[eagleuh1]

My wifes mustang is starting to detonate real bad, even under light loads, such as flat ground and light acceleration. She usually runs regular grade gas. I have her putting high test in until I can have the time to check her car out. It has 55,000 miles, 2000 model. Do these cars have knock sensors to retard timing when they detonate. If so a bad one might let this happen. What should I be checking? Thanks

[Cricket]

Don't know anything about a knock sensor, but just check the timing, and go from there to retard the timing.

[mdvaldosta]

No they don't have a knock sensor, only the DOHC engines do. It could be bad formulated gas or some other things (related to stuff that shouldn't be an issue on a stock engine).

Sometimes carbon build-up in the chamber area over time can cause an effective raise in compression ratio - hence needing to higher octane fuel. You could also try running a set of plugs 1 heat range cooler than stock. If the detonation is slight, doing this should fix the problem and allow you to run regular gas.