Please help me diagnose a problem

[toyman]

Premium grade is a misnomer. The higher octane gas is a slower burning formulation. If yours is pinging then something is causing that occurrence. What is the timing set at? Factory is 10* BTDC but you can usually advance to about 13/14* without any pinging.

 

[Ryleighsdad]

Timing is at 12* How is premium a misnomer? I had a supercharged car that I ran premium in with no problem, run mid grade and that thing would detonate all day long. Even my mothers 2012 Murano runs crappy on mid grade. Race fuel is 100+ octane.

 

[toyman]

It's a misnomer in the context that premium is viewed as better than regular. That's not what octane numbers are about. High compression and supercharged engines need a slower burning formulation to properly burn in that environment. Engines are engineered to run on a particular octane. The 302 Ford was designed to run on 87 octane from the factory. Running a higher octane than is necessary besides wasting money may not gain any performance and may degrade performance due to incomplete combustion. My 2008 EB Expedition runs great on 87 octane, my 200 Chrysler 300M needs 89 octane and my blown mustang needs 94 octane.

 

[Ryleighsdad]

Well, all I know is Ive been running 93 with no problem, put 89 in it two days ago and got detonation.

 

[toyman]

Then you are just treating the symptom (pinging) and not getting to the cause/problem. Are you certain the HB hasn't started to fail and you are reading the timing correctly?

 

[ratio411]

Turned out the ign coil was breaking down under load. Swapped that an she runs like a scalded dog now! Thanks for your help.

I tried mid grade fuel Ratio, and she detonated like crazy! Had to add a can of octane booster to get it to stop. From here on out she gets premium. lol

If you need it, you need it!
The engine is probably not stock, assuming you don't have the timing too high or carbon deposits in the combustion chambers.

 

[Ryleighsdad]

As far as I know the internals are all stock, BBK cold air intake, and magnaflow exhaust are supposedly the only engine mods done, but who knows for sure. All I know is that it does not like mid grade fuel.