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Jimmy9190
Dodge Dakota
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11/11/2007
19:13:27
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 Subject: Spark plugs and PCM's
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I have a 2001 3.9 V6 with 5-speed manual, 79,000 miles. It had a slight ping in the engine, not too bad but I decided to do a tune up anyway. I usually do it every 20,000 miles and it was just about time. So today I replaced the cap & rotor with the brass ones from Napa and put in the NGK FR5 plugs with a new set of the Napa premium Belden wires. Did an oil change today too. I was using the Autolite 3923's but I had read that the NGK's were better for the 3.9. The truck does seem to idle smoother and start easier, and there is a noticeable improvement in power on the butt-dyno. But the truck still has a moderate ping under a light throttle. My question is does the PCM need time to learn the new plugs due to the difference in spark from the V-Power NGK's? I have looked down the throttle body and there is a very light film of oil which I read is normal so I don't suspect the belly pan gasket. If I'm wrong about that hopefully someone here can tell me so. I take very good care of my truck and I use Chevron gas just about all the time, #87 octane. Truck has been running fine with no ping until a few days ago.
Any help is appreciated.
Jimmy
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brianj
Dodge Dakota
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11/11/2007
22:22:06
|  RE: Spark plugs and PCM's
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oil in the manifold? not good. i just replaced my pan gasket 4 days ago. basic hand tools and a few hours... not that bad. (but i am also a mechanic)i had oil in there too and a slight spark knock. and now it runs smoother than ever. but be sure to torque those plenum bolts correctly.
you probobly need to do the gasket jim.
99 318 4x4
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Jimmy9190
Dodge Dakota
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11/12/2007
16:57:15
| RE: Spark plugs and PCM's
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Thanks for the info Brian. I took a better look down the TB today in the daylight with a good flashlight and the manifold is dry. There's no oil present there but there is a very light carbon dusting which I would think is normal. The dust doesn't even cover the entire surface of the manifold. I replaced the NGK's with new 3923's and went for a test drive. There's no ping at all now and the truck is running fine. I drove on straight flat roads and up & down hills too and there is no noticeable ping. The truck holds its speed in 5th gear climbing hills and will ping just a little if I gas it to increase speed going up hills, which I would also think is normal. I had considered using Seafoam in it but I am not a big fan of additives and/or chemicals. I'll leave it just like it is for the time being. I guess my particular Dakota just runs better with the 3923's. Maybe it's the difference in the amount of copper in the plugs or some other difference that caused the ping with NGK. The same kind of problem occurred with a serpentine belt tensioner from Autozone. Two different tensioners kept slinging the belt off and I had to get the one from Napa to finally fix it. But the Napa part was built exactly the same as the OE tensioner, and the AZ part was a different design.
Thanks again.
Jimmy
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daddio
Dodge Dakota
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11/12/2007
17:25:37
| RE: Spark plugs and PCM's
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Seafoam is great for cleaning the fuel ssytem out. how did the old plugs look? you could be running a little lean. that will also cause pinging.
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Jimmy9190
Dodge Dakota
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11/12/2007
20:22:17
| RE: Spark plugs and PCM's
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Thanks Daddio,
Plugs looked great. A light tan-brownish color. Electrodes were all in good shape but one or two had increased the gap a few 1000ths. Nothing out of the ordinary, as far as I know. I may have gapped them just a little wide the last tune up I did back in January. As far as I can tell my Dakota runs well and is in tune like it should be. I have no performance mods other than I took off the snorkel and removed the rubber flap from the intake. I put an aftermarket cruise control on it and a mild audio system but other than that it's bone stock.
Jimmy
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