2015 Fiesta SE - Misfire on Cylinder 4 leads mid-travel leads to engine won't remain on

[CuriousGeorge]

Looking for some advice and whether another person has encountered a similar situation.

On the road today my 2015 Fiesta SE had the engine light come on, total loss of acceleration before what I would learn was cylinder 4 was not firing correctly. Ultimately the engine wouldn't turn on after I shut it off.

After getting it to a safe spot I was able to check the engine code P0304 was set. I tried replacing the spark plug on cylinder 4 and in the process observed oil on the threads and tip of the spark plug. It wasn't fuel. Changing the spark plug did not resolve the issue. When I tried to turn the engine on, it starts and sounds normal for a second before it just starts to fail then the motor starts knocking but by then it sounds like the engine was cutoff. Unfortunately even after this, there was no engine code set.

The fuel itself has been in my tank for a few days without issue until the issue started.

 

[econoboxrocks]

I'd change the coil pack too.

 

[Handy Andy]

P0304 is a Generic code for cylinder 4 misfire - so that's spot on, but as to what caused this?

Might be more of a spark coil unit and the spark plug. Wiring to the coil unit isn't difficult - it's 5 wires, with four of them representing the coil of the plug to fire and the last one a Grounding point.

So, for this to happen - and now a non-start or run issue - the code can be cleared but this may be more of a faulty coil pack or plug wire.

But also, could be an indication of a plugged PCV valve - because you mentioned you had oil around the tip of the plug.

Look into the well of where the plug rests - if a seal is failing - oil would flood that well - for the seal to fail - and nowhere else - might indicate a plugged up PCV valve that when enough pressure built up - the seal blew. If you can't find it anywhere else this usually tells me it was a one time moment that caused the failure. You live in cold climate so icing and plugging of the PCV line from water vapors and or thick oil getting sucked into the valve from the piston blowby - can also generate this, as a once in it's lifetime moment - and you have a valve cover seal blown out due to that.

 

[CuriousGeorge]

Thank you @econoboxrocks and @Handy Andy for your guidance. Using the new spark plug on cylinder 4, I was able to witness the spark outside the cylinder. I didn't observe any oil on the top portion of the spark plug, only on the bottom.

I tried to measure the compression across the four cylinders and only got about 48lbs which I hear is about 100 less than it should be but I'm not sure if at this point if this is the actual value or my battery just wasn't putting out the amps needed to turn the engine over. I've got the battery on the charger for now.

 

[econoboxrocks]

Fingers crossed.

 

[LionsTooth]

Well, thinking about this, compression is compression no matter how fast you turn the motor. The cylinder either seals or it doesn't.

 

[CuriousGeorge]

Well, thinking about this, compression is compression no matter how fast you turn the motor. The cylinder either seals or it doesn't.

That is a good point. Either my gauge is bad or the motor is leaking across all four cylinders.

 

[LionsTooth]

Sounds like the gauge to me. If they are all the same compression that would be very suspicious. How could that be right? All the same? Should vary slightly, at least. But all the same?....gauge.

 

[scotman]

15% difference is the general rule for compression variance limit across the cylinder bank.
Fiesta 1.6 has relatively high compression and also uses low drag type piston ring design.
I am intrigued to see how the rings hold up as miles pile up. So far, the highest mileage Fiesta i have seen was near 240,000. It didn't appear to have had top end work done. But, it did have a replacement water pump and timing set.

 

[Handy Andy]

Now this brings up another issue, did you have an opportunity to pull the front plastic cover off the Timing belt?

The Tell-Tale would be there - if you can't turn the crank in any sort of way to make the timing marks match, then the mess becomes far worse, as in a jumped time and possible damaged valve or cylinder - leading to low compression on ALL cylinders. - Valves won't close completely during compression stroke.

Or if they do, they are at the wrong point in the rotation aspect - closing at the wrong point.

You should or could, have more "pending DTC's" if the timing was really bad.

 

[CuriousGeorge]

Appreciate the suggestion @Handy Andy - I will look at pulling the cover off to check the timing belt.

 

[Handy Andy]

Keep us posted, this is a unique one...

 

[CuriousGeorge]

Small update, ordered a tool to use FORScan to try and discover any hidden DTC codes that might help point me in the right direction. Weather hasn't been great, slowing down progress.

 

[CuriousGeorge]

Another update:

Probably shouldn't have taken as long as it did but I finally have the OBDLinkEX and have connected it up to my Fiesta to use FORScan. Sadly there were no DTCs present that appeared relevant - only had a few that likely were from the factory. I used some of the module tests and they returned back with no errors found. Going to continue my investigation on the vehicle tomorrow. Hoping maybe the tool will shed some light on the situation as I try running the compression test with a new gauge. Also plan on checking the timing belt!

I appreciate the input from everyone thus far and I hope that by sharing these updates it will help another individual in the future if they come across the same or a similar issue.

 

[Handy Andy]

When you have time, tell us more about your FORscan experiences too...

There's a lot of us in the USA that see/hear about these devices, but that they work on changing "bits" on a BYTE word - which means an address map - which when in machine code language, it becomes a location of this address lets you do this if you change this BINARY "10001101" and ADD 32 (010000) - you can do disastrous things to the programming rendering the car unable to run by doing it. Is that 32 DECIMAL or 32 in HEXADECIMAL (which 32 in DEC is 20 in HEX?)

So yes, we certainly are keeping watch on this thread.

 

[CuriousGeorge]

Looks like the cylinder compression is fine. Tried to look at the timing belt but the way the cover was, there was no easy way to remove as it runs down the side of the engine. Started looking at the fuel supply. Disconnected, it seems to pump enough fuel though I need to buy a pressure gauge to find out what the pressure is. Wondering if this might be why the engine won't stay on. Being a long-weekend I will have to wait a few days to be able to purchase the gauge before I move onto buying a coil pack.

 

[CuriousGeorge]

Checked the resistance on the coil pack and found no irregularities but I installed a new coil pack just in case. This made no difference. Checked the fuel pressure and found no issues. The gasoline itself seemed suspicious so I emptied the entire tank and wiped it dry before refilling it with new petrol. During this process I also cleared out the line running from the rear to the front. The engine still won't start... no weird noises... just an engine trying to start. Odd thing, it has gone from being able to run for a few seconds to not at all. Plan on clearing out the rail and injectors next - hoping it is just a clog and we can be off to the races.

 

[CuriousGeorge]

Someone poured something into my fuel tank. Fortunately it stopped my engine from running instead of damaging the engine.

 

[LionsTooth]

Someone poured something into my fuel tank. Fortunately it stopped my engine from running instead of damaging the engine.

How did you determine the gas issue?

 

[CuriousGeorge]

How did you determine the gas issue?

When I had disconnected the line from the joint to the fuel rail, I noticed how murky the fuel was with what looked like water suspended in it. It wasn't the only path I was following at the time but it was a lead I kept pursuing until I got to the tank. It was more obvious something was wrong when I took a sample from the tank directly and compared it to some fuel I had aside in a gas can. As for the who and why, I'm struggling on that front.