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paulrice
User
Dec 27, 2009, 7:31 AM
Post #1 of 2
(4188 views)
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2004 cadillac seville sls 4.7 hade a po302 code last week changed spark plugs seemed ok for a day check engine on again checked and po300 codeis reading am going to pull the plugs and check also the boots how to check the coil packswhile there out i have an omh meter but what wires do icheck
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DanD
Veteran
/ Moderator
Dec 27, 2009, 10:01 AM
Post #2 of 2
(4175 views)
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It’s not that I don’t want to help with the test procedure; but it’s not all that easy to explain. We’re not given meter tests or specs for these “smart coils” (each coil has its own module) themselves; but the complete circuits. With a number of different test points; from the computer, fuse panel(s) to splice bars and just about everything in between.
Just about every test procedure that deals with misfire codes; want us to start by monitoring the misfire counters, which can only be accessed by a scan tool. This is to narrow down which cylinder(s) are intermittently misfiring. Misfire counters not codes; counters are real time numbers, shown on screen; that numerically count up from zero. Zero being no misfire detected to well into double digits when there is a misfire. The numbers do not have specific values; the higher the number the worse the misfire.
Do as you said and visually inspect the coils, coil core springs and there boots for burning. Where you unfortunate enough to buy or did you unintentionally crack a spark plug?
You could also compare the meter readings between all the coils; seeing if there isn’t one that stands out to be different?
If you can narrow down which cylinder; see if switching coils with a known good cylinder and see whether the problem follows the coil.
Also even though the ignition seems to be the most common area that causes misfires; there are a number of other things that can as well.
Plugged or failing injector, vacuum leak, plugged EGR passageway, low or high fuel pressure, engine mechanical and the list could go on and on.
Dan.
Canadian "EH"
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