CXL 2.0 Turbo Spark Knock

Spark Knock


If the vehicle has the 2.0L L4 engine
(VIN Code V), use premium
unleaded gasoline with a posted
octane rating of 91 or higher.
You can also use regular unleaded
gasoline rated at 87 octane or
higher, but the vehicle's acceleration
could be slightly reduced, and a
slight audible knocking noise,
commonly referred to as spark
knock, might be heard.This is from the manual on page 9-45 .
Hope this answers your question... I only use Premium and have had no problems with knock...

It actually isn't a mis-fire it is the fuel detonating before the engine is in the right position as far as timing goes. Basically the spark plugs are not what is igniting the fuel. When this happens the engine will retard the timing. The biggest danger is to the head gasket. Too much detonation will cause the head gasket to blow.

The first thing you should try is some fuel treatment. If you have a carbon build up inside the cylinder it may remain hot enough to ignite the fuel. I am able to run 87 octane fuel in our 2011 Regal but I only by gas from certain gas stations. I tend to stay away from the old run down stations just because if the the building and pumps are old the tanks will probably be old and leaking as well. You wouldn't eat at a old run down restaurant would you?

E85 will take care of this but you will lose fuel economy and it is harder to find is some areas. Another fix is to run fuel with higher octane or get a methanol/alcohol or water injection system. I run a alkycontrol system on my Grand National. This allows me to run 24psi of boost with out the knock. Without the methanol the car will only handle 18psi. In the older Turbo Regals we run a 160 degree thermostat to help keep the engine temps down and that is why Buick has the newer ones running at 185 degrees. We have found in the older Regals that they have less knock and make more power between 160 and 180 degrees.

Now to the scarier thought. Your fuel pump may not be putting out enough volume. Your fuel pressure should raise one psi per one pound of boost. If not it will cause a lean condition which will cause knock as well. Forced induction is great when it is working but when there is a problem it sucks. I am speaking from experience.

Like I said above, try some fuel treatments and get a higher quality of fuel from a quality gas station.

With these cars it could be a million things causing knock but this is the easiest thing you can try.