spark knocks

[cbailey]

I have a 89 caprice with a 305tbi that will spark knock if you burn anything in it but premium gas. I have put in new plugs but havent checked the timming. I purchased the car from an older lady when it had 89,000 miles on it and she had always used premium since the day she purchased it new. It now has 150,000 on and I have tried burning reg. or plus from time to time since i've had it but it just don't like it. Is this a timming issue or something else, I was told that the timming was computer controlled so I didn't know if I could adjust it or not.

p.s. I am a ford man but this car is my baby and i have to take care of my baby

[CD Smalley]

Probably is a timing issue. I run 87 in my 89 9C1 with no problems. Base timing should be set @ 0*BTDC with the EST wire disconnected.

I'd also run a can of GM Top Engine Cleaner thru the car too to remove carbon deposits. Get the aeresol version if at all possible.

[PeteA216]

Definately try cleaner, and if the timing is correct, try to retard it very slightly.

[RageCage]

It *could* be you're running too hot. Hot enough to cause knock, but
not hot enough to make the light come on. I had knock for years, at just off idle, when the engine had warmed up. Tried everything mentioned above, nothing worked. Finally replaced old radiator, which had had a few bottles of Bars Leak used in it, with brand new 3-row rad, and knock went away immediately. I was running hot enough to cause spark, but not hot enough to make the light come on.

[MT-2500]

If the timming checks out and still spark knocks check the egr valve operation and egr valve intake passages.
Mt