Chronic preignition noise

[2X2KOB]

Otherwise known as knocking or pinging: The car is a 2000 Outback, Phase II 2.5, 4EAT, 110K miles. It has pinged since new, a little bit, usually when going uphill at low rpm, which is when you would sort of expect it.

 

When we took it to the dealer five years ago, they said "use better gas". Didn't think too much of that brilliant answer.

 

So, I've pretty much been ignoring the problem since then, except that last month I decided to change the knock sensor ($97) to see if that would help, and it did not, not a bit. It knocks bad on 87 octane, and just a little bit on 89.

 

So what's the deal? Should I expect it to knock like that? My other 2000 OB doesn't knock a bit, not even on 87 octane gas. What's your experience with this engine, and do you have any suggestions on fixing this? It can't be good for the engine, but it hasn't killed it yet obviously.

[nipper]

Otherwise known as knocking or pinging: The car is a 2000 Outback, Phase II 2.5, 4EAT, 110K miles. It has pinged since new, a little bit, usually when going uphill at low rpm, which is when you would sort of expect it.

 

When we took it to the dealer five years ago, they said "use better gas". Didn't think too much of that brilliant answer.

 

So, I've pretty much been ignoring the problem since then, except that last month I decided to change the knock sensor ($97) to see if that would help, and it did not, not a bit. It knocks bad on 87 octane, and just a little bit on 89.

 

So what's the deal? Should I expect it to knock like that? My other 2000 OB doesn't knock a bit, not even on 87 octane gas. What's your experience with this engine, and do you have any suggestions on fixing this? It can't be good for the engine, but it hasn't killed it yet obviously.

 

This is ping, not knock. There are huge differnces between the two. Cars run extreemly lean, and some cars ping more then others. Since you can reduce it using better gas, it is defanitly pingining. Pingining is caused by hot spot in the cylinders pre ignitinig the air/fuel mix,. This can be caused by one of those things, or carbon build up in the engine.

Since its been doing it since new, and now has 110,000 miles on it, its a little late to complain about it

i think you are going to have live with it, like you have for the past 6 years and 110K miles. If it just started, then i would suggest using an engine treatment to clean out the carbon. It obviously is not hurting the car.

The only thing i can think of, is to run a cooler heat range plug. Since it seems you drive a lot of highway miles, a cooler heat range plug MIGHT reduce it. A cooler range plug will drop the spark plug temperiture. Surprisingly the hpt spot that causes pre ignition can be the spark plug body itself.

http://www.ngk.com/charglossary.asp?kw=Heat+range

http://www.tpub.com/content/construction/14273/css/14273_64.htm

 

nipper

[2X2KOB]

Thanks for the detailed response. Next time I do plugs, I'll go one cooler on the heat range.