfire

May be a head gasket leak at #2, what did the spark plug tip look like in #2, compare it to #4, 5 or 6, if coolant is leaking in then #2 will look steam cleaned, brand new.
Start cold engine with rad cap off, rad should be topped up all the way
Let it idle for a few minutes, if coolant starts to flow out of open cap then you do have a head gasket leak
You can do the Glove Test to confirm and also ID the cylinder with the leak, search for Glove test here, I have posted it meany times

17" of vacuum is low for sea level to 1,000ft elevation, expected is 18-21"
What year is the Ranger/engine?

Is the vacuum steady or does it drift?

 

Hi thank you for responding. 05 is the year. Yes I'm still loosing coolant. Between yesterday and the day before, i drove it maybe 5 or ten minutes, just enought to get the system up to temp plus a few minutes after that. I lost I'm guessing 10 to 12 ounces of coolant from the overflow tank. The rad was completely full.
I just started it cold without rad cap. Within a minute coolant had very slowly started to come put the top. My question is wouldn't this be normal, since the coolant starts heating/ expandingright away? I also just did the glove test exactly as prescribed, and the glove did NOT move at all.
the spark plugs all had an identical appearance and showed no evidence of coolant in the cylinder.
if memory serves, the vacuum reading was about 17 in. Upon startup ,and then went up to around 20 or so. I believe it was steady. Thanks again for your help!

 

Yes, some coolant will come out as coolant in the head heats up, if there was a cylinder leak it come out very fast.

Glove test is 100% accurate so you are OK for head gasket or cracked head issue

But coolant has to be going somewhere, can you smell exhaust, is there a sweet odor, like coolant

On a V6 coolant passes thru the lower intake from one head to the other, so it is possible for coolant to get into the air passages and when you burn coolant you make extra oxygen in the exhaust

I would focus on finding that coolant leak
You can rent a pressure kit that attaches to rad cap opening, it has a gauge and hand pump, you pump up system to 25psi and then watch to see if its dropping, if so there is a leak
And much easier to find that leak on a COLD engine, if its external

You can also add a UV Dye to coolant and then look for trails after running engine a few times, using UV flash light

 

Also no coolant in the oil or vice versa.
I will put a piece of cardboard under it tonight to check for externall leaks.
I haven't done anything with the fuel injectors or anything yet, but (again, correct me if I'm wrong ) i would think that a issue with the fuel would cause it to run rough at all speeds. Such is not the case with my problem. It sounds and feels fine at anything above 1100rpm. It does not hesitate or stumble at all with even heavy acceleration.

 

The exhaust smells fine, there is white smoke on startup and a sometimes a little bit as it idles but I'm pretty sure that is normal. I will test the pressure of the coolant system.

 

Yes, burning gasoline(H) with air(O) generates H2O(water), which is why exhaust systems rust from the inside out
So white smoke is common on startup hot exhaust is vaporizes the left over water in the exhaust from last time it was driven, and then it should stop, but if air temp is cold enough then the current water vapor generated by running engine will condense as soon as it exits the tail pipe

Cylinder fires because of 3 things, and misfires from the lack one, or more, of those things
1, Spark, at the right time
2. Air:fuel mix, in the correct ratio
3. compression, above 120psi

Compression is one of the things that can't be intermittent, well can be but rarely, so even though its a pain to test it, it can be done to take it off the table and focus on spark or fuel
You can of course start with spark and fuel, but you will waste time and money if it is a compression issue

 

The coolant leak appears to be on the front of the block, in the vicinity of the timing cover. It could be a little higher up on the front of the right hand cylinder head, but I cant tell for sure. I cant see the actuall leak, just the slight drip trail.
I will do a compression test tonight and post the results .

 

compression test results...
cylinder #:
1. 165psi
2. 90psi
3. 130psi
4. 150psi
5. 110psi
6. 100psi

the compression came up rapidly on all of the cylinders; I believe this means either head gaskets or valves, doesn't it?

 

You should do a WET test after another DRY test

WET test is when you put about a teaspoon of oil down spark plug hole and test

I use a straw, dip it in a bottle of oil put finger over the top and put it in spark plug hole
Then test
The oil acts as a seal for the RINGS, not the valves
The reading will always go up from dry test, but by how much will reveal if it is rings or valves that are leaking the most


There is a TSB for 2004-2006 Ranger 3.0l engines regarding exhaust valve seats
TSB here: https://therangerstation.com/ford_ra..._05-26-3.shtml

Your dry numbers would point to this issue, unfortunately that means new heads

 

Can I do the wet test cold? PITB trying to work in there without burning myself on the exhaust manifolds...

 

Yes, always do compression tests cold, dry or wet

Hot testing is for advanced results and of no value in this situation

 

Another dry test produced basically the same results. No significant change with wet test. That means three possibilities: valves, cracked or warped heads, or blown head gasket. Guess I will start pulling it apart this week. Thanks for all your help RonD!

 

Bummer, but at least you are not wasting time, or money, on non-fixs