Burnt Valve?
 

So I'm not really all that tech saavy, but here is what I have going on.

2013 BRZ with 80k miles on it Out of Warranty :(.
-Had the high pressure fuel pump replaced early on due to the chirp noise (didn't fix it but I just learned to live with it)
-Transmission was replaced just shy of 60k miles due to a (known?) issue when shifting down from 6th to 5th around 58-62 mph. It would make a slight grind while shifting. Covered under warranty.
-Only mods are a Perrin catback exhaust and gold rims (wheels=speed)

Other than that I've had no issues with the car and never any CELs until now

Jan 30th I drove about 2.5 hours to catch a flight to Turkey for two weeks of military duty. Halfway through my drive the CEL came on. Car didn't seem to be driving any different at highway speed. I was using cruise control. As I was approaching my routine halfway stop point the CEL would start flashing about 6 or 7 times then go away. Then solid sometimes, then flashing. I stopped and that's when I noticed the idle was a bit rough. I turned it off to go grab a bite of food and make a quick download. When I started it back up it didn't really hesitate much, but the idle was rough, but now I had the CEL and the traction control light on.

I didn't have much choice but to continue on to my destination since military orders. It seemed to still drive okay but now I had the CEL, traction control light, and when I turned my cruise control on, the light came on but wouldn't actually cruise and the light wouldn't turn off either. Fast forward two weeks of it sitting at my unit area while I was away. No way for me to deal with it where I was, so I drove back home. It would stall when I went to idle.

Finally was able to get the dealer the next day. They pulled 6 codes (sorry I don't have the sheet with me right this second to give the exact codes, but I can in a bit). They were essentially as follows:
-Random/multiple cylinder misfires
-Cylinder 4 misfires
-startability (though it usually starts right up)
-a few codes relating to air-fuel blah blah

Dealer said it would be about $125 to diagnose, but called back later saying it was going to take a bit more time to diagnose and it was going to be ~$600 so I said whoa on that. Talked to the tech when I went back to dealership to get the car. He said he changed the spark plug (didn't mention if it was bad or fouled) to rule that out. Said the compression was good. Said he swapped the ignition coils but the same problem persisted on cylinder 4 only. I think he said his next steps were going to be taking the injectors and swapping to see if those were bad, but I just didn't like how they were going to be charging 600 for the troubleshooting and not actually repairing it or guarantee to find the problem.

Took it next door to work and had a local guy that seems to be knowledgeable, but I don't really know who or what to trust about it. After he looked at it for an hour or two, he said he swapped the coils around and that he was 100% sure it wasn't the coils. Said he tested the injector and that it was pulsing fine so he doesn't believe it was that. Then he said the vacuum for that cylinder was very low (is compression the same?) and came to the conclusion that he thinks there is a burnt valve.

Okay, sorry for all of that if it's confusing since I don't know a ton about it. At this point I'm not sure what to do. The dealer seemed to think that the compression and spark were fine, but didn't get to the injector. The other guy said everything was good except the vacuum. I've always had 93 gas in it (unless I got a bad tank of gas at some point). It's had every scheduled maintenance at the dealership, even the expensive 30k and 60k. I don't drive it like a maniac, thought I've gotten on it every once in a while. It's my daily driver and I've taken pretty good care of it, plus I have a car seat in the back which means I'm not stupid in it.

I saw the main CEL thread but per that TSB I'm not getting those codes listed. I read about the whole ECU flashing thing, but I tried to bring that up to the dealership and they dismissed it. Not sure if that would be it either.

I just wanted to get your guy's take on it before moving forward. Do I trust the non-dealer guy or let the dealership continue to rob me of money before possibly coming to the same conclusion as the other guy?

Dealer says compression fine. Other guy says vacuum low.... If the compression wasn't low it could be a burnt exhaust valve. The only way to confirm for sure is leakdown test. Not many "new age" techs are versed in old school engine diagnostics like the all important vacuum gauge. I've seen a coil be an issue before on an frs. My buddies that recently blew up lol. Personally Check fuel pressure. Check compression compared to other cylinders then leak down test.

So are compression and vacuum two different things?

Also I still think I'll run into the dealership wanting to go through their steps which just cost me way more. Be nice if they could just run a borescope like we do with our jet engines (I know, I know nothing of mechanics, yet I'm a jet engine mechanic in the AF).

Got the codes.

From Dealer
P0300 - Random/Multiple Cylinder misfire detected
P0304 - Cylinder 4 misfire detected
P219A - Air-Fuel ratio imbalance (Bank 1)
P1604 - Startability malfunction
P119F - Air-Fuel ratio imbalance for direct injection (Bank1 fluctuation engine speed)
P119E - Air-Fuel ratio imbalance for port injection (Bank1 fluctuation engine speed)

Additional codes when my buddy hooked up his reader (all above minus the startability code)
P0354 - Ignition coil D Primary/Secondary curcuit
P0087 - Fuel Rail/System pressure too low
P1235 - Intake Control Valve Solenoid Circuit Low (had to look this one up)

I took two seconds and googled an article for you.


http://www.gregsengine.com/cylinder-...n-testing.html

Just looked at the spark plug the dealer gave me from yesterday (it has about 20k miles on it), but it appears to be dry fouled if that info gives any other indication on what might be the issue.

Look at fuel system. Also look into avcs being stuck on intake or exhaust cam maybe keeping a valve open.

Couldn't have said it better myself. Most dealership born technicians these days are raised on service bulletins and other published manufacturer repair guides.

:sigh:

Did you ever resolve the problem?