Hello All,
using Costco 91 fuel in Ontario
my 87 CSX with 2.5 TII, stock garrett with two piece and mildly ported head. FMIC worked well on stock type spark plug (Autolite 65)
After a engine rebuilt, forged Weisco pistons from TU, S60, 3" SV and the rest is as above. After the rebuild, I replace the stock SP wires/cap with an NGK and used NGK 97382 Iridium plug. So far so good. I am only running approx 12 psi at the moment, But I thought I would go back to the 65 plugs. The CEL was good until the engine was warm and then started to flash at times (turbonator flash CEL on knock) and I could feel a loss of power. Never flashed at idle but commonly on low part throttle, like leaving a stop sign in traffic. Many time stayed on under load going up a hill. I decided to try a colder champion 9y and results was the same. Uggg replaced with the NGK 97382 Iridium and we are now good.
Any ideas why??? even the colder 9 has issue.