S420 Pinging - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 03-24-2004, 05:25 AM Thread Starter
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Date registered: Mar 2004
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S420 Pinging

I have a 1997 S420 and it has recently started valve pinging. Have put in premium and mid-grade gas, but no change. Is there a "brand" of gas that is better than another and which grade will stop ping? Also, will an octance booster help? Other than that is my next step the mechanic? Thanks from the new kid on the block.
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post #2 of 3 (permalink) Old 03-26-2004, 12:16 PM
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RE: S420 Pinging

First of all - your magnificent M119 engine in that car should always get premium. It's a high compression and it needs it.

Second - your car has what's known as a "knock sensor" on it - that "listens" for engine knock and electronically retartds the ignition to eliminate knocking.

It sounds like the knock sensor isn't functioning - or the computer isn't doing what it should when the sensor tells it that the car's knocking.

I say that you should take the car to the mechanic. Knocking can damage an engine. Your engine should never knock - even if you put crap gas in it.

1995 E420 78k
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post #3 of 3 (permalink) Old 03-30-2004, 10:47 AM
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RE: S420 Pinging

By the way, it's not your valves that are making the pinging sound. It's what's known as pre-ignition. the fuel mixture in the cylinder is igniting before the spark fires. As the mixture ignites, the plug fires, creating a secondary explosion which causing the "pinging" sound. Get your knock sensors checked immediately!
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