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Engine Knock and Ping
We're going to answer some e-mail this week from a viewer named Doug. He's asked: "what can you tell me about engine knock/ping? I have a 1996 Ford Crown Victoria and it knocks quite noticeable under load. It's mostly noticeable on level ground when accelerating. I've tried higher-octane fuel and that helps but I have to use 93-octane to get rid of most of the noise. At some times the thing sounds like a diesel." Well what I can tell you is that the fact that you've upped to octane and it has help to some extent means that you're somewhat on the right track. I think you've probably got a carbon problem in that engine, so I suggest you take the vehicle in and ask the mechanic to de-carbonize the engine. They'll run the engine on a concentrated cleaner that flushes the fuel injectors and also has a secondary affect of de-carbonizing the combustion chamber.
There is one other area where carbon could be a real problem in your engine, and that's the EGR valve: the exhaust, gas re-circulation valve. The plumbing to those valves and the valve itself tends to plug up with carbon especially on an older model vehicle. It's not uncommon to find that EGR valve completely blocked with carbon to the point where it's no longer functional. The engine will run without EGR flow but it will be extremely intolerant of low octane fuel. It's going to ping like crazy under load on low-octane fuel. We do get a lot of e-mail from people just like this one, so have it de-carbonized and ask your mechanic to verify that there is not only EGR opening but flow. If that valve is plunged the car will also fail an exhaust emission test al well. To ensure that the valve is working properly you can also have an emission test done on it. I think once you have the vehicle de-carbonized you can go down to lower grade octane with no knock or ping.
Till next time I'm Bill Gardiner for Motoring.
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