Chasing a misfire

[Djc94]

Ok having a problem maybe someone can help me out I recently bought a 2008 gti fsi motor and from the dealership I caught a misfire omw home and have been chasing it for almost two months. I’ve changed the spark plugs, coil packs, walnut blasted the intake valves, had the injectors rebuilt, oil change, cam follower inspected(it’s good), new alternator, replaced the pcv with a block off(gunna convert to a catch can soon). Any help or insight would be greatly appreciated. I shall also note that I have no loss in power while driving but cold starts is where the misfire happens.

 

[ROH ECHT]

Do you have a fault code scan?
Does it show the misfire codes being stored at low rpms?

If it stumbles mostly or only at start-up...then the runner flaps or throttle body may be the issue.
These will not light up a CEL, but they will store a code....so, scan the engine codes if you can.

 

[Djc94]

Do you have a fault code scan?
Does it show the misfire codes being stored at low rpms?

If it stumbles mostly or only at start-up...then the runner flaps or throttle body may be the issue.
These will not light up a CEL, but they will store a code....so, scan the engine codes if you can.

I have a cheap Walmart obd2 scanner so it won’t really tell me if it’s at low idle but it reads there’s a cylinder 1 misfire p0301 code.

 

[ROH ECHT]

OK, considering your list...if this were me; I would test compression at some point just to rule it out. I would remove and inspect the new spark plugs to compare #1 with the rest for running rich or lean/hot. Also, check the gap of each...no more than 0.031" or 0.8mm. Then make sure they are torqued the same at 22 lb*ft. Then test the N80; Do a draw test on the intake manifold side of it...my vid;

Then purchase one new genuine oem coil and try it on the #1 plug.
Following all of this, I would begin searching for leaks in all of the air inlet. If none of this fixes it...you will need VCDS for data viewing or take it to someone to locate the issue. Or, there may be an issue with the #1 injector.

Just one more thing you may want to consider; with a PCV-delete or catch-can, you want to make sure the rear crank-case breather tube has no valve in it. With a PCV-delete or catch-can it is best for it to not have the valve so you never need to worry about it sticking in its closed position. https://www.golfmkv.com/forums/index.php?threads/proper-pcv-to-crankcase-breather-tube-info.378931/

 

[Djc94]

Greatly appreciated I’ll definitely check the compression and check the plugs and coils. My buddy has VCDS so I’ll have him run a data check and keep you posted thanks again.