Need help, spark plug content inside...

Have a vehicle here (2012 Fiesta) which has been back 4-5 times for a Ck Eng Light. Misfire. We have replaced spark plug, fuel injector, wires, coil pack so far. Light came on again. Ford Hotline (technical support line) is of no help. The problem happens on first start when vehicle is cold and full open loop. Does not happen again when driving. Duplication of problem is very difficult as it's a very short duration issue. No signs of anything visible except discoloration of spark plug. All plugs have nice clean burn and smell like fuel. The plug from this cylinder has a brown/tan discoloration and smells burnt. Since we can't gather any data from the PCM or driveability monitors due to the short timeframe the issue occurs, we have nothing to go on.

PLEASE HELP ME!!!!!

Does this help?

https://lh3.ggpht.com/-13v-LZ4hDZ4/UQpt_ibFpVI/AAAAAAAACag/BqzfChP43Ck/s1600/spark-plug-reading-lg.jpg

Edit: In fact it sounds like you have an overheated plug and an intake leak might explain it with the replacements you've made, but that would be unusual on such a new car and you should notice a higher idle. Really seems like that cylinder is running too lean for some reason.

Sticky valve guide? Bad lifter?

No borescope to look at the top of the piston?

To me on the surface, it looks like a programming/wiring/sensor problem. It is losing the cam or crank at startup and then finding them again. Clearly it is a misfire that clears itself, but the light stays on until the key is cycled. BTDT. Is the tone wheel correct? Since the tone wheel deflection is how the PCM figures out if a misfire is occurring or not.....

Check this out, it's like a manual for your ECU:

http://www.motorcraftservice.com/vdirs/diagnostics/pdf/OBDSM1201_16.pdf

Search for "misfire"

You need an old priest and a young priest...

What oil are they running in it?

Running Motorcraft 5w20. Oil changes done here. 25k on the clock.

Just got some new info. Cyl #4 is the culprit, compressions are 150, 150, 150, and 180. Now what is making #4 higher compression?

In reply to Conquest351:

Oil.

Ranger50 wrote: In reply to Conquest351: Oil.

How is that happening? Not trying to be rude, can't convey tone over teh interwebz, but I'm just trying to understand. How is oil causing the problem?

That could explain it, does the spark plug look like the "ash-fouled" one in the diagram I linked to?

Oil could be causing the problem in two ways: Causing preignition and increasing compression. Both would produce an unstable engine speed on every rotation which would trigger the misfire error.

Conquest351 wrote:

Ranger50 wrote: In reply to Conquest351: Oil.

How is that happening? Not trying to be rude, can't convey tone over teh interwebz, but I'm just trying to understand. How is oil causing the problem?

Increases the sealing power of the rings. To determine if it is rings that are the culprit on a LOW cylinder on a compression test, what do you use to see if it really is the rings? Oil squirted down into the cylinder. The oil fills in all the "holes" for the compression to escape.

That is why I asked if you had stuck a borescope down the park plug hole to look at the top of the piston.

Ranger50 wrote: Increases the sealing power of the rings.

Or even just by taking up space inside the combustion chamber.

Funny thing is, all the plugs look like the ones with detonation except #4 and it looks normal with a slight brownish discoloration and burned smell. All the others are clean and have a slight fuel smell, that's it. No excessive buildup on the plugs at all.

I'll see if we can get a bore scope in there real quick.

Ranger50 wrote: In reply to Conquest351: Oil.

I think he's nailed this one. I am not familiar with this engine, but something is leaking oil into this cylinder.

Could you post pics of the #4 spark plug and one of the others? Try and take it close up, see if your camera has a macro mode.

I'm going with excessive carbon buildup on the valves in cylinder #4 for $200 Alex.

Where does the PCV hose connect to the intake? Given the amounts of oil I see being collected in catch cans connected to the PCV hose......

Welp, I tried to get pix of the plugs, camera fail. Phone camera is great for most things, spark plugs ain't one. Looked in the cylinders, #4 is wet. Wet wet. Accumulation in the valve reliefs and on top of the piston. Plug is dry as a bone though. Not any accumulation on the plug at all, just slightly browner than the others. Lemme see if I can get a pic with the plug on something... BRB.

Number 3 looks normal to me (there's no insulator chipping anywhere, right?). Number 4...I dunno. Looks kind of like the "splash fouled" one in the diagram.

Leaky valve cover gasket ?

I'm going to go with vacuum leak on that cylinder. Strange as it sounds, a vacuum leak can most definitely cause a rich running condition and additional carbon buildup which would explain the higher compressoin. I'd look for an intake gasket leak or, if the brake booster PCV etc is connected to that runner look for a vacuum leak in the hose/fitting/etc.

Does not seem to be any vacuum leaks. Verified with ether/carb cleaner. No lines to that runner at all either. Thinking we have a valve seal leaking or something along those lines. Waiting for warranty to approve further tear down.