Misfire No Check Engine Light
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Misfire No Check Engine Light
02 4.6 started to misfire yesterday, bought new plugs and checked all COP's with multimeter. all tested within spec according to repair manual. No signs of moisture, and plugs did not solve problem. I have to assume it is still a bad COP whether it be the coil itself or just a boot going bad. I have gotten no check engine light at all. Will I still be able to get a code scanner to tell me what cylinder has the misfire?
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Joined: Jan 2004
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From: St Louis
Taking resistance readings of COPs is a mostly worthless exercise. A simple resistance reading cannot turn up anything other than a grossyly shorted or open coil. Most misfires are due to internal arcing under the pressure of the high secondary voltage.
You have several options:
1) Get access to a scan tool that can read Mode 6 data and look at the MISFIRE counters for clues.
2) Identify the driving conditions that induce the misfire. Then, HAMMER on that condition until the CEL does come on. Then get you codes pulled with an ordinary code reader or scanner.
3) Buy one new COP. Play round-robin with it until you get the right one.
4) Buy 8 new COPS and replace them all.
Personally, I'd suggest either choice # 2 or #1.
Steve
You have several options:
1) Get access to a scan tool that can read Mode 6 data and look at the MISFIRE counters for clues.
2) Identify the driving conditions that induce the misfire. Then, HAMMER on that condition until the CEL does come on. Then get you codes pulled with an ordinary code reader or scanner.
3) Buy one new COP. Play round-robin with it until you get the right one.
4) Buy 8 new COPS and replace them all.
Personally, I'd suggest either choice # 2 or #1.
Steve
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I am going with #1 because I could not get #2 to arise yesterday. Seems stupid to me that a misfire does not cause a CEL to come on unless it is bad enough to cause damage to catalyst (atleast thats what I read).
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dathantarah
1997 - 2006 Expedition & Navigator
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Nov 6, 2007 09:37 AM
