JonnyBlazeGT

Took my car in today to have my buddy install my 3.73's. After he installed them he took it for a test drive. When he came back he said that my car has wicked bad spark knock. Asked me what I was running for fuel and I told him reg. 87 and that I was running the SCT 87 tune. He told me to go fill it up with 93.


SO, I did. I still had a half tank of 87. Should I be concerned at all??? I have new motorcraft platinum plugs, msd cops, and a bbk 73mm TB/Tube on the way.


Is the SCT causing the spark knock?


Also, he noticed my pcv hosed was collapsed and causing oil to blow all over the passenger side valve cover, so he replaced that.


BTW, he chirped 4th with the new gears on his test drive. Lol. It pulls a lot harder and I noticed my rpms are higher than they were but don't notice much of a difference while cruising. I guess I need to learn how to drive it right.

JonnyBlazeGT

I have a datalog file if anyone is interested. All jibberish to me.

jwog666

spark knock can be cause by several things, low octane, an inoperative egr system, too much timing advance, carbon buildup in combustion chambers, and engine temp too high for the amount of timing being run in the tune. dont worry about mixing grades of fuel, by the second tank full you will have switched over to 93 completely. but.....if you do hear spark knock get off the throttle immediately as the 4.6l in the mustang has no knock sensor and will not detect and pull timing to stop the knock.

JonnyBlazeGT

The problem is, Im hard of hearing and wear a hearing aid and I never even heard this. He is the first person to drive the car since I bought it. He said he hears it under a load. For all I know it could be gone now since I filled it with 93. I have no idea. I just don't want to damage anything.