causes of detonation?

[Scott]

what are some common causes of detonation? Ive been having this problem for a while, where i can hear it pinging a bit under load at low RPM's (so if im accelerationg up a hill below 3000 rpm)

Ive changed the fuel filter and plugs, ive jumped octanes and its still doing it with 89.

Any ideas? Im gonna put the scantool on it to see if the timing is out, but it is a DIS, and ive never adjusted the timing chain.

Are there any other things that can do it? Plugged cat? (my exhaust has sounded a little different for a while now too.

Thanks.

[THREE40SEVEN]

Some general ideas...
Excessive carbon in the combustion chamber
Bad sensor causing a lean condition (ect/act/o2 etc)
Crank trigger malfunction causing the ignition to advance..

Check for codes and see what comes up.

[cobber112879]

Have you disconnected your EGR system? Is your EGR system working properly?

[Scott]

Put an OBDII on it tonight, no codes were stored, and we ran through all the sensors, and everythign seemed ok.

Fucked if I know.....

who wants to buy a sunfire before the rod goes through the block?

[legendboy]

Too high of a static ignition timing will also cause this under high load at low rpm.

[stockEK]

High intake temperatures would also have an effect, albeit a small one. Is it worse when it is hotter outside? Aftermarket intake which sucks in hot air from the engine bay? Probably unlikey candidates, but they could play a role here.

Id lean towards a timing issue. The ECU should have enough adjustement range to compensate for these sorts of things.

Maybe the knock sensor is toast, and the ECU thinks everything is fine??

[Scott]

The knock sensor looked like it was doing its job when we had the scantool on it. It was reading the detonation and retarding timing accordingly.

The static timing isnt adjustable on the car, its a DIS system. I was given an idea by another guy to check for moisture in the coil packs and replace the springs in the plug boots.. I'll give that a try this weekend.

[DSMer4Life]

As THREE40SEVEN already mentioned, a build up of carbon deposits can cause hot spots in the combustion chamber and lead to detonation. Has a combustion chamber cleaning ever been done? It might not hurt to give it a try.

Also, are you using the proper heat range spark plug? If the spark plug can't absorb enough of the heat in the chamber (which is part of the plug's job), that may be a contributing factor to detonation as well.

[apollo guy]

yep ,i agree as well ,get a combustion chamber service done ,makes a world of difference ,enough build up will cause pre-ignition (ping) and will increase compression (seen double in some cases) will cost you about 90.00 or so .