I own a 2001 Ford Ranger with the 3.0, Its got a misfire the P0305 which some times comes on and does not. Now when i drive once i get around 3.5k RPM or more i feel the misfire go away and power is restored. Im not sure what is going on, The wire is good and so is the spark plug. When i pull the spark plug out it is wet. it also looks like it maybe smoke from the tail pipe and there is moisture but it is winter and cold out so hard to tell. But im confused cause when driving or revving to a high RPM the misfire goes away for a bit, so does more in idle. any advice would be nice thanks.

 

if the plug is wet, then it sounds like either its leaking coolant or has a stuck open fuel injector, i would test the resistance of the injector, do a block test to ensure its not a blown head gasket letting coolant by soaking the plug. if block test stays blue, move to the injector for that cylinder, like i said before test the injector for good resistance, test them all to come up with a base line of what good resistance should be, look up on youtube for ways to test the flow pattern of the injector itself.

 

If possible do a compression check.
Remove all 6 spark plugs before the test
Write down results

3.0l has 9.3:1 compression ratio, so between sea level and 2,000ft elevation you would expect 165+ psi in each cylinder

#5 probably has low compression so air/fuel mix can't ignite until compression gets higher which comes at higher RPMs.

Just to take faulty coil pack off the table swap #1 and #5 wires on the coil pack, move #1 spark plug wire to where #5 is now and #5 to where #1 was.
They are right next to each other, and use the same coil, Ford uses a Waste Spark system; because of engine balancing #1 and #5 are at Top Dead Center(TDC) at the same time, one on compression stroke the other on exhaust stroke, Ford's system sparks both cylinders when at TDC, so one spark is "wasted", hence the name waste spark system, but as far as spark timing #1 and #5 are exactly the same so swapping them won't effect spark timing. (or swapping 2 with 6 or 3 with 4)
In the coil pack #1 and #5 are hooked up in Series electrically, that means one spark plug will spark from center to tip, and the other from tip to center.
If one coil in the pack gets high secondary resistance one spark plug can fail to fire until resistance is overcome by current, higher RPM can do that.
After swapping the wires and clearing the codes, if you start getting P0301 then problem has moved to #1 and Coil is the problem.
In the early 2000's Rangers with 3.0ls did get a batch of sub-standard coil packs, that did cause P030x codes, there was a TSB about it.

Block test is good to test for head gasket issue but costs money, Glove Test is better and is free.
Why is a blown head gasket even an issue?
A cylinder has 150+ psi when cranking, and over 900 psi when firing, if some of that pressure escapes via a gap(breach) in the head gasket it generally encounters a coolant passage since each cylinder is surrounded by coolant passages, whole point of the cooling system is to carry cylinder heat away.
The pressure in the cylinder is in the form of air(exhaust but still air not a fluid), if this air is pushed into cooling system it displaces coolant in the head(air rises in fluid), this can cause head/engine to overheat since air doesn't absorb heat like coolant does to carry it away, air also tends to stay in higher areas which prevents coolant from circulating as well.
This extra pressure in the cooling system can get above the Rad Caps 14psi rating, so needed coolant is pushed out of rad and into overflow tank, causing more overheating.
On intake stroke of effected cylinder some coolant can be sucked in, since coolant doesn't "burn" this can foul the air/fuel mix and cause a misfire, at higher RPM the "air" pushed out of cylinder would be sucked back in instead of coolant, so no misfire.

In the above you would notice over full overflow tank, and in the beginning warmer engine temp on gauge and heater might blow cold now and then because "air" is being pumped into the heater hoses instead of warm coolant.

Block Test uses a chemical reaction to test the "air" in the radiator for traces of exhaust, there should be none unless a cylinder has a "blown" head gasket and is pumping that "air" into cooling system.

Glove Test
Cold engine
Remove rad cap
Remove overflow hose from rad and plug that port in rad, vacuum cap or short hose with bolt in it works
Put latex glove over rad cap opening and seal it with rubber band, a balloon or even a condom will also work.

Unplug the connector on the coil pack, you want a no start

Crank engine and watch the glove, it should just lay there
If glove starts to bounce you have a head gasket leak, the 150+ psi pressure on compression stroke is being pumped into cooling system making glove bounce
Remove 1 spark plug at a time and crank engine again
When glove stops bouncing, the last spark plug removed was from the leaking cylinder, reinstall it to be sure.


To test for leaking fuel injector you can use the "Clear Flooded Engine" routine found in all fuel injection computers.
Key on engine off
Press gas pedal to the floor and hold it down all the way
Crank engine to start, keep holding gas pedal to the floor

Engine should NOT start, engine should NOT even fire a little, fuel injectors are shut off
If it starts or fires then fuel is leaking in.

Clear flooded engine routine uses TPS(throttle position sensor) voltage to initiate.
Key on = computer on and TPS is getting 5 volts, with throttle closed TPS sends computer back 1 volt
When you press the gas pedal to the floor, wide open throttle(WOT), the TPS sends computer above 4.5 volts.
With 4.5 volts from TPS and engine at 0 RPMs the computer enters Clear Flooded Engine mode, and shuts off fuel injector pulses, but spark is still on.
As soon as you release the gas pedal injectors will start working, even while cranking engine.
If you had a leaky fuel injector engine would fire because fuel is leaking in even through injectors are off.

