Who's Good At Reading Plugs? Pics Inside

[Scootsmcgreggor]

Looking for plug reading wizards. These plugs are out of my ecoboost but posting here since response in the ecoboost subforum has been nil, and I'm sure there are a bunch of experienced guys in here.

Been having a rough idle during cold starts that resolves itself within 3-10 seconds. A somewhat common failure mode in ecoboost motors is the head gasket between cylinders. So I'm keeping an eye on it to see if its losing coolant. Got a cyl#2 misfire at my last track day which prompted my investigation into why that may have been. Cleared the code and its not reappeared since.

About 10k on these along with 8 track days. Compression on all cylinders is 172-178psi (perfectly healthy for this motor) and leakdown was <5% on all cylinders. Leakdown almost seems too good to be true for a motor with 40k miles and 10 track days on it. But with these leakdown numbers I don't know how it could be losing coolant via a compromised head gasket. Or could it?

Left to right Cyl 1 >4. So the one odd plug coincides with the misfiring cylinder. Does that plug look leaner than the rest perhaps? Tune is for 91oct and Fuel is 91oct with a bit of 100 unleaded for knock protection. Data logs all look normal.

Any thoughts welcome. Thanks in advance.

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[Strokerswild]

The three look more or less spot on. Usually cardboard brown is ideal, although fuel additives these days can affect reading of plugs.

Something is up on the oddball though. Usually if you have coolant in a cylinder you'll see sort of a chalky residue on the ground strap or center electrode; this isn't really evident in the pic. Burned coolant can also leave deposits on the porcelain around the center electrode which can result in hot spots that can cause a misfire or detonation though.

Have you swapped coil packs around to see if the issue moves accordingly?

 

[Andrew@Lethal]

Change the plugs and do an oil change on it. I would still continue to monitor for a possible gasket seepage. These motors are known for it.

 

[Scootsmcgreggor]

Thanks guys.

Since the misfire hasn’t come back I haven’t swapped coils but I can do it anyways. Will give that a shot.

With the leakdown results being good would there still be any value in a cooling system pressure test? I got a tester but none of the caps worked so can keep working to find one if the test would be of value.

 

[K4fxd]

pressure test is a good idea.

 

[Dave2013M3]

The 2nd one is lean

 

[K4fxd]

That or water vapor cleaning it.

 

[lew]

#2 is burning coolant or oil or a combination of both, due to seeping head gasket when engine is off and cooling down. The accumulation of deposits on the sparkplug threads indicates the seep wicking up the plug threads then burning off soon after start up. Looks like it is in the beginnings of gasket failure. Who knows how long the engine will compensate for this. You can bet you will have worse symptoms as the engine ages. Good luck.

 

[GregO]

Any thoughts welcome.

What gap are you set for ?
What max boost do you see ?

 

[Scootsmcgreggor]

#2 is burning coolant or oil or a combination of both, due to seeping head gasket when engine is off and cooling down. The accumulation of deposits on the sparkplug threads indicates the seep wicking up the plug threads then burning off soon after start up. Looks like it is in the beginnings of gasket failure. Who knows how long the engine will compensate for this. You can bet you will have worse symptoms as the engine ages. Good luck.

Thank you so much for the analysis and explanation.

Grabbing a new head gasket and some ca625 studs and will fix before my next track event.

 

[Scootsmcgreggor]

What air gap are you running ?

Plug gap? They went in at either 26 or 28 thousandths (can’t recall which) and came out at 31. New plugs gapped to 26 just went in.

 

[Dave2013M3]

That or water vapor cleaning it.

True although there will other signs such as loss in coolant as well as white smoke, neither of which the OP complained of.

 

[fmc_smt]

Cyl 2 is burning coolant . Bring it up to temp , pressure test it . Want to start test at temp and let it set for a cool down cycle. More then a 5 psi drop in 5 hours is an issue . If you do have a drop , remove and inspect with a bore scope . Most likely you will find coolant intrusion into the cyl .

 

[Scootsmcgreggor]

Thank you guys. I have since noticed some slow coolant loss and the top of that piston looks damp while others are dry. Head gasket and studs ordered, will get it fixed up.

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