I recently got an SCT tuner from American Muscle and put the tune on my car. Now for some reason the engine makes a light rattling sound when I give it half throttle. I'm not sure what it could be and was wondering if anyone else had an experience like this? My mom was riding with me and heard the noise too, and she said it sounded like a previous car she had and a mechanic told her it was "spark knock." Anyone got any ideas, or some things I could check/replace?

 

did you switch to premium fuel? sounds like you're getting detonation

 

I've always used 93 octane. It doesn't seem like detonation though, and it's not like tuners bump timing that much. I don't know how harsh detonation is because I've never experienced it before, but this doesn't seem that harsh, although that was my first thoughts about it, especially when my mom said spark knock.How would you describe detonation?

 

I would return the ECU back to stock tune to see if that fixes the problem. If it does then it's detonation...are you sure you have 93 in the tank? Maybe you got some bad gas...

 

I always get 93, and I doubt I got the wrong grade. I'm filling it up again tonight so we'll see. I remember reading tuners only advance timing 1 or 2 degrees, so I couldn't see that being the reason. It is also a light sound. How loud is detonation? It seems like you would notice you had, lol, but idk from experience.

 

Sounds like detonation to me. Try another gas station with 93 and see if it helps. Detonation is not always loud

 

if you have a tune and you dont use prem. you are asking for engine problems, watch it!!!!! you might have to advance the spark to ignite that cylynder at the right time, otherwise the slightest imbalance on a mustang is noticable, you see mustangs dont have a "harmonic balancer" they are internally ballanced, so your going to feel ANY misfire

 

+1 to lizzy, it can be anything from a small tick to the entire engine bay shaking go to a different gas station, find a kwicktrip, they have top tier 93 gas with NO ethinol,.. it works quite well

 

Well I'm filling up soon, so I'll just see if it keeps on. I've been told before you could bump timing several degrees before detonation, so I didn't think 1 or 2 degrees would cause it. We'll see.

We don't have those around here. We have Texaco, Citgo, BP, Amaco, Shell, and Exon. Which of those are good?