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Re: Knock in engine Posted by Ari [Email] ![]() ![]() In Reply to: Knock in engine, larry, Sun, 2 Mar 2003 23:27:08 Members do not see ads below this line. - Help Keep This Site Online - Signup |
First recommendation is to ask this over on the NG900 board.
However - what do you mean by knock? Quite frankly, the engine should never knock, in terms of pre-detonation, ping, or the like. Knock is when the fuel detonates too early, usually due to too low an octane rating of the fuel for that particular engine. The octane rating required by the engine varies from engine to engine, but a NA NG900 should run fine on 87 octane. However, if you're running the wrong spark plug, or have a considerable carbon buildup on the pistons/head, it may be too much for the knock control systems in the engine to handle.
If you aren't running premium fuel (89 or 91 in the US), try running a tank and see if the problem goes away. If so, you just may need a higher octane fuel. Every engine is different, and some require higher octane as they age.
I'm wondering if you're really hearing knock or just some other engine noise. Knock is usually heard at low rpm while the engine is under great load, like accelerating up a hill. The Saab engine is a bit rattly at idle - the valves can rattle, and the injectors can also make a bit of a racket. If you're hearing a rattle at idle, that's not knock - that's just the engine.
posted by 192.249....
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