89 mustang mspnp2 surges in park


New Member
Nov 20, 2021
st.louis, mo
89 GT with stock heads and cam, performer rpm intake, 70 mm throttle body, on3 turbo, 50 lb injectors. Starts and drives pretty well. The issue I have is after it is warmed up it surges in park or neutral, in drive do not notice surging. A/F goes with surge, but have not had any success with modifying tables to correct. Attaching tune and log, any help would be appreciated.


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Turn off EGO correction at idle until you get this sorted, I personally leave my threshold at 1200rpm. Also shoot for a slightly rich idle, at least initially to make it less finiky. Shoot for 13.5-14.

The idle valve closed/open duty are set at 0/100, these values need to be set correctly.

You have drastic swings in the VE table in/near the idle cells, these transitions need to be cleaned up. The VE table in general needs alot of work.