And just a heads up, bad TPS or short between TPS wires can cause a No Start because of this.

 

Thanks for all that info, i have swapped plugs 1 and 5 same issue, i top off coolant and then it just overflows the overflow and i hear it bubble once engine is shutoff. so i am pretty sure its the head gasket i just do not have the funds and i dont want to get rid of the truck its still good. I have started a go fund me. Cause i dont want to lose this truck i have had it since 2007 and was my first vehicle. Thanks for the great advice was very helpfull. just wish it was something more simple. thanks again here is my go fund me, and thanks again.
https://www.gofundme.com/6bgzfqss

 

what in the hell lol... what is the limit of your gofundme 3k? theres no way it should cost that much unless you plan on going to the ford dealer and giving them a good size tip. any shop around should do it for around 1200-1800 at most and thats if its a 4.0L. i just did the head gaskets on my 98 3.0L cost me all of 450-600 to have it done, of course i did my own labor because i access to a full shop. but in the 10 years ive been a professional techn, never once have i seen a ranger leave the shop for a head gasket repair with a 3k bill attached too it.

 

I'm not sure if it's that much cause they said it might be 20 hours at $75 and hour now that I have more of a diagnosis.I need for them to look it up just wanted to make sure I just set it up for that just in case. Plus I don't know if the head is cracked or just the gasket or warped don't think it's that since it's only one cylinder.

 

HOLY HELL. the hell kind of shop are you going too... the book time on that repair isnt no where close to 20 hours unless your slow and you suck and you enjoy ripping off customers. book time for this repair is billable at 7 hours, although it only takes around 1.5 - 2 hours to complete. find a different shop bro.

 

Howzit going everyone, new at this forum. Was wondering if i could get an insight. My problem with my 97 ford ranger 3.0 started 2 weeks ago. Was climbing a hill one day after work and my temp gauge started climbing, before it got to high i pulled over and popped my hood, Found the radiator hissing. Got it to cool off and added some water with coolant and managed to drive it home, that afternoon, i found that the heater valve has sprung a leak and that must have been the reason why my coolant got drained. Anyhow, after that, my truck started acting up only on IDLE. on load while driving it's very smooth, then the day after my CEL started blinking. i pulled the codes and got a P0300 which is random misfire, Went to autozone and got new spark plug and gap it to .042 to .046. That did not solve the CEL issue. this time i got a P0301 and P0304 which of course misfire on CYL 1 and CYL 4. I then figured this might be more serious than i thought, so googled as much as i could. I did the carburetor cleaner test where i sprayed all the hoses, and all the intake side hoses for leaks and could not find any, I cleaned the MAF sensor, the IAC sensior and the EKG sensor, i also cleaned the ait filter, and double checked the fuel pressure to rule out fuel pump or fuel filter and with key on engine off i was getting 38 psi which slowly go down to 32 psi. I rechecked the plugs and I still got the same code. I then proceed to change the spark plug wires. Next day, i got the same code. I was then told to ohm out the coil pack. I was getting 14.5k ohm on all the coil pack terminals, but i went ahead and bought a new one anyhow. Next day, after clearing the code once again and they're back. I ohmed out the spark plug wires just to make sure and they were all in the neighborhood of 6.5 k ohms except for wire 2 which showed 5.1 k ohms, I once again tried the spray method and could not find any vacuum leak. i googled more and wanted to try the DIY smoke test. I made my own contraption and the only smoke that was coming out was on top of the IAC valve, but i was told this would not produce the code. at this point, i wanted to give up, after all , the car runs smooth and fast on load but just on Idle that it seems to shake a little more than before, OH and plus the CEL lights just annoys me. The only thing that i have not tested yet is the fuel injection which i have no idea on how to test. I was told that it could also be the CPU. Can anyone please tell me what or how to check the next thing. Mahalo from Hawaii

 

next thing you need to do is check the injectors on 1 and 4, use a noid light to verify the circuit is working, then ohm out the injectors, compare readings with a known good, if no issues is found there move onto a compression test, check each cylinder, disable the coil, turn the engine over 6 times per cylinder while checking pressures. most of the 3.0L ive torn down ive found suck valves, because the valve seats in these engines are trash.

 

Thank you for that reply, I will get a hold of a noid light and do the test. I can also ohm out each injectors and just compare the bad ones to a good one. But ar that, i think my limitations stops from there. i don't have the equipment to do a compression test and wouldn't that mean pulling out the head? anyhow, someone also told me that if i just pull out the wire from the injectors that i'm suppose to figure out by a certain sound which one is bad? I also saw on one the threads in here that if I swapped out the wires at the coil pack between cyl 1 and 5 since they fire the same time that i would know if the wires or the coil pack is bad and i got a random misfire as a the only code instead of the original misfire on 1 and 2 only. any tips on getting the injector connector for 5 since its under the throttle body? I guess i can just do the noid test on 1 and 4 then just pick one good one in the back where i might be able to access the injector harness.

 

Anyone knows what the resistance reading on a 3.0 ranger plug wires and coil pack should be?