Tune Ups
01-31-2009, 12:48 PM
#21
Join Date: Sep 2008
Location: Illinois
Posts: 12
Today i just did that. I replaced my plugs and coils. I went with Motorcraft dg508 and NGK Iridium IX. At first #4 went bad so i did just one. Then one by one starting to go bad. I decided to just replace all at once. WOW night and day no more miss fire at cruising. Usually in 4th or 5th I'll notice it. The cheapest OEM coils i found was at http://nationalfleetparts.com/DG-508...coil-pack.aspx...... Hope this helps
01-31-2009, 12:50 PM
#22
Join Date: Sep 2008
Location: Illinois
Posts: 12
Great write up i wish i saw this first before my headaches.
How many miles on it?
The first thing to do is pull the COPs and test them with an Ohmmeter. The primary coil (the low voltage side, measure across the two terminal where the harness connects) should be 0.3Ω to 0.8Ω on a stock coil. Note that this is a very low value and many/most inexpensive multi meters are not very accurate in that range, so if it's less than 2.0Ω it's probably OK.
The secondary (high voltage) coil, measured between either of the primary pins and the spring or terminal at the bottom of the COP should be between 4.0kΩ and 10.0kΩ (4,000Ω and 10,000Ω). Typical values I have seen are 5.5kΩ to 7.0kΩ.
In may experience the most common failure is a short in the secondary coil which can be identified as a secondary resistance of less than 4.0kΩ--usually a bad secondary will read 1.5kΩ to 2.5kΩ, or open.
If the COPs test OK then yank the plugs and see what you can see, keep track of which cylinder each came from so that if there is a problem you'll at least have a clue as to where to look further.
I'd put new plugs in anyway once I had the COPs and old plugs out...
------------------------------
After market "high-energy" coils typically have lower primary coil resistance, 0.1Ω to 0.2Ω. This makes them draw more current, which equals more energy, which produces more output voltage when the field collapses--and which causes the secondary windings to fail sooner all other things being equal.
The first thing to do is pull the COPs and test them with an Ohmmeter. The primary coil (the low voltage side, measure across the two terminal where the harness connects) should be 0.3Ω to 0.8Ω on a stock coil. Note that this is a very low value and many/most inexpensive multi meters are not very accurate in that range, so if it's less than 2.0Ω it's probably OK.
The secondary (high voltage) coil, measured between either of the primary pins and the spring or terminal at the bottom of the COP should be between 4.0kΩ and 10.0kΩ (4,000Ω and 10,000Ω). Typical values I have seen are 5.5kΩ to 7.0kΩ.
In may experience the most common failure is a short in the secondary coil which can be identified as a secondary resistance of less than 4.0kΩ--usually a bad secondary will read 1.5kΩ to 2.5kΩ, or open.
If the COPs test OK then yank the plugs and see what you can see, keep track of which cylinder each came from so that if there is a problem you'll at least have a clue as to where to look further.
I'd put new plugs in anyway once I had the COPs and old plugs out...
------------------------------
After market "high-energy" coils typically have lower primary coil resistance, 0.1Ω to 0.2Ω. This makes them draw more current, which equals more energy, which produces more output voltage when the field collapses--and which causes the secondary windings to fail sooner all other things being equal.
02-19-2009, 09:30 AM
#27
1st Gear Member
Join Date: Feb 2009
Location: georgia
Posts: 70
im glad i found this write-up! i just got done pulling my coils only to find the rear pasenger side coil had water on it! that had ot have been the cause of my misfire. all coils read good and im gonna change the plugs very soon i just dont have any right now and if i drive to the store to get some my engine will be hot...mayb tomorrow i will change plugs. thanks cliffyk for that very helpful info on the resistance values!
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