SHO engine troubles

[kryptto]

06/2015 55k miles - new plugs, trans fluid flushed.
12/2015 59k miles - antifreeze/coolant flushed/changed, thermostat housing/gasket replaced
04/2016 63k miles - new plugs
08/2017 79k miles - new plugs
07/2020 108k miles - new plugs
06/2023 122k miles - A/C recharge, New Alternator, rear shock absorbers
03/2024 -~123k miles - Differential Fluid Flushed/changed, rear diff serviced, trans fluid flushed, valve cover gaskets replaced.
04/2025 140k miles - (This is when we bought it) Oil and Filter, O2 sensor replaced, rear diff pinion seal replaced, new plugs.

This plug replacement, not good. These cars can go 80-100K before requiring if the car is not tuned.

 

[Junkyard_Mad-Scientist]

06/2015 55k miles - new plugs, trans fluid flushed.
12/2015 59k miles - antifreeze/coolant flushed/changed, thermostat housing/gasket replaced
04/2016 63k miles - new plugs
08/2017 79k miles - new plugs
07/2020 108k miles - new plugs
06/2023 122k miles - A/C recharge, New Alternator, rear shock absorbers
03/2024 -~123k miles - Differential Fluid Flushed/changed, rear diff serviced, trans fluid flushed, valve cover gaskets replaced.
04/2025 140k miles - (This is when we bought it) Oil and Filter, O2 sensor replaced, rear diff pinion seal replaced, new plugs.

This plug replacement, not good. These cars can go 80-100K before requiring if the car is not tuned.

I noticed that too, thought it seemed a little odd

 

[SHOCALL]

Also that the head gaskets were replaced recently. Maybe that job was unsuccessful?
Or the above coupled with multiple spark plug replacements, the mechanics just threw parts at an issue that was causing early death to the plugs. All the while not fixing the underlying and root cause.

 

[kryptto]

the mechanics just threw parts at an issue that was causing early death to the plugs. All the while not fixing the underlying and root cause

my guess too

 

[JonathanR]

We dug into it tonight again. Pretty sure we saw fuel injected into the cylinder with the plug removed when the fuel pump primed. Need to check on a few more things and possibly get a better borescope as the one I have is really hard to look around in the cylinder at the walls.

We removed the injectors and I’m going down that path after I get a better idea of the condition of cylinder 3. It was hard to see what I was looking at. It was damp and it did not smell like coolant. We will be able to compression test as well but did not do that tonight.

Thanks for the tips and we will update the thread and I’ll try and include some follow up for other people who end up down this path.

 

[kryptto]

good luck, the plugs were the mechanic avoiding the inevitable reality expensive conversation.

 

[luigisho]

If you get another borescope, it might have some value to look at the back of the intake valves and see how much carbon is on there. Just for reference as to when it might need a cleaning. There should be some posts regarding how to do this without removing a bunch of stuff.

 

[GreenEcko]

We boroscoped into my cylinder that was misfiring (cylinder 3) and I have some photos. Does anyone think if these are gouges or damage that is severe and if we should worry about cleaning this out or just do the injectors. Thank you for all of your help and suggestions.

 

[BradM]

The scoring looks as expected to me and I don't see evidence of a blown head gasket. You still have cross hatch too.

 

[luigisho]

Don't forget to change the oil after this. It likely has extra of fuel in it.

 

[JonathanR]

Replaced the fuel injectors in all 6 cylinders. Still running rough after reassembly.

We found an exhaust leak passenger side just behind the exhaust intermediary pipe and it was still blowing quite a bit of smoke. We also found oil below the LH turbo and when we removed the charge air pipe to examine it there was pooled oil in front of the blades but they still spun easily. If there was/is a bad turbo seal causing the leaking oil to be introduced I have a hard time wrapping my head around why only one cylinder would be misfiring. I don't want to keep blindly throwing parts at it but for sure we're going to replace that gasket on the exhaust and I am not sure what to do with the turbo situation.

I have some photos from the borescope but haven't pulled them into the computer yet.

Here's a shot from forscan showing cylinder 3 misfiring still.

https://imgur.com/JXSktX9

 

[Texas Marauder]

Have you done a compression test?

 

[Texas Marauder]

We also found oil below the LH turbo and when we removed the charge air pipe to examine it there was pooled oil in front of the blades but they still spun easily. If there was/is a bad turbo seal causing the leaking oil to be introduced I have a hard time wrapping my head around why only one cylinder would be misfiring. I don't want to keep blindly throwing parts at it but for sure we're going to replace that gasket on the exhaust and I am not sure what to do with the turbo situation.

At 142k it's probably time to replace the turbos. You don't say how much side or end play there is in the turbo bearing. This is a separate problem from the misfire.

 

[yaycandy]

Why would you blindly throw parts at it? Do a compression test and a leak down test to make sure ifs not the cylinder walls or a gunked up valve that is not closing fully as is common on gdi engines.

 

[GreenEcko]

We did a compression test on all cylinders, all were good besides cylinder 3 (misfiring cylinder) showed a value of like 2. We advanced the engine with the valve cover off, the camshaft lobes are moving and in good condition. The exahaust valve tappet were moving up and down. Any suggestions on what to try? This is a piece of debris found near the tappets, not sure what it is.

 

[JonathanR]

For clarification we checked all the cylinders and it appeared cylinder 3 had near zero compression.
Cylinder 2

Cylinder 3

 

[yaycandy]

For clarification we checked all the cylinders and it appeared cylinder 3 had near zero compression.
Cylinder 2
View attachment 94731
Cylinder 3
View attachment 94732

Thats good if its near zero, usually means its a valve no fully closing. When i scored my walls and had a dead misfire i still had upwards of 90psi. Remove the intake manifold and manually clean the valves with crc gdi intake valve and turbo cleaner spray. It works better visually than anything else on contact. Another easy way to tell if its blowing past the rings is run the engine at idle with the oil cap off, if you get oil on you then the rings or wall is bad and all that compression is going into the crankcase

 

[Texas Marauder]

I'm going to guess an exhaust valve problem. A borescope with a flexible head, 180 deg, can look up at the valves and possibly see a problem. A smoke machine should tell you which valve, intake or exhaust is the problem. Also, possibly a piston.

 

[GreenEcko]

Sorry for the late reply, little update on what has happened since the last post. We figured out it was a piston ring, so we got a new engine out of a 2010 MKS, took the old engine out, put it in. (I did some research and figured out that some sensors needed to be swapped, like the map sensor) we put the new engine in and it has been running perfectly. But I noticed that with a OBD2 scanner I could see my intake pressure. It scans and marks the highest pressure and the highest pressure I got was 29.2 PSI -14.7 is 14.5PSI of boost, I was looking around and found this likely indicates a tune, at first when I looked at my map sensor I thought it was a 2 bar because it never matched up to any pictures I found, then I did some more research and found out if it ends in AB then it is 3bar. (someone please confirm) I was wondering that this likely means my car is tuned and should I get it retuned because I don't know what octane or whatnot it is tuned on(I have been running 93 or 92 in it since I figured this out) What tuners are recommended). We also took my old engine apart and I have some pictures from that. Thank you all for your help! This community is very supportive and informative.

 

[kryptto]

3 bar and tuned read. this;

Any recognize this map part no

I'm fixing to buy a used mycal tuner, air raid cold air intake and that sensor. It's supposed to be a 3bar but it doesn't match part no. AA5A 9f479 AB Sent from my Moto Z (2) using Tapatalk

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