Got the new motor fired yesterday and seemed to run ok. Went and got fuel sync set and drove around to break it in. Towards the end of the day it threw a couple codes, po172 and po351. po351 I understand is because I don't have a tach adapter on my MSD box.
Got up this morning and fired it up and it was running like shit, very rich like 11.7 at idle. Stunk the garage up and fouled the plugs. My base tune is closed loop and Sean said we may have to go with open loop tuning. That's all good but why the hell would it run ok in closed loop one day and the next morning run pig rich.
Any thoughts, aside from a possible tuning issue, on what to check? po351 points towards the coil so could that indicate a problem with the coil other than not having a tach adapter?