1999 Dodge Durango - spark knock problem

I have a spark knock that is consistantly making noise when accelerating. I've had the engine tuned up, timing checked, fuel rails cleaned, and the
spark knock went away for about 3,000 miles. It is back. After talking with a couple of other owners of 1999 Dodge Durangos it seems they are experiencing the same problem. Anybody have any wisdom they'd like to offer? Help!
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Checked for an intake plenum gasket leak? Pull the PCV valve out of the valve cover, and cover the hole with your thumb. Check for vacuum there with the engine running. If you feel vacuum, your plenum gasket is leaking, and the knocking is from carbon deposits caused by burning oil in the combustion chambers. The fix involved removing the intake manifold, replacing the gasket, and cleaning the combustion chambers with CC cleaner (then changing the plugs, as the CC treatment usually fouls 'em pretty bad)
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"Tom Lawrence" wrote:

What people will do to try to keep using 87 octane in a newer truck. 87 is not enough octane for a modern engine to do its best on a hot day and it is pinging because it is so bad that the ECM cannot retard spark enough to control it. Every time the ECM retards spark you lose power and MPG. Run a tank of 89 or 93 through it and see and feel the difference and forget about the smoke and mirrors to make 87 work on ahot day. You will like find it cheaper to drive it will better gas too given todays prices and a possible 5 to 10% improvment in MPG from better fuel requiring little or no retarding of the spark.
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How many times do I have to tell you? There is no spark retard in response to knocking in the 3.9/5.2/5.9/8.0L engines.

Fixing a blown plenum gasket is not "smoke and mirrors", and ignoring it in favor of a higher-than-needed octane fuel will only allow the problem to worsen.
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There is a hundred posts that will warn you of getting a dealer to flash the pcm. This will and has cost about 50% of our horsepower. The engine won't run on less then 89 octane. The flash will retard your spark and you wont have a ping but your cruise will be searching for a gear on the highway because it won't maintain overdrive with so little horsepower. The dealer will not flash it back. Anyway that is an easy fix, but the real problem is all that heat under the hood. After the 6 years it is really taken a toll. 160thermostat is too cold in the winter is replacing my undersized radiator the real answer?
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group.com> says...

I kind of doubt a radiator is the answer/problem. My old 77 360 pinged like crazy. A jet change to one size bigger helped as much as anything else I had tried, except taking 4 degrees off the timing, and that made the truck really gutless on the low end, and it was a slug anyway.
What seemed to help more than anything was when I went to a colder plug. With the leaded premium they had then, I could run a 180 stat, advance the timing 2 degrees over stock, and be totally ping free, even taking about 1000 pounds of junk up I15 to Los Angeles in the summer. If it didn't ping then, it wasn't going to.
The only pinging it did after that was when it started eating intake gaskets. What a hassle that was. I did get pretty fast at changing them, until I solved the problem once and for all with some horrible smelling gasket sealer stuff.
Might be worth a shot, plugs are cheap, you would probably have to order them though..
BDK
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"99scanner" wrote:

Let me get this one straight, a flash that retards spark to elimnate ping but needs at least 89 octane too? YOu need to get your facts striaght. If there is such a flash it is to run 87 octane and not ping and it would reduce power and MPG more. Just leave ECM flash stock and use 89 or better in warmer months and be done with this.
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I agree, back in the day they tried to convince you 87 was fine.
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