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Chasing a miss


wrayturbo
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High everyone,

I just finished my first Subaru build as I needed a fun dadmobile and came across a blown 05 lgt 5mt wagon. I just finished the motor and it is a complete rebuild with rebuilt oem heads, forged Icon pistons, arp rod bolts, arp head studs, Blouch 16g turbo, cleaned stock injectors, racer x front mount, 3" full exhaust, cold air Intake, AOS, and mishimoto inlet.

I'm having trouble getting this broken in as I'm fighting engine codes. After first start up I was getting a flashing engine light and cruise light. After a few drives I got a pffff and a p0011. As far as break in is concerned the car drives pretty normal and I'll notice a miss at the low end at times but for the most part it seems very eager. I replaced the OCV on bank 1 last night and did a data log. My AVCS seem to be syncing up much better now but I'm still seeing some variance. Is this enough to cause some missing is my question. I did rebuild the AVCS with the company 32 tool to clear debris. I have a new OEM one on hand to change this weekend if the numbers still look off. I may need to log fewer things for a better look so let me know if you need!

https://docs.google.com/spreadsheets/d/13mOqSHmNl7TCCAzVGn6ctOCAdaMW9tQPi2y1-GRCtao/edit?usp=sharing

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When your heads were installed did you use engine sealant very sparingly under the intake cam cap (the one with the mounting location of OCV)? There is an oil channel that feeds the AVCS gears. It is very easy to have too much sealant that blocks this channel when torquing down the cap.

 

If you swap OCVs and the issue doesn't follow then unfortunately the only way to know for sure is to remove the timing belt, cam gear and cam seal. Then use a flashlight to look in the channel.

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Try monitoring for cyl roughness. Did you get a missfire code like p303 etc? If one comes up rough then try the usual ... swapping coil, plug, injector, between a known good cylinder to see if roughness follows. Did you tgv delete? The left over connectors for tgv motor will plug into the injector (with a little force).. if so with key on, engine off you’ll hear the injector firing.
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I did use sealant sparingly but that's what I was worried about because what I consider sparingly may not be. I did rebuild the AVCS with the company 32 tool and wonder if it's not hanging in there. I have a new one i'll put it in today and see what happens. I'll set up the cylinder roughness but no... I have not had any misfire codes. I've scanned with AP and I have a snap-on enos scan tool.
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Are the misfires across all cylinders or were you able to narrow down which cylinder(s)? I used my AP set to monitor roughness by cylinder.

 

Not sure about those plugs.. but I’m a firm believer that NGK oem replacement is the way to go with subaru engines.

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When your heads were installed did you use engine sealant very sparingly under the intake cam cap (the one with the mounting location of OCV)? There is an oil channel that feeds the AVCS gears. It is very easy to have too much sealant that blocks this channel when torquing down the cap.

 

If you swap OCVs and the issue doesn't follow then unfortunately the only way to know for sure is to remove the timing belt, cam gear and cam seal. Then use a flashlight to look in the channel.

 

 

^this.

 

 

Also, just looked at your log. why are you AVCS advanced like that with barely any load on the engine? Was the engine cold during that latest log? Mine would be at zero with no load on the engine. But IIRC after a reset and during a cold idle, the AVCS will advance. But mine (stage 2) peak around 14-15 cold.

 

 

And really, a misfire count of 1 is nothing.

 

 

How are your long term fuel trims looking?

 

 

Finally, I would use OEM plugs.

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  • 2 weeks later...

Finally got some time over break to swap in proper oem plugs/ two good coils on cylinder 1 and 3 and while I was in there I did a compression and leak down test. Sure enough compression was 125-125-126-129

and the leak down showed a 20% loss. New build only has 300 miles and I would think that the rings would be seated by now. The car has Keith Black (Icon) forged pistons and I'll double check but I think they use a steel ring. Amsoil 30 weight break in oil has been used and now on second oil change of the same. I didn't have any babysitter time left to get a good bead on where the air was escaping today but considering the low compression across all cylinders I would expect rings or improper valve clearance. They were set to .007 intake and .012 exhaust. Thoughts?

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