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03:14:09 - 12/29/2024
Dakota Performance
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BobH
Dodge Dakota
10/21/2001
18:51:37
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 Subject: Spark knock returns
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Message:
Last March I purchased a 2000 Dak (3.9L) with 18K miles. I immediately noticed spark knock. I consulted this board and was advised to install Autolite 3923's, a 180 degree t-stat, or go to a high level octane (or some combination). I decided to go to 89 octane and it fixed the problem... or so I thought. The pinging started again about a month ago.
Question #1: What changed?? Did the computer get used to 89 and advanced the timing further?? I try very hard to be consistant with the brand of gas I use.
Question #2: I just today purchased a set of 3923's. The guy in the parts store said that installing a plug that was cooler than what was spec'ed would cause carbon build-up in the engine. Is that true?
Question #3: My local mechanic (not a Dodge dealer) said that he could retard the base timing by adjusting the distributor cap and that would help eliminate the ping. Is that possible??
I hate pinging and want to be rid of it, but I don't want to screw anything up.
Thanks!
Bob H.
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jay
Dodge Dakota
10/21/2001
22:19:00
|  RE: Spark knock returns
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Message:
ok here we go:
question #1: i could not tell you if anything has changed for i am not your mechanic, there are many possibilitys but 3.9l v6's do not have knock sensors so it really can't adjust the timing for differnet grades of fuel, the IAT sensor is mostly responsible for that. The IAT will adjust fuel and timing by the temp reading it recieves as air enters the intake ( hence this is why an IAT adjuster works so well ). The only reason higher octane fuel will reduce or rid your engine of knock or ping is because it burns slower and is less prone to preignition.
question #2: A cooler plug can sometimes foul out alot easier because it doesn't reach a high enough temp to burn it self clean at lower rpm ranges, but as far as carbon in the engine from cooler plugs i've never heard that and if anything you would end up with carbon fouling on the plugs, not in the engine. The autolite 3923's run good but if your engine does not ping then don't install them but if it does and in your case your truck does ping then install them. When i installed them on my truck that does not ping it seems as though my gas mileage went down, but if you have a problem then they should fix it and your gas mileage should actually be a bit better. Go to www.speedtweaks.net and download the instructions on how to reroute your coil wire, in some cases this seems to work on these engines, probably because the coil wire sits extremely close to the alternator and all of the other wires that some of the voltage may jump or arch on other wires or high voltage units.
question #3: you can not adjust timing by turning the distributor. The base timing is set by the pcm and you can not adjust it through the distributor.... DO NOT TURN THE DISTRIBUTOR AND DO NOT LET ANYONE ELSE TURN IT EITHER.... the only thing you can do by turning the distributor is adjust the fuel synchronization but this requires a DRB scan tool.. if you have to have a timing adjustment made you have to have your pcm reflashed at the dealer.
go to www.speedtweaks.net it's all in the tips and tricks section about all of these ?'s you have asked..... hope this helps
jay
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