Spark Knock ( pinging at low speed )

[mcgiverohno]

I have a 1991 Caddy Eldorado it has a spark knock at low speeds.
I am about to replace the EGR valve on it. ( this will be the 3 time this has been replaced in about 5 years. )
First two times was by a repair shop this time I will do it.
Is there anything els that would make this happen that I could fix.
Mcgiverohno

[RABarrett]

The problem here is why is it necessary to replace the EGR so frequently? Is there another problem here? Is the problem "trace knock?" "Trace knock" is the result of the timing advancing faster than the EGR valve can open , creating a slight knock during transient throttle maneuvers. The age of the engine may require a higher octane than was acceptable when new. It is also true that 89 octane fuel when your vehicle was new is now a lower octane now, requiring a higher octane rating. Is the emission system operating properly? I have seen several controls, which allow for preheating of the incoming air into the mainfold, to stay in effect, supoerheating the air, and causing this problem. It is also possible that another control is advancing the timing faster than originally programmed. Ray

[mcgiverohno]

I have allways used High Test gass 93 octane.
When hte car fist pinged serveral years earler the mechanic told me they changed the egr valve and it was fine for a couple of years.
The last time the ping started again took the car to the shop and the mechanic said the egr valve was leaking and replaced it again. Ping went a way for another year or two. Now it is back again.
A tec I talked to personaly said retail egr vales are not very good.
That I need to get an egr valve from GM. I did that but have not put it on yet. I hate to bring the car to caddilac because they wont to charge over $500.00 to do a tuneup. Just to fix the ping